biosolids applied to land
TRANSCRIPT
Biosolids Applied toLand
Advancing Standards and Practices
Committee on Toxicants and Pathogens in Biosolids Applied toLand
Board on Environmental Studies and ToxicologyDivision on Earth and Life Studies
NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES
THE NATIONAL ACADEMIES PRESSWashington DC wwwnapedu
i
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THE NATIONAL ACADEMIES PRESS 500 Fifth Street NW Washington DC 20001
NOTICE The project that is the subject of this report was approved by the Governing Board of theNational Research Council whose members are drawn from the councils of the National Academyof Sciences the National Academy of Engineering and the Institute of Medicine The members ofthe committee responsible for the report were chosen for their special competences and with regardfor appropriate balance
This project was supported by Grant No X-82862501 between the National Academy of Sci-ences and the US Environmental Protection Agency Any opinions findings conclusions orrecommendations expressed in this publication are those of the author(s) and do not necessarilyreflect the view of the organizations or agencies that provided support for this project
International Standard Book Number 0-309-08486-5
Library of Congress Control Number 2002112634Cover photograph by Robert OrsquoDette Synagro
Additional copies of this report are available from The National Academies Press 500 Fifth StreetNW Box 285 Washington DC 20055 800ndash624ndash6242 202ndash334ndash3313 (in the Washington metropoli-tan area) httpwwwnapedu
Copyright 2002 by the National Academy of Sciences All rights reserved
Printed in the United States of America
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The National Academy of Sciences is a private nonprofit self-perpetuating society of distinguished scholars engaged in scientific and engineering research dedicated to the furtherance of science and technology and to their use for the general welfare Upon the authority of the charter granted to it by the Congress in 1863 the Academy has a mandate that requires it to advise the federal government on scientific and technical matters Dr Bruce M Alberts is president of the National Academy of Sciences
The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences as a parallel organization of outstanding engineers It is autonomous in its administration and in the selection of its members sharing with the National Academy of Sciences the responsibility for advising the federal government The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs encourages education and research and recognizes the superior achievements of engineers Dr Wm A Wulf is president of the National Academy of Engineering
The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and upon its own initiative to identify issues of medical care research and education Dr Harvey V Fineberg is president of the Institute of Medicine
The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academyrsquos purposes of furthering knowledge and advising the federal government Functioning in accordance with general policies determined by the Academy the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government the public and the scientific and engineering communities The Council is administered jointly by both Academies and the Institute of Medicine Dr Bruce M Alberts and Dr Wm A Wulf are chair and vice chair respectively of the National Research Council
wwwnational-academiesorg
iii
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COMMITTEE ON TOXICANTS AND PATHOGENS INBIOSOLIDS APPLIED TO LAND
Members
THOMAS ABURKE (Chair) Johns Hopkins University Baltimore MarylandLAWRENCE RCURTIS Oregon State University Corvallis OregonCHARLES NHAAS Drexel University Philadelphia PennsylvaniaELLEN ZHARRISON Cornell University Ithaca New YorkWILLIAM EHALPERIN New Jersey Medical School Newark New JerseyJOHN BKANEENE Michigan State University East Lansing MichiganGREG KESTER Wisconsin Department of Natural Resources Madison WisconsinSTEPHEN PMCGRATH Institute for Arable Crops Research Rothamsted EnglandTHOMAS EMCKONE University of California Berkeley CaliforniaIAN LPEPPER University of Arizona Tucson ArizonaSURESH DPILLAI Texas AampM University College Station TexasFREDERICK GPOHLAND University of Pittsburgh Pittsburgh PennsylvaniaROBERT SREIMERS Tulane University New Orleans LouisianaROSALIND ASCHOOF Gradient Corporation Mercer Island WashingtonDONALD LSPARKS University of Delaware Newark DelawareROBERT CSPEAR University of California Berkeley California
Staff
SUSAN NJMARTEL Study DirectorMARK CGIBSON Program OfficerROBERTA MWEDGE Program Director for Risk AnalysisRUTH ECROSSGROVE EditorJESSICA BROCK Senior Project AssistantMIRSADA KARALIC-LONCAREVIC Research AssistantKELLY ACLARK Editorial Assistant
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rted
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ase
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his
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icat
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ibut
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vi
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ibut
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BOARD ON ENVIRONMENTAL STUDIES ANDTOXICOLOGY1
Members
GORDON ORIANS (Chair) University of Washington SeattleJOHN DOULL (Vice Chair) University of Kansas Medical Center Kansas CityDAVID ALLEN University of Texas AustinINGRID CBURKE Colorado State University Fort CollinsTHOMAS BURKE Johns Hopkins University Baltimore MarylandWILLIAM LCHAMEIDES Georgia Institute of Technology AtlantaCHRISTOPHER BFIELD Carnegie Institute of Washington Stanford CaliforniaDANIEL SGREENBAUM Health Effects Institute Cambridge MassachusettsBRUCE DHAMMOCK University of California DavisROGENE HENDERSON Lovelace Respiratory Research Institute Albuquerque
New MexicoCAROL HENRY American Chemistry Council Arlington VirginiaROBERT HUGGETT Michigan State University East LansingJAMES HJOHNSON Howard University Washington DCJAMES FKITCHELL University of Wisconsin MadisonDANIEL KREWSKI University of Ottawa Ottawa OntarioJAMES AMACMAHON Utah State University LoganWILLEM FPASSCHIER Health Council of the Netherlands The HagueANN POWERS Pace University School of Law White Plains New YorkLOUISE MRYAN Harvard University Boston MassachusettsKIRK SMITH University of California BerkeleyLISA SPEER Natural Resources Defense Council New York New York
Senior Staff
JAMES JREISA DirectorDAVID JPOLICANSKY Associate Director and Senior Program Director for
Applied EcologyRAYMOND AWASSEL Senior Program Director for Environmental Sciences and
EngineeringKULBIR BAKSHI Program Director for the Committee on ToxicologyROBERTA MWEDGE Program Director for Risk AnalysisKJOHN HOLMES Senior Staff OfficerSUSAN NJMARTEL Senior Staff OfficerSUZANNE VAN DRUNICK Senior Staff OfficerRUTH ECROSSGROVE Managing Editor
1This study was planned overseen and supported by the Board on EnvironmentalStudies and Toxicology
vii
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WATER SCIENCE AND TECHNOLOGY BOARD
Members
RICHARD GLUTHY (Chair) Stanford University Stanford CaliforniaJOAN BROSE (Vice Chair) University of South Florida St PetersburgRICHELLE MALLEN-KING Washington State University PullmanGREGORY BBAECHER University of Maryland College ParkKENNETH RBRADBURY Wisconsin Geological and Natural History Survey
MadisonJAMES CROOK CH2M Hill Boston MassachusettsEFI FOUFOULA-GEORGIOU University of Minnesota MinneapolisPETER GLEICK Pacific Institute for Studies in Development Environment and
Security Oakland CaliforniaSTEVEN PGLOSS US Geological Survey Flagstaff ArizonaJOHN LETEY JR University of California RiversideDIANE MMCKNIGHT University of Colorado BoulderCHRISTINE LMOE Emory University Atlanta GeorgiaRUTHERFORD HPLATT University of Massachusetts AmherstJERALD LSCHNOOR University of Iowa Iowa CityLEONARD SHABMAN Virginia Polytechnic Institute and State University
BlacksburgRRHODES TRUSSELL Montgomery Watson Pasadena California
Staff
STEPHEN DPARKER DirectorLAURA JEHLERS Senior Staff OfficerJEFFREY WJACOBS Senior Staff OfficerWILLIAM SLOGAN Senior Staff OfficerMARK CGIBSON Staff OfficerMJEANNE AQUILINO Administrative AssociateELLEN ADE GUZMAN Research AssociatePATRICIA JONES KERSHAW StudyResearch AssociateANITA AHALL Administrative AssistantANIKE LJOHNSON Project AssistantJON QSANDERS Project Assistant
viii
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ng-s
peci
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ting
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ever
can
not b
ere
tain
ed a
nd s
ome
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grap
hic
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rs m
ay h
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iden
tally
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rted
Ple
ase
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his
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e ve
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r attr
ibut
ion
OTHER REPORTS OF THE BOARD ONENVIRONMENTAL STUDIES AND TOXICOLOGY
The Airliner Cabin Environment and Health of Passengers and Crew (2002)Arsenic in Drinking Water 2001 Update (2001)Evaluating Vehicle Emissions Inspection and Maintenance Programs (2001)Compensating for Wetland Losses Under the Clean Water Act (2001)A Risk-Management Strategy for PCB-Contaminated Sediments (2001)Toxicological Effects of Methylmercury (2000)Strengthening Science at the US Environmental Protection Agency
Research-Management and Peer-Review Practices (2000)Scientific Frontiers in Developmental Toxicology and Risk Assessment
(2000)Copper in Drinking Water (2000)Ecological Indicators for the Nation (2000)Waste Incineration and Public Health (1999)Hormonally Active Agents in the Environment (1999)Research Priorities for Airborne Particulate Matter (3 reports 1998ndash2001)Ozone-Forming Potential of Reformulated Gasoline (1999)Risk-Based Waste Classification in California (1999)Arsenic in Drinking Water (1999)Brucellosis in the Greater Yellowstone Area (1998)The National Research Councilrsquos Committee on Toxicology The First 50
Years (1997)Carcinogens and Anticarcinogens in the Human Diet (1996)Upstream Salmon and Society in the Pacific Northwest (1996)Science and the Endangered Species Act (1995)Wetlands Characteristics and Boundaries (1995)Biologic Markers (5 reports 1989ndash1995)Review of EPArsquos Environmental Monitoring and Assessment Program (3
reports 1994ndash1995)Science and Judgment in Risk Assessment (1994)Pesticides in the Diets of Infants and Children (1993)Setting Priorities for Land Conservation (1993)Protecting Visibility in National Parks and Wilderness Areas (1993)Dolphins and the Tuna Industry (1992)Science and the National Parks (1992)Assessment of the US Outer Continental Shelf Environmental Studies
Program Volumes IndashIV (1991ndash1993)Human Exposure Assessment for Airborne Pollutants (1991)Rethinking the Ozone Problem in Urban and Regional Air Pollution (1991)Decline of the Sea Turtles (1990)Copies of these reports may be ordered from the National Academy Press(800) 624ndash6242 or (202) 334ndash3313wwwnapedu
ix
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Preface
In this report biosolids are defined as sewage sludge that has been treatedto meet the regulatory requirements for land application set out in the Code ofFederal Regulations Title 40 (Part 503) The US Environmental ProtectionAgency (EPA) established the Part 503 rule and is responsible for overseeingthe national biosolids program The land-application requirements includeconcentration limits and loading rates for chemical pollutants treatment and userequirements for controlling and reducing pathogens and the attraction ofvectors and management practices The requirements are intended to protectpublic health and the environment from any reasonably anticipated adverseeffects Over the past decade questions have been raised about the adequacy ofthe chemical and pathogen standards for protecting public health To helpaddress the questions and the requirement for periodic reassessment of the Part503 rule EPA asked the National Research Council (NRC) to independentlyreview the technical basis of the chemical and pathogen regulations forbiosolids focusing only on human health
In this report the NRCrsquos Committee on Toxicants and Pathogens inBiosolids Applied to Land (membership and biographical information providedin Appendix A) searched for evidence on human health effects related tobiosolids exposure and the technical methods and approaches used by EPA toestablish its human-health-based chemical and pathogen standards for biosolidsThe NRC and the committee are aware that some interested parties wereanticipating that this report might make a determination of whether EPA shouldcontinue to promote land application of biosolids However such a
PREFACE xi
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ng s
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ther
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ng-s
peci
fic fo
rmat
ting
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ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
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determination was not part of the committeersquos charge The committee agreesthat regulations must be adequate to protect human health and the environmentand that they must be complied with and enforced The committee was asked tofocus its review on approaches for identifying human health hazards forassessing exposure to those hazards and for assessing risk from the exposuresThis report offers numerous recommendations to update and strengthen thescientific credibility of the biosolids regulations and to ensure their consistentimplementation
This report has been reviewed in draft form by individuals chosen for theirdiverse perspectives and technical expertise in accordance with proceduresapproved by the NRCrsquos Report Review Committee The purpose of thisindependent review is to provide candid and critical comments that will assistthe institution in making its published report as sound as possible and to ensurethat the report meets institutional standards for objectivity evidence andresponsiveness to the study charge The review comments and draft manuscriptremain confidential to protect the integrity of the deliberative process We wishto thank the following individuals for their review of this report Robert CooperBioVir Laboratories Inc Benicia California Alison Cullen University ofWashington Seattle Washington Charles Henry University of WashingtonSeattle Washington Cecil Lue-Hing Cecil Lue-Hing amp Associates Inc BurrRidge Illinois Philip Landrigan Mount Sinai School of Medicine New YorkNew York Aaron Margolin University of New Hampshire Durham NewHampshire Penny Newman Center for Community Action and EnvironmentalJustice Riverside California George OrsquoConnor University of FloridaGainesville Florida Robert Southworth Marshall Virginia Alan Stern NewJersey Department of Environmental Protection Trenton New Jersey WillyVerstraete University of Gent Gent Belgium and William Yanko Big BearCity California
Although the reviewers listed above have provided many constructivecomments and suggestions they were not asked to endorse the conclusions orrecommendations nor did they see the final draft of the report before its releaseThe review of this report was overseen by Michael Kavanaugh Malcolm PirnieInc Emeryville California and Ronald Estabrook University of TexasSouthwestern Medical Center Dallas Texas Appointed by the NRC they wereresponsible for making certain that an independent examination of this reportwas carried out in accordance with institutional procedures and that all reviewcomments were carefully considered Responsibility for the final content of thisreport rests entirely with the authoring committee and the institution
The committee gratefully acknowledges the individuals who madepresentations to the committee at its public meetings A list of those individuals is
PREFACE xii
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provided in Appendix B The committee also wishes to thank EPA staffmembers Alan Hais Robert Bastian Alan Rubin James Smith and CharlesWhite for their assistance in providing documents and information
The committee is grateful for the assistance of the NRC staff in preparingthe report It particularly wishes to acknowledge the contributions of SusanMartel project director who coordinated the project and contributed to thecommitteersquos report Other staff members who contributed to this effort areJames JReisa director of the Board on Environmental Studies and ToxicologyRoberta MWedge program director for risk analysis Mark Gibson programofficer (Water Science and Technology Board) Ruth ECrossgrove editorMirsada Karalic-Loncarevic research assistant and Jessica Brock seniorproject assistant
Finally I would especially like to thank all the members of the committeefor their efforts throughout the development of this report
Thomas ABurke PhD Chair Committee
on
Toxicants and Pathogens in Biosolids
Applied to Land
PREFACE xiii
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PREFACE xiv
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Contents
ABBREVIATIONS xviii
SUMMARY 1
1 INTRODUCTION 17 Biosolids 18 Human Health and Risk-Assessment Issues 25 The Committeersquos Task 26 The Committeersquos Approach 27 Report Organization 29 References 29
2 BIOSOLIDS MANAGEMENT 31 Federal Biosolids Regulations and Current State of Program 35 European Biosolids Management 55 Pathogen Issues and Treatment Controls 74 Pathogen Equivalency Committee 80 Implementation and End-Use Practices 82 Characterization of Biosolids 91 Compliance Assistance and Enforcement 95 Findings and Recommendations 96 References 99
CONTENTS xv
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3 EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTSASSOCIATED WITH BIOSOLIDS PRODUCTION ANDAPPLICATION
106
Description of the Literature 107 Findings and Recommendations 121 References 122
4 ADVANCES IN RISK ASSESSMENT SINCE THE ESTAB-LISHMENT OF THE PART 503 RULE
126
The Risk-Assessment Process 126 New Approaches and Considerations in Risk Assessment 130 Changes in Risk-Assessment Approaches in EPA Offices 147 Findings and Recommendations 156 References 158
5 EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMI-CAL STANDARDS
164
Hazard Assessment and Chemical Selection 165 Exposure Assessment 178 Derivation of Risk-Based Standards 205 Inorganic Chemicals 207 Organic Chemicals 219 Findings and Recommendations 238 References 242
6 EVALUATION OF EPArsquoS APPROACH TO SETTINGPATHOGEN STANDARDS
257
Pathogen Standards 257 Pathogens in Biosolids 267 Exposure to Pathogens 279 Host Factors 287 Exposure to Workers 289 Antibiotic Resistance 290 Pathogen Risk Assessment 291 Findings and Recommendations 303 References 306
7 INTEGRATION OF CHEMICAL AND PATHOGEN RISKASSESSMENT
322
Agent-By-Agent Risk Assessment 322 Secondary Transmission 324
CONTENTS xvi
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Complex Mixtures 327 Findings and Recommendations 331 References 333
GLOSSARY 335
APPENDIXES
A Biographical Information on the Committee on Toxicants andPathogens in Biosolids Applied to Land
338
B Participants at Public Sessions 344
CONTENTS xvii
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Abbreviations
CFR Code of Federal Regulations
CFU colony forming units
CWA Clean Water Act
EQ exceptional quality
HEI highly exposed individual
MEI most exposed individual
MPN most probable number
MT metric tons
NIOSH National Institute for Occupational Safety and Health
NRC National Research Council
NSSS National Sewage Sludge Survey
OIG EPA Office of Inspector General
PCBs polychlorinated biphenyls
PEC Pathogen Equivalency Committee
PFRP process to further reduce pathogens
PFU plaque-forming unit
POTW publicly owned treatment works
PSRP process to significantly reduce pathogens
QMRA quantitative microbial risk assessment
RME reasonable maximum exposure
TEF toxicity equivalency factor
TS total solids
ABBREVIATIONS xviii
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xix
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Biosolids Applied to Land Advancing Standardsand Practices
xx
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Summary
Wastewater treatment in the United States is a major cornerstone of effortsto keep the nationrsquos waters clean Sewage sludge is the solid semisolid orliquid residue generated during treatment of domestic sewage Since the early1970s the US Environmental Protection Agency (EPA) and the wastewatertreatment industry have promoted recycling of sewage sludge With theprohibition of ocean disposal of wastewater residuals in 1992 the use of sewagesludge as soil amendments (soil conditioners or fertilizers) or for landreclamation has been increased to reduce the volume of sewage sludge thatmust be landfilled incinerated or disposed of at surface sites Approximately56 million dry tons of sewage sludge are used or disposed of annually in theUnited States approximately 60 of that is used for land applicationDepending on the extent of treatment sewage sludge may be applied wherelittle exposure of the general public is expected to occur on the sites such as onagricultural land forests and reclamation sites or on public-contact sites suchas parks golf courses lawns and home gardens EPA estimates that sewagesludge is applied to approximately 01 of available agricultural land in theUnited States on an annual basis
The regulation governing land application of sewage sludge wasestablished by EPA in 1993 in the Code of Federal Regulations Title 40 (Part503) under Section 405 (d) of the Clean Water Act The regulation is intendedto protect public health and the environment The Part 503 rule establishedmanagement practices for land application of sewage sludge concentrationlimits and loading rates for chemicals and treatment and use requirements
SUMMARY 1
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designed to control and reduce pathogens and attraction of disease vectors(insects or other organisms that can transport pathogens) In this report the termbiosolids refers to sewage sludge treated to meet the land-application standardsin the Part 503 rule or any other equivalent land-application standards
The chemical and pathogen land-application standards in the Part 503 rulewere developed differently For chemicals EPA conducted extensive riskassessments that involved identifying the chemical constituents in biosolidsjudged likely to pose the greatest hazard characterizing the most likelyexposure scenarios and using scientific information and assumptions tocalculate concentration limits and loading rates (amount of chemical that can beapplied to a unit area of land) Nine inorganic chemicals in biosolids arecurrently regulated and EPA is considering the addition of a class of organicchemicals (dioxins) to its regulation Monitoring data on some of the regulatedinorganic chemicals indicate a decrease in their concentrations over the pastdecade due in part to the implementation of wastewater pretreatment programsThus the chemical limits for biosolids can be achieved easily In contrast to thechemical standards the pathogen standards are not risk-based concentrationlimits for individual pathogens but are technologically based requirementsaimed at reducing the presence of pathogens and potential exposures to them bytreatment or a combination of treatment and use restrictions Monitoringbiosolids is required for indicator organisms (certain species of organismsbelieved to indicate the presence of a larger set of pathogens)
THE COMMITTEErsquoS TASK
In response to the Clean Water Act requirement to reassess periodically thescientific basis of the Part 503 rule and to address public-health concerns EPAasked the National Research Council (NRC) to conduct an independentevaluation of the technical methods and approaches used to establish thechemical and pathogen standards for biosolids focusing specifically on humanhealth protection and not ecological or agricultural issues The NRC convenedthe Committee on Toxicants and Pathogens in Biosolids Applied to Landwhich prepared this report The committee was asked to perform the followingtasks
1 Review the risk-assessment methods and data used to establishconcentration limits for chemical pollutants in biosolids todetermine whether they are the most appropriate approachesConsider the NRCrsquos previous (1996) review and determine whetherthat reportrsquos recommendations have
SUMMARY 2
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ng-s
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been appropriately addressed Consider (a) how the relevantchemical pollutants were identified (b) whether all relevantexposure pathways were identified (c) whether exposure analysesparticularly from indirect exposures are realistic (d) whether thedefault assumptions used in the risk assessments are appropriateand (e) whether the calculations used to set pollutant limits areappropriate
2 Review the current standards for pathogen elimination in biosolidsand their adequacy for protecting public health Consider (a)whether all appropriate pathogens were considered in establishingthe standards (b) whether enough information on infectious doseand environmental persistence exists to support current controlapproaches for pathogens (c) risks from exposure to pathogensfound in biosolids and (d) new approaches for assessing risks tohuman health from pathogens in biosolids
3 Explore whether approaches for conducting pathogen riskassessment can be integrated with those for chemical riskassessment If appropriate recommend approaches for integratingpathogen and chemical risk assessments
MAJOR FINDINGS AND RECOMMENDATIONS
The committee recognizes that land application of biosolids is a widelyused practical option for managing the large volume of sewage sludgegenerated at wastewater treatment plants that otherwise would largely need tobe disposed of at landfills or by incineration In responding to its charge thecommittee searched for evidence on human health effects related to biosolidsexposure reviewed the risk assessments and technical data used by EPA toestablish the chemical and pathogen standards and reviewed the managementpractices of the Part 503 rule The committee did not attempt to determinewhether the approaches used by EPA to set the 1993 biosolids standards wereappropriate at the time of their development and the committeersquos findings andrecommendations should not be construed as either criticism or approval of thestandards issued at that time The committee found that EPA has not yetaddressed certain recommendations of the 1996 NRC report that pertain to thescope of the present study The committee is aware that some interested partieswere anticipating that this report might make a determination of whether EPAshould continue to promote land application of biosolids However such adetermination was not part of the committeersquos charge Nor was the committeeasked to judge the adequacy of the individual standards in protecting humanhealth The committeersquos report instead is focused on identifying how currentrisk-assessment practices and knowledge regarding chemi
SUMMARY 3
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cals and pathogens in biosolids can be used to update and strengthen thescientific basis and credibility of EPArsquos biosolids regulations
In this report the committee documents numerous findings and a numberof recommendations for addressing public-health concerns uncertainties anddata gaps about the technical basis of the biosolids standards To delineateissues needing the greatest attention the committee identified the followingoverarching findings and recommendation based on its review and synthesis ofthe specific findings and recommendations of each chapter
Overarching Findings
There is no documented scientific evidence that the Part 503 rule has failedto protect public health However additional scientific work is needed to reducepersistent uncertainty about the potential for adverse human health effects fromexposure to biosolids There have been anecdotal allegations of disease andmany scientific advances have occurred since the Part 503 rule waspromulgated To assure the public and to protect public health there is a criticalneed to update the scientific basis of the rule to (1) ensure that the chemical andpathogen standards are supported by current scientific data and risk-assessmentmethods (2) demonstrate effective enforcement of the Part 503 rule and (3)validate the effectiveness of biosolids-management practices
Overarching Recommendations
bull Use improved risk-assessment methods to better establish standardsfor chemicals and pathogens Risk-assessment methods for chemicalsand pathogens have advanced over the past decade to the extent that (1)new risk assessments should be conducted to update the scientific basis ofthe chemical limits and (2) risk assessments should be used tosupplement technological approaches to establishing regulatory criteriafor pathogens in biosolids
bull Conduct a new national survey of chemicals and pathogens in sewagesludge The committee endorses the recommendation of a previous NRCcommittee that a new national survey of chemicals be performed Thecommittee further recommends a survey of pathogen occurrence in rawand treated sewage sludges The survey should include a carefulexamination of management practices to ensure that risk-assessmentprinciples are effectively translated into practice Data from the surveyshould be used to provide feedback for continuous improvement in thescience and technology of biosolids applied to land
SUMMARY 4
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bull Establish a framework for an approach to implement human healthinvestigations A procedural framework should be established toimplement human health investigations including short-terminvestigations of unusual episodes of release exposure or disease andlarge-scale preplanned studies of exposures and their association if anywith disease The framework should have mechanisms to document state-of-the-art successes both technological and administrative in preventingor remediating exposure to pathogens and toxicants and their adversehealth outcomes Further the framework should include a means fortracking allegations and sentinel events (compliance management orhealth based) investigations and conclusions Such tracking should besystematic and developed in cooperation with states
bull Increase the resources devoted to EPArsquos biosolids program Toremedy the deficiencies and to implement the recommendations describedin this report more funding and staff resources are needed for EPArsquosbiosolids program EPA should support and facilitate greater delegation ofauthority to states to administer the federal biosolids regulationResources are also needed for conducting needed research and to revisethe regulation as appropriate and in a timely fashion
These recommendations are discussed in greater detail below and in thefollowing chapters
Health Effects
Toxic chemicals infectious organisms and endotoxins or cellular materialmay all be present in biosolids There are anecdotal reports attributing adversehealth effects to biosolids exposures ranging from relatively mild irritant andallergic reactions to severe and chronic health outcomes Odors are a commoncomplaint about biosolids and greater consideration should be given to whetherodors from biosolids could have adverse health effects However a causalassociation between biosolids exposures and adverse health outcomes has notbeen documented To date epidemiological studies have not been conducted onexposed populations such as biosolids appliers farmers who use biosolids ontheir fields and communities near land-application sites Because of theanecdotal reports of adverse health effects the public concerns and the lack ofepidemiological investigation the committee concluded that EPA shouldconduct studies that examine exposure and potential health risks to worker andresidential populations Studies of wastewater treatment workers exposed to rawsewage sludge should not be used as substitutes for studies of populationsexposed to biosolids The types and routes of exposure to sewage sludge andbiosolids constituents can be quite different and there are major differences inthe populations exposed For example exposures to
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biosolids go beyond the wastewater treatment plant to other worker populationssuch as appliers and farmers and to the general public such as communitiesliving near land-application sites and consumers of crops grown on biosolids-amended soils Exposed populations may also include sensitive subpopulationssuch as children immunocompromised individuals and the elderly who areunlikely to be prevalent in the workplace
Findings There is a lack of exposure and health information onpopulations exposed to biosolids Therefore although the land application ofbiosolids has occurred for many years with little if any systematic documentedevidence of adverse effects there is a need to gather epidemiological data andto investigate allegations of health incidents EPA needs to study morerigorously the exposure and health risks or the lack thereof in worker andcommunity populations exposed to biosolids
Recommendations Although routine human health surveillance of allpopulations exposed to biosolids is impractical the committee recommends thatEPA promote and support response investigations targeted exposuresurveillance studies and a few well-designed epidemiological investigations ofexposed populations This recommendation is intended to provide a means ofdocumenting whether health effects exist that can be linked to biosolidsexposure The committee recommends the following types of studies
bull Studies in response to unusual exposures and unusual occurrences ofdisease Occasionally the occurrence of unusual events can provideinformation on the agents of disease For example an outbreak or asymptom of disease might occur following a known exposure or anunusual exposure scenario In both instances exposure and healthoutcomes should be determined
bull Preplanned exposure-assessment studies Such studies should characterizethe exposures of workers such as biosolids appliers and farmers and thegeneral public who come into contact with constituents of biosolids eitherdirectly or indirectly The studies would require identification ofmicroorganisms and chemicals to be measured selection of measurementmethods for field samples and collection of adequate samples inappropriate scenarios A possible exposure-assessment study would be tomeasure endotoxin exposure of workers at biosolids production andapplication sites and of communities nearby
bull Complete epidemiological studies of biosolids use These studies shouldbe conducted to provide evidence of a causal association or a lackthereof between biosolids exposure and adverse human health effectsThey should include an assessment of the occurrence of disease and anassessment or measurement of potential exposures An example of alongitudinal epidemic
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logical study would be an evaluation of health effects in a cohort ofbiosolids appliers These workers should be characterized by duration andlevel of exposure and given appropriate follow-up Because completeepidemiological studies are expensive and require extensive data analysispriority should be given to studies that can address serious or widespreadproblems and help reduce uncertainty
Chemical and Pathogen Standards
EPArsquos 1993 chemical and pathogen standards for biosolids were based onthe scientific and technical information available at that time and theexpectation that the prescribed biosolids-management practices specified in thePart 503 rule would be effective in preventing harmful exposure to biosolidsconstituents To assure the public that the standards are protective of humanhealth it is important that EPA demonstrate that its chemical limits andpathogen-reduction requirements are supported by current scientific data andrisk-assessment methods Management practices (eg 10-meter setback fromwater bodies) are designed to control the potential risks therefore it isimportant to verify the effectiveness of the practices In addition EPA mustdemonstrate that the Part 503 rule is being enforced
Findings The committee found that no substantial reassessment has beendone to determine whether the chemical or pathogen standards promulgated in1993 are supported by current scientific data and risk-assessment methods Inaddition EPA does not have an adequate program to ensure compliance withthe biosolids regulations and has not documented the effectiveness of itsprescribed management practices Although there is no documented scientificevidence that the Part 503 rule has failed to protect public health there is a needto address scientific and management questions and uncertainties that challengeEPArsquos biosolids standards
Recommendations EPA should expand its biosolids oversight activities toinclude procedures for (1) assessing the reliability of the biosolids treatmentprocesses (2) monitoring compliance with the chemical and pathogenstandards (3) conducting environmental hazard surveillance and (4) studyinghuman exposure and health The committee recommends that Figure S-1 beused by EPA as a framework for establishing such a program The central partof the figure presents the general process by which biosolids are produced andused for land application Depicted on the left side of the figure areopportunities for conducting environmental hazard surveillance At these
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FIGURE S-1 Processing transport and land application of biosolids withoptions for hazard surveillance and studies of human exposures
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stages biosolids or environmental samples should be collected andanalyzed to verify that (1) treatment technologies for pathogen control areeffective (quality control) (2) chemical standards are met (compliance audits)and (3) unanticipated hazards are identified An important part of thisverification process is a review of the management practices required for landapplication because the practices are predicated on the assumption thatexposure to hazardous agents is further reduced by the implementation of suchpractices Studies should be conducted to determine whether the managementpractices specified in the Part 503 rule achieve their intended effect Additionalrisk-management practices should be considered in revising the Part 503 ruleConsiderations should include setbacks to residences or businesses setbacks toprivate and public water supplies limitations on holding or storage practicesslope restrictions soil permeability and depth to groundwater or bedrock andgreater distance to surface water
The right side of the figure depicts the various points in the process wherehuman exposures can occur Field research should be conducted to assesspotential exposure to biosolids constituents of concern Results from thisresearch could be used to identify populations that should be monitored orstudied at particular times and locations for abnormal health conditions andpotential biosolids exposure (see earlier recommendations for response andepidemiological studies) Studying environmental samples and reports ofadverse health outcomes can provide feedback to support or improve the risk-assessment and risk-management processes
The major aspect of the framework studied by the committee was thetechnical basis of the 1993 chemical and pathogen land-application standards ofthe Part 503 rule Recent EPA guidance recommends that risk assessment ofcomplex mixtures ideally be based on studies of the mixture rather than onselected individual components Such an approach is not feasible for biosolidshowever because studies of biosolids as complex mixtures are lackingFurthermore although methods for conducting risk assessments of chemicalmixtures are available no work has been done on risks from pathogen mixturesmuch less chemical-pathogen mixtures
Finding Because of data gaps and lack of risk-assessment methods forcomplex mixtures it is not possible at this time to integrate pathogen riskassessment with chemical risk assessment Thus it remains necessary to use acomponent-based approach to assessing risks from chemicals and pathogens inbiosolids There have been substantial improvements in conducting riskassessments since the Part 503 rule was promulgated and guidance for usingthese improved methods to update and strengthen the scientific basis of thechemical and pathogen standards is provided below
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Chemical Standards
In developing the original (1993) Part 503 rule EPA selected 10 inorganicchemicals (arsenic cadmium chromium1 copper lead mercurymolybdenum2 nickel selenium and zinc) to regulate for land application Riskassessments were conducted on each chemical to establish concentration limitsand loading rates However methods for conducting risk assessments haveevolved substantially since the 1993 regulations were established One of themajor developments has been a growing recognition of the need to includestakeholders in the risk-assessment process Stakeholders are groups who arepotentially affected by the risk groups who will manage the risk and groupswho will be affected by efforts to manage the source of the risk Stakeholderscan provide information and insights into how biosolids are used in practice andthe nature of potential exposures to chemicals and pathogens Involvingstakeholders throughout the risk-assessment process provides opportunities tobridge gaps in understanding language values and perspectives and to addressconcerns of affected communities Other important developments in riskassessment in recent years include improvements in measuring and predictingadverse health effects advancements in measuring and predicting exposureexplicit treatment of uncertainty and variability and improvements indescribing and communicating risk
In developing its 1993 chemical standards EPA selected chemicalsexposure conditions and risk-assessment assumptions that were intended to berepresentative and conservative enough to be applicable to all regions of theUnited States and to all land-application sites including agricultural fieldsforests and reclamation sites Thus the standards were expected to account forpossible variations in biosolids composition geographic and environmentalconditions or application and management practices EPA relied heavily on its1988ndash1989 National Sewage Sludge Survey (NSSS) to identify chemicals toregulate using percent detection and concentration values to exempt some
1Chromium was deleted from the regulation in 1995 This amendment was the resultof a petition seeking review of the pollutant limits for chromium filed in 1993 by theLeather Industries of America Inc to the US Circuit Court of Appeals for the Districtof Columbia Circuit The court remanded the request to EPA for additional justificationor modification of its chromium regulations in the Part 503 rule The agencysubsequently determined that there was insufficient support for regulating chromium inbiosolids
2Standards for molybdenum were dropped from the original regulation Currentlyonly a ceiling-concentration limit is available for molybdenum and a decision aboutestablishing new pollutant limits for this metal has not been made
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chemicals from regulation and to establish ceiling-concentration limits forothers A 1996 NRC report (Use of declaimed Water and Sludge in Food Crop Production) questioned the reliability of the results of the NSSS because oflimitations in sampling analyses and data-reporting methods Improvements inindustrial wastewater pretreatment processes and changes in chemical uses haveoccurred over the past decade Chemicals not included in the NSSS analyseshave since been identified as potential concerns and data gaps on toxicity andfate and transport characteristics that prevented risk assessment from beingperformed on some chemicals a decade ago might now be filled In addition thecommittee found no adequate justification for EPArsquos decision to eliminate fromregulation all chemicals detected at less than 5 frequency in the NSSS (or10 frequency in subsequent reanalysis) It should be noted that there are stilldata gaps that will continue to limit risk-assessment capability on many of thechemicals including those newly identified as potential concerns
EPA considered 14 major exposure pathways in setting the 1993 limits forthe nine regulated chemicals Nine of the pathways resulted in exposure tohumans two to animals two to soil organisms and one to plants The pathwayswere evaluated for agricultural and nonagricultural application scenarios For allnine of the regulated chemicals agricultural scenarios produced the lowestlimits that were subsequently used in the regulation EPA elected to evaluate thehuman exposure pathways for a theoretical highly exposed individual (HEI)(ie a hypothetical individual assumed to remain for an extended period of timeat or adjacent to the site where maximum exposure occurs) The degree ofrealism for the HEI varied among the exposure pathways and it was not clear tothe committee whether exposure estimates were comparably conservative for allpathways Moreover each pathway was evaluated independently and noconsideration was given to exposure from multiple pathways
Current risk-assessment practice is to perform comprehensivemultipathway risk assessments that estimate aggregate exposures for eachreceptor population (ie groups with potential exposure to contaminatedmedia) Such risk assessments are based on a conceptual site model thatidentifies the biosolids sources (eg biosolids tilled into soil or applied to thesurface for agricultural soil) the pathways by which biosolids constituentsmight be released and transported and the nature of human contacts with theconstituents General practice has changed from using the HEI as the receptorof concern because such an individual is unlikely to exist to using anindividual with reasonable maximum exposure (RME) An RME individual is ahypothetical individual who experiences the maximum exposure that isreasonably expected to occur (ie an upper-bound exposure estimate) RMEs
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should be based on receptor populations of concern such as a farm familyliving adjacent to and downhill from a land application site
A number of risk algorithms were used to calculate the 1993 chemicallimits The general algorithms are still valid but some fate and transport modelsand exposure parameter assumptions used in the calculations have advancedsince 1993 and some alternative assumptions have been supported by newstudies Chemical limits should be based on an integrated evaluation of allexposure pathways that might affect the identified receptors
Findings The committee found the technical basis of the 1993 chemicalstandards for biosolids to be outdated EPA has not reevaluated its chemicalstandards since promulgation so the data and methods used for the originalregulations are well over a decade old There have been substantial advances inrisk assessment since then and there are new concerns about some adversehealth outcomes and chemicals not originally considered Because of thediversity of exposed populations environmental conditions and agriculturalpractices in the United States it is important that nationwide chemicalregulations be based on the full range of exposure conditions that might occurFurthermore there is a need to investigate whether the biosolids produced todayare similar in composition to those used in the original assessments
Recommendations Using current risk-assessment practices EPA shouldreassess the standards for the regulated chemicals and conduct another chemicalselection process to determine whether additional chemicals should beconsidered for regulation On the basis of the revised risk assessments andchemical selection EPA can determine whether the standards or risk-management process should be revised and whether additional chemicalsshould be regulated Because the land-application standards are to be relevantnationally it is important that the revised risk assessments reflect regionalvariations in climate hydrology and biosolids use and characteristics and thatstandards are protective of populations reflecting reasonable estimates ofmaximum exposure The chemical standards should be reevaluated and updatedperiodically to ensure that they are supported by the best available scientificdata and methods Important elements for updating the risk assessments are thefollowing
bull As recommended by an earlier NRC committee a new national survey ofchemicals in biosolids should be conducted EPA should review availabledatabases from state programs in designing a new survey Other elementsthat should be included in the survey are an evaluation of the adequacy ofdetection methods and limits to support risk assessment consideration ofchemical categories such as odorants and pharmaceuticals that were notpreviously
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evaluated and assessment of the presence of multiple species of certainmetals such as mercury and arsenic that have different toxicity endpoints Data from this survey should be used to identify any additionalchemicals for potential regulation
bull Aggregate exposure assessments should be performed A conceptual sitemodel should be used to identify major and minor exposure pathways forvarious application scenarios Special consideration should be given toidentifying the application practices and environmental conditions that arelikely to result in the greatest human exposure Risks from long-term low-level exposures as well as short-term episodic exposures such as thosethat can occur with volatile chemicals should be evaluated
bull An RME individual rather than an HEI should be evaluated for eachexposure pathway Use of the RME is a more informed and reasonableestimate of exposure than the HEI because it reduces reliance on thesubjective application of default assumptions and reflects improvedmethods of characterizing population exposure When the RMEindividual is likely to be exposed by more than one pathway exposuresshould be added across pathways
bull Fate and transport models and exposure parameter assumptions used inthe risk assessment should be updated to reflect the most currentinformation on the RME individual for each exposure pathway
bull Representatives of stakeholders should be included in the risk-assessmentprocess to help identify exposure pathways local conditions that couldinfluence exposure and possible adverse health outcomes
Pathogen Standards
Pathogens are disease-causing microorganisms The two land-applicationclassifications for biosolids Class A and Class B are based on pathogencontent Class A biosolids have pathogen densities below specified detectionlimits whereas Class B biosolids have pathogen densities above those limitsNo risk assessments were conducted to establish the 1993 pathogen standardsfor these classes Instead EPA established technologically based requirementsto reduce the presence of pathogens by treatment or a combination of treatmentand use restrictions To meet Class A requirements demonstration of pathogenreduction is required by using one of several prescribed treatments Monitoringof indicator organisms is required of Class A biosolids at the time of usedistribution or land application to verify that treatment processes have reducedpathogen concentrations as expected (ie below the specified detection limits)Class B biosolids must also undergo treatment to reduce the presence ofpathogens but unlike Class A biosolids Class B biosolids may
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have detectable concentrations of pathogens Because of that site restrictionsare required to minimize contact with the biosolids until environmental factors(eg heat and desiccation) have further reduced the presence of pathogens Siterestrictions include restrictions on crop harvesting animal grazing and publicaccess for designated periods of time However there is no requirement that on-site measurements be taken at Class B application sites to confirm that thetreatment and the use restrictions resulted in below-detection pathogenconcentrations Such on-site measurements would help to estimate potentialrisks and the efficacy of site-management requirements
EPA considered a spectrum of bacteria viruses protozoa and helminths insetting its 1993 pathogen standards New information on some of these andother organisms are now available for updating hazard identification Humansmay be exposed to pathogens in biosolids from ingestion of contaminated foodwater or soil dermal contact and inhalation of bioaerosols (aerosolizedbiological particles) There is also the potential for humans to be exposed viasecondary transmission from exposure to pathogens shed from infectedindividuals either by direct contact or by routes through the environment Someexposure pathways such as the inhalation pathway were not adequatelyevaluated by EPA in the development of the 1993 Part 503 pathogenrequirements EPA also did not address sufficiently the potential for surface-water contamination by runoff groundwater contamination and secondarytransmission of disease
The reliability of biosolids treatment processes in reducing pathogens isessential for public-health protection There is a need to better document thereliability of EPArsquos prescribed treatment processes and to establish thatmanagement controls intended to reduce pathogens by natural attenuation areeffective An important consideration in making these determinations isensuring that the pathogen detection methods used are accurate and preciseSubstantial advances in detection and quantification of pathogens in theenvironment have been made since the 1993 promulgation of the Part 503 ruleFor example new molecular techniques for detecting pathogens (egpolymerase chain reaction) are now available In addition new approaches toenvironmental sample collection and processing are available Howeverimproved standardized methods for measuring pathogens in biosolids andbioaerosols need to be developed
As with the chemical standards EPA based its 1993 pathogen standards onselected pathogens and exposure conditions that were expected to berepresentative and conservative enough to be applicable to all areas of theUnited States and all types of land applications This includes the recognitionthat pathogen survival in soils can range from hours to years depending on thespecific pathogens biosolids application methods and rates initial patho
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gen concentrations soil composition and meteorological and geologicalconditions Little is know about pathogen transport and survival in bioaerosolsQuantitative microbial risk-assessment (QMRA) methods similar to those usedin chemical assessments have been developed for microbial agents in drinkingwater and food These methods are not as well established as those forchemicals and there are important differences between the two One of themajor differences is that microbial risk assessment must include the possibilityof secondary transmission of disease either through person-to-person contact orfrom transmission of the pathogen to others through air food or water Theimportance of secondary transmission depends in part on the level of acquiredimmunity to the pathogen in the community a phenomenon that has no analogin chemical risk assessment
Findings Given the variety of pathogens that have the potential to bepresent in biosolids the committee supports EPArsquos approach to establishingpathogen reduction requirements and monitoring indicator organisms Howeverthe reliability of EPArsquos prescribed treatment techniques should be betterdocumented using current pathogen detection technology and more research onenvironmental persistence and dose-response relationships is needed to verifythat current management controls for pathogens are adequate to maintainminimal exposure concentrations over an extended period of time QMRAmethods have developed sufficiently to provide better risk information thatshould be used to establish or support existing regulatory criteria
Recommendations
bull EPA should conduct a national survey of pathogen occurrence in raw andtreated sewage sludges Important elements in conducting the surveyinclude use of consistent sampling methods analysis of a broad spectrumof pathogens that could be present in sewage sludge and use of the bestavailable (preferably validated) pathogen measurement techniques
bull QMRAs should be developed and used to establish regulatory criteria(treatment requirements use restrictions and monitoring) for pathogensin biosolids For example EPA could stipulate an acceptable risk level fora particular pathogen QMRA could then be used to estimate theconcentration of that pathogen in biosolids either at the point ofapplication (where there is immediate potential for exposure) or followingany required holding period EPA could then determine experimentallybased relationships between the maximum acceptable pathogenconcentration and the process conditions (eg time temperature pHchemical doses and holding times) andor the pathogen indicatorconcentrations (either density or reduction through treatment) On thebasis of those relationships regulatory criteria and monitoring for land
SUMMARY 15
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application can be updated or developed to ensure consistent attainmentof target pathogen concentrations To conduct QMRAs a conceptual sitemodel should be used to identify all potential routes of exposureadditional input data (eg dose-response and pathogen-survival data)should be collected and consideration should be given to potentialsecondary transmission of infectious disease QMRAs also can be used toanalyze sensitivity and to ascertain what critical information is needed toreduce uncertainty about the risks from exposure to pathogens inbiosolids The pathogen standards should be reevaluated and updatedperiodically to ensure that they are supported by the best availablescientific data and methods and to ensure that anecdotal information is notbeing used for the predication of past current or future regulations
bull EPA should foster development of standardized methods for measuringpathogens in biosolids and bioaerosols
bull EPA should promote research that uses improved pathogen detectiontechnology to better establish the reliability of its prescribed pathogentreatment processes and biosolids-use controls to achieve and maintainminimal exposure over time In setting pathogen treatment requirementsit might be useful to establish metrics for typical (mean) treatmentperformance and concentrations not to be exceeded
bull Research should be conducted to assess whether other indicatororganisms such as Clostridium perfringens could be used in regulationof biosolids Such indicators along with traditional indicators andoperational parameters may be suitable for monitoring day-to-dayregulatory compliance
SUMMARY 16
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ay h
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1
Introduction
Land application of treated sewage sludge (often referred to as biosolids)for soil-amendment and land-reclamation purposes has increased over the pastdecade as a result of the ban on ocean dumping of wastewater residuals (OceanDisposal Ban Act of 1988) and as an alternative to other disposal options suchas landfilling or incineration Recycling sewage sludge has been practiced formany decades In 1993 EPA promulgated Standards for the Use or Disposal ofSewage Sludge (Code of Federal Regulations Title 40 Part 503) which setpollutant limits operational standards for pathogen and vector-attractionreduction management practices and other provisions intended to protectpublic health and the environment from any reasonably anticipated adverseeffects from chemical pollutants and pathogenic organisms Many of theregulations (commonly referred to as the Part 503 rule) were based on riskassessments conducted to identify and characterize risks associated with the useor disposal of sewage sludge In this report the National Research Councilrsquos(NRCrsquos) Committee on Toxicants and Pathogens in Biosolids Applied to Landreviews the nature of the human health risks from chemicals and pathogens inbiosolids evaluates the scientific approaches that EPA used to establish itshuman-health-based land-application pollutant limits and pathogen reductiontechniques provides an overview of the advances in risk assessment since theestablishment of those standards and in light of the advancementsrecommends risk-based strategies for reevaluating the human-health-based land-application standards of the Part 503 rule
INTRODUCTION 17
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This chapter briefly reviews why biosolids are a public-health concernstates the task addressed by the committee sets forth the committeersquos activitiesand deliberative process in developing the report and describes the organizationof the report
BIOSOLIDS
Definitions and Use
Sewage sludge is defined in the Part 503 rule as the solid semi-solid orliquid residue generated during the treatment of domestic sewage in a treatmentworks The term biosolids is not used in the Part 503 rule but EPA (1995)defines biosolids as ldquothe primarily organic solid product yielded by municipalwastewater treatment processes that can be beneficially recycledrdquo as soilamendments Use of the term biosolids has been controversial because of theperception that it was created to improve the image of sewage sludge in apublic-relations campaign by the sewage industry (Rampton 1998) For thepurposes of this report the committee considers sewage sludge to be the solidsemi-solid or liquid residue generated during treatment of domestic sewageand biosolids to be sewage sludge that has been treated to meet the land-application standards in the Part 503 rule or any other equivalent land-application standards
It is estimated that approximately 56 million dry tons of sewage sludge areused or disposed of annually in the United States of which approximately 60are used for land-application or public distribution (see Chapter 2) On the basisof data from EPA (1999a) and USDA (1997) EPA estimates that approximately01 of available agricultural land in the United States is treated with biosolidsBiosolids are a complex mixture that may contain organic inorganic andbiological pollutants from the wastewaters of households commercialestablishments and industrial facilities and compounds added or formed duringvarious wastewater treatment processes Such pollutants include inorganiccontaminants (eg metals and trace elements) organic contaminants (egpolychlorinated biphenyls [PCBs] dioxins pharmaceuticals and surfactants)and pathogens (eg bacteria viruses and parasites) Sewage-sludge treatmentprocesses are intended to reduce the volume and organic content of biosolidsand to reduce the presence of pathogens but retain beneficial properties for soil-amendment and land-reclamation purposes Figure 1ndash1 provides a simplifiedschematic of how biosolids are produced and illustrates how the content ofbiosolids can vary depending on the wastewater streams and the variations intreatment processes See Figures 2ndash1 and 2ndash2 in
INTRODUCTION 18
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FIGURE 1ndash1 Biosolids production
aRequired by federal and state agenciesbPrior to dewatering sewage sludge is conditioned and thickened by addingchemicals (eg ferric chloride lime or polymers)
INTRODUCTION 19
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BOX 1ndash1 DEFINITIONS
Sewage sludge the solid semi-solid or liquid residue generatedduring the treatment of domestic sewage in a treatment works
Biosolids
bull EPArsquos definition the primarily organic solid product yielded bymunicipal wastewater treatment processes that can be beneficiallyrecycled (whether or not they are currently being recycled)
bull Committeersquos definition sewage sludge that has been treated to meetthe land-application standards in the Part 503 rule or any otherequivalent land-application standards or practices
Chapter 2 for more detailed diagrams of wastewater and sewage sludgetreatment
Biosolids are applied to agricultural and nonagricultural lands as soilamendments because they can improve the chemical and physical properties ofsoils and they contain nutrients and trace elements important for plant growthAgricultural lands include sites where food crops (for human or animalconsumption) and nonfood crops are grown Nonagricultural lands includeforests rangelands and public contact sites (eg public parks golf courses andcemeteries) Severely disturbed lands such as strip mines and gravel pits canbe reclaimed with biosolids
Biosolids are divided into two classes on the basis of pathogen contentClass A and Class B Class A biosolids are treated to reduce the presence ofpathogens to below detectable levels and can be used without any pathogen-related restrictions at the application site Class A biosolids can also be baggedand sold to the public if other requirements are met Class B biosolids aretreated to reduce pathogens but still contain detectable levels of them Class Bbiosolids have site restrictions that seek to minimize the potential for humanand animal exposure until environmental factors such as heat sunlight anddesiccation have reduced pathogens further Class B biosolids cannot be sold orgiven away in bags or other containers or used at sites with public use
Sewage sludge that is not treated to meet land-application standards isusually disposed of at landfills or surface disposal sites that contain only sewagesludge or is incinerated Regulations pertaining to these disposal practices arecontained in the Part 503 rule Review of disposal regulations is howeveroutside the scope of the committeersquos task
INTRODUCTION 20
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Pollutant Standards
Different methods were used to establish the chemical pollutant andpathogen standards in the Part 503 rule For the chemical pollutant limitssewage-sludge surveys (EPA 1982 1990) and risk assessments (EPA 1992ab)were used to identify and characterize risks from chemical pollutants in sewagesludge The risk assessments considered a variety of pathways by whichhumans animals plants and soil organisms could be exposed to biosolidpollutants Chemical standards (ie ceiling concentrations (mgkg) cumulativepollutant loading rates (kghectare) pollutant concentration limits (mgkg) andannual pollutant loading rates (kghectare365-day period) were originallyestablished for 10 inorganic chemicals using the most limiting exposurepathway These chemicals are arsenic cadmium chromium1 copper leadmercury molybdenum2 nickel selenium and zinc Standards for five of thecurrently regulated chemicals (arsenic cadmium lead mercury and selenium)are based on potential adverse human health effects Most standards are only foreight chemicals only a ceiling concentration is currently established formolybdenum as described in the footnote
In December 1999 EPA issued a proposal to amend the Part 503 rule forland-applied biosolids by adding a risk-based concentration limit for dioxins acategory of organic compounds that includes 29 specific congeners ofpolychlorinated dibenzo-p-dioxins polychlorinated dibenzofurans and coplanarpolychlorinated biphenyls (PCBs) (EPA 1999b) (More details about thisproposal are presented in Chapters 2 and 5)
EPA established operational standards for pathogens in biosolids ratherthan risk-based standards although it conducted a preliminary set of riskassessments for viruses (EPA 1992c) bacteria (EPA 1991a) and parasites (EPA1991b) The operational standards are pathogen-reduction requirements thegoal of which is to reduce the presence of pathogens (including
1Chromium was deleted from regulation in 1995 This amendment was the result of apetition filed in 1993 by the Leather Industries of America Inc to the US Circuit Courtof Appeals for the District of Columbia Circuit seeking review of the pollutant limits forchromium The court remanded the request to EPA for additional justification ormodification of its chromium regulations in the Part 503 rule The Agency subsequentlydetermined that there was ldquoan insufficient basis at this time for the regulation ofchromium in sewage sludge that is applied to landrdquo (EPA 1995)
2Standards for molybdenum were dropped from the original regulation Currentlyonly a ceiling-concentration limit is available for molybdenum and a decision aboutestablishing new pollutant limits for this metal has not been made
INTRODUCTION 21
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enteric viruses bacteria parasites and viable helminth ova) in biosolids tolevels that are unlikely to pose a threat to public health and the environmentunder specific use conditions Because of the variety of different pathogens thatmight be present in sewage sludge and the impracticality of testing for all ofthem EPA requires analyses of ldquoindicator organismsrdquo An indicator organism isa particular species of microorganism whose presence is used to indicate that acertain set of pathogenic organisms might also be present The Part 503 rulespecifies operational standards for fecal coliforms Salmonella sp bacteriaenteric viruses and viable helminth ova
Earlier NRC Review
In 1996 the NRC published the report Use of Reclaimed Water and Sludgein Food Crop Production which reviewed the practice of using wastewater andbiosolids for agricultural purposes That report focused specifically on issuesrelated to food-crop production and evaluated the regulations for chemicals andpathogens in the Part 503 rule reviewed the impacts on soil crops andgroundwater and considered the economic legal and institutional issues of thepractice The current report is different from the earlier one in that itencompasses all land-application uses (not only food-crop production) isfocused only on human health risks and provides an in-depth assessment of themethods used to assess those risks
The 1996 report concluded that ldquoWhile no disposal or reuse option canguarantee complete safety the use of [municipal wastewater and biosolids] inthe production of crops for human consumption when practiced in accordancewith existing federal guidelines and regulations presents negligible risk to theconsumer to crop production and to the environment Current technology toremove pollutants from wastewater coupled with existing regulations andguidelines governing the use of reclaimed wastewater and sludge in cropproduction are adequate to protect human health and the environmentrdquoHowever the report also highlighted limitations and inconsistencies in EPArsquosrisk evaluation and made recommendations for additional research Excerpts ofthe major recommendations of that report are presented in Box 1ndash2
One of the major concerns with respect to EPArsquos risk evaluation was thereliability of the National Sewage Sludge Survey (EPA 1990) which served asthe basis for many of the decisions made in the Part 503 rule including EPArsquosdecision to exempt organic pollutants from regulation Inconsistencies werefound in the surveyrsquos sampling and data-reporting methods that undermined thereliability of the data Therefore it was recommended that EPA conduct anothernational survey of pollutants in biosolids To date no comprehensive survey hasbeen performed
INTRODUCTION 22
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ibut
ion
BOX 1ndash2 RECOMMENDATIONS IN NRC (1996) REPORT
Adequacy of Existing Regulations for Pathogens in ReclaimedWater and Biosolids
bull Until a more sensitive method for the detection of Salmonella inbiosolids is developed the present test should be used for supportdocumentation but not be substituted for the fecal coliform test inevaluating biosolids as Class A
bull EPA should continue to develop and evaluate effective ways to monitorfor specific pathogens in biosolids
bull EPA should reevaluate the adequacy of the 30-day waiting periodfollowing the application of Class B biosolids to pastures used forgrazing animals
Adequacy of Existing Regulations for Harmful Chemicals inReclaimed Water and Biosolids
bull A more comprehensive and consistent survey of municipal wastewatertreatment plants is needed to show whether or not toxic organiccompounds are present in biosolids at concentrations too low to pose arisk to human and animal health and to the environment In conductinga second NSSS EPA should strive to improve the integrity of the databy using more consistent sampling and data-reporting methods TheEPA should not exclude chemicals from regulatory considerationbased solely on whether or not those chemicals have been bannedfrom manufacture in the United States (eg PCBs) since they are stillfound in sewage sludge from many wastewater treatment plants
Marketing Biosolids Products to the Public
bull The Part 503 rule should be amended to more fully assure that onlybiosolids of exceptional quality in terms of both pathogen andchemical limits are marketed to the general public so that furtherregulation and management beyond the point of sale or give-awaywould not be necessary
Soil Crop and Groundwater Effects
bull When determining biosolids and fertilizer application rates an analysisof the rates of organic nitrogen mineralization should be performed inorder to avoid buildup of excess nitrate-nitrogen Nitrate-nitrogen that isnot taken up by plants may contribute to excess fertilisation andleaching Where excess phosphorus is of concern soil phosphoruslevels should be monitored and biosolids application rates should beadjusted to correspond to crop phosphorus rather than nitrogen needs
bull As more croplands are treated with biosolids and reach their regulatorylimit of chemical pollutant loading from biosolids applications additionalinforma
INTRODUCTION 23
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bull tion will be needed to assess potential long-term impacts of biosolidson groundwater quality and on the sustainability of soils for cropproduction
Economic Legal and Institutional Issues
bull Any payment program designed to promote agricultural use of treatedeffluents or biosolids should be carefully structured to avoid thecreation of incentives to apply reclaimed water or biosolids at rates inexcess of agronomic rates and to avoid undermining farmmanagement practices needed to protect public and occupationalhealth and the environment
bull States and municipalities that wish to implement a beneficial-useprogram need to address public concerns and provide assurances thatthe new uses of biosolids and wastewater do not endanger health orthe environment in application areas The public and local officialsshould be involved in the decision-making process at an early stage
bull The operators of municipal wastewater treatment facilities and theparties using biosolids and wastewater should implement visiblestringent management and self-regulation measures includingmonitoring and reliable reporting by farmers and should supportvigilant enforcement of appropriate regulations by local or stateagencies Implementation of these measures will be credible means ofpreventing nuisance risks and harm to people property and highlyvalued nearby resources
bull The municipal utility should carry out demonstration programs for publiceducation and to verify the effectiveness of management and self-regulatory systems In addition the utility should be prepared toindemnify farmers against potential liabilities when farmersrsquo financingby banks or other lenders may hinge on this assurance
bull Management of biosolids for beneficial use should be more visiblylinked to existing regulations governing its disposal Program credibilitymay be improved and public concern reduced if federal state andmunicipal regulators clearly assign authority to local governments forresponding to any reports of adverse consequences related tobeneficial use of biosolids such as ground water contamination odorattraction of vermin or illnesses The public should be aware that stateand local units of government have the necessary regulatory authorityto take corrective actions against parties who have violated rules andguidance
INTRODUCTION 24
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t th
is P
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s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
The 1996 NRC report also examined the adequacy of EPArsquos pathogenrequirements and made recommendations to improve them (Box 1ndash2) EPA3
has indicated that it plans to develop better analytical protocols for detectingpathogens including Salmonella as resources permit It notes that in generalmost biosolids producers continue to demonstrate Class A quality by relying onthe fecal coliform tests rather than the Salmonella test EPA also plans todevelop monitoring protocols for specific pathogens
EPA3 has not decided whether to reevaluate the 30-day waiting periodrequired before grazing is allowed on biosolids-amended pastures A decisionwill be based on EPArsquos review of a workshop held in June 2001 titled EmergingPathogen Issues in Biosolids Animal Manures and Other Similar By-productsand a microbial risk-assessment model currently being developed byresearchers at the University of California at Berkeley for the WaterEnvironment Research Foundation
HUMAN HEALTH AND RISK-ASSESSMENT ISSUES
A number of potential human health and risk-assessment issues werebrought to the committeersquos attention Some of the major human health issuesinclude the following
bull Differences in the extent of health complaints There are severalallegations of deaths caused by exposure to biosolids and anecdotalreports of illnesses ranging from acute to chronic problems includingheadaches respiratory problems and gastrointestinal illnesses Mosthealth complaints appear to be concentrated in specific locales Otherlocales receive few or no complaints
bull Citizen complaints Odors from biosolids are the principal complaint fromcitizens living near biosolids land-application sites Citizens have alsocomplained of attraction of vectors (eg insects birds) declines inproperty values and damage to property and public roads by the heavytrucks used to transport biosolids These types of complaints havesometimes been categorized as nuisance problems or aesthetic issues butconcerns have been raised that odors and vector attraction could havehealth impacts
3Responses to follow-up questions from US House Science Committee Hearing onBiosolids March 22 2000 Submitted to the committee by Elizabeth MSokul OversightCounsel Committee on Science US House of Representatives
INTRODUCTION 25
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t th
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s ne
w d
igita
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ntat
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of t
he o
rigin
al w
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has
been
rec
ompo
sed
from
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L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
bull Differences in public confidence in enforcement and compliance with thePart 503 rule A variety of alleged incidents were brought to thecommitteersquos attention including improper application of biosolidsinadequate public-access restrictions at Class-B application sites andviolations of the 30-day waiting period before allowing grazing on treatedpastures It was beyond the scope of the committeersquos task to investigate orverify these allegations but an audit of the national biosolids program byEPArsquos Office of Inspector General concluded that ldquoEPA does not have aneffective program for ensuring compliance with the land applicationrequirements of Part 503 Accordingly while EPA promotes landapplication EPA cannot assure the public that current land applicationpractices are protective of human health and the environmentrdquo (EPA 2000)
In addition to health issues questions have been raised about the risk-assessment approaches used to establish the biosolids standards Major issuesinclude the following
bull Regional and site-specific considerations Biosolids content use practicesand application-site characteristic (eg geology and climate) vary greatlyamong and within regions It is important that these variations areconsidered in the risk assessment used to establish the biosolids standards
bull Difficulties in conducting risk assessments when the available database ispoor Major gaps in the biosolids data include need for updatedcharacterization of biosolids constituents exposure information andunderstanding of relevant health effects
bull Challenge of assessing risks from a complex mixture Biosolids are amixture of organic and inorganic chemicals and biological agents Risk-assessment procedures typically quantify risks from single chemicals andassume additivity when multiple chemicals are present Although muchthought has been given to evaluating risks from chemical mixturesstrategies for considering risks from exposure to complex mixtures arestill in development
THE COMMITTEErsquoS TASK
The Clean Water Act requires EPA to periodically reassess the scientificbasis of the Part 503 rule including the option of adding pollutants to theregulation Several advances and improvements in conducting risk assessmentshave occurred since the promulgation of the rule in 1993 Some researchershave questioned the scientific basis and data used in establishing EPArsquosbiosolids standards noting data gaps nonprotective policy choices and
INTRODUCTION 26
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is P
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s ne
w d
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of t
he o
rigin
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ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
more stringent standards set by other countries In addition there is increasingconcern among communities near land-application sites about the health risksfrom exposure to biosolids For these reasons EPA asked the NRC to conductan independent evaluation of the technical basis of the Part 503 rule land-application standards
In response to this request the NRC convened the multidisciplinaryCommittee on Toxicants and Pathogens in Biosolids Applied to Land Thecommittee was asked to review information on the land application of biosolidsand to evaluate the methods used by EPA to assess human health risks fromchemical pollutants and pathogens in biosolids Specifically the committee wasasked to
1 Review the risk-assessment methods and data used to establishconcentration limits for chemical pollutants in biosolids todetermine whether they are the most appropriate approachesConsider the NRCrsquos previous (1996) review and determine whetherthat reportrsquos recommendations have been appropriately addressedConsider (a) how the relevant chemical pollutants were identified(b) whether all relevant exposure pathways were identified (c)whether exposure analyses particularly from indirect exposuresare realistic (d) whether the default assumptions used in the riskassessments are appropriate and (e) whether the calculations usedto set pollutant limits are appropriate
2 Review the current standards for pathogen elimination in biosolidsand their adequacy for protecting public health Consider (a)whether all appropriate pathogens were considered in establishingthe standards (b) whether enough information on infectious doseand environmental persistence exists to support current controlapproaches for pathogens (c) risks from exposure to pathogensfound in biosolids and (d) new approaches for assessing risks tohuman health from pathogens in biosolids
3 Explore whether approaches for conducting pathogen riskassessment can be integrated with those for chemical riskassessment If appropriate recommend approaches for integratingpathogen and chemical risk assessments
THE COMMITTEErsquoS APPROACH
To accomplish its task the committee held five meetings between March2001 and May 2002 The first two meetings involved data-gathering sessionsthat were open to the public The committee heard from EPA the NationalInstitute for Occupational Safety and Health industry representativesenvironmental and community groups and academics Many concerned members
INTRODUCTION 27
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he o
rigin
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ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
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the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
of the public attended the meetings and were given the opportunity to addressthe committee Citizens living near land-application sites voiced concerns aboutodors health effects lack of investigation into health complaints andapplication practices that do not comply with the regulations At its secondmeeting the committee also visited an agricultural field in Riverside CountyCalifornia where Class B biosolids were being applied The purpose of the visitwas to observe techniques used to apply biosolids to an agricultural field Thecommittee also reviewed a large body of written material on biosolids Thecommittee relied on peer-reviewed publications as its primary source ofinformation but unpublished data (submitted by various sources includingindustry representatives and the public) were sometimes used to supplementexisting information or when no other information was available
The committee is aware that some readers expect this report to cover allaspects of biosolids use and determine whether EPA should continue topromote its use That expectation goes well beyond the committeersquos chargeTherefore it is important to clarify what this report addresses and what it doesnot address
This report focuses on the land application of Class A and Class Bbiosolids It does not consider risks from sewage treatment processes (includingcomposting) storage or transporting nor does it cover risks from disposalpractices of landfilling surface disposal or incineration
The committee was asked to devote its efforts to evaluating existingbiosolids regulations (as of July 1 2000) in 40 CFR Part 503 Because theregulations cover only chemical (specifically inorganics) and pathogenicpollutants radioactive contaminants were not included in the committeersquosassessment even though the committee is aware that radioactive compoundsmay be present in biosolids The committeersquos assessment also excluded an in-depth evaluation of EPArsquos risk assessment and proposed regulations fordioxins because they were not finalized at the time of writing However thecommittee did evaluate the scientific basis of EPArsquos original decision not toregulate organic pollutants in biosolids
Although the Part 503 rule considers risks to both human andenvironmental health the committee was asked to focus its evaluation onhuman health risks and not on plant animal or ecological risks The committeeinterpreted this task to include an evaluation of relevant occupational health inaddition to public health It is also important to emphasize that the primarypurpose of this report is to provide an evaluation of the risk-assessment methodsand approaches used to establish the biosolids land-application standards and isnot an investigation into the validity of allegations of biosolids-related illnessesRisk assessment is the characterization of potential adverse health effectsresulting from exposure to environmental hazards It is a process
INTRODUCTION 28
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ompo
sed
from
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L fil
es c
reat
ed f
rom
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orig
inal
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er b
ook
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fro
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heor
igin
al ty
pese
tting
file
s P
age
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ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
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erro
rs m
ay h
ave
been
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iden
tally
inse
rted
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ase
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t ver
sion
of t
his
publ
icat
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as th
e au
thor
itativ
e ve
rsio
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r attr
ibut
ion
separate from risk management which is the term used to describe the processby which risk-assessment results are integrated with other information (egsocial economic and engineering factors) to make decisions about thenecessity method and extent of risk reduction
REPORT ORGANIZATION
The remainder of this report is organized into six chapters Chapter 2describes the history of the biosolids regulations treatment processes usepractices compliance issues and risk-management practices in the UnitedStates It also provides a brief overview of biosolids regulations and practices inEurope Chapter 3 reviews the available evidence on human health effects fromexposure to biosolids Chapter 4 presents developments in risk assessment sincethe Part 503 rule was established and discusses current risk-assessmentpractices used by EPA Chapter 5 reviews EPArsquos risk-assessment approach tosetting limits for chemical pollutants in biosolids EPArsquos pathogen-reductionstandards are reviewed in Chapter 6 along with new developments in the areaof risk assessment for microbial agents Chapter 7 explores whether it ispossible to use an integrated approach to assess the risks from a complexmixture of chemical and biological agents
REFERENCES
EPA (US Environmental Protection Agency) 1982 Fate of Priority Pollutants in Publicly OwnedTreatment Works Vol 1 Final Report EPA4401ndash82303 Effluent Guidelines DivisionWater and Waste Management US Environmental Protection Agency Washington DCSeptember 1982
EPA (US Environmental Protection Agency) 1990 National Sewage Sludge Survey availabilityof information and data and anticipated impacts on proposed regulations Proposed ruleFed Regist 55(218)47210ndash47283 (November 9 1990)
EPA (US Environmental Protection Agency) 1991a Preliminary Risk Assessment for Bacteria inMunicipal Sewage Sludge Applied to Land EPA6006ndash91006 Office of Research andDevelopment US Environmental Protection Agency Washington DC July 1991
EPA (US Environmental Protection Agency) 1991b Preliminary Risk Assessment for Parasites inMunicipal Sewage Sludge Applied to Land EPA6006ndash91001 Office of Research andDevelopment US Environmental Protection Agency Washington DC March 1991
EPA (US Environmental Protection Agency) 1992a Technical Support Document for LandApplication of Sewage Sludge Vol 1 EPA 822R-93ndash001a Office of
INTRODUCTION 29
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he o
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ork
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ompo
sed
from
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L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
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prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Water US Environmental Protection Agency Washington DC November 1992EPA (US Environmental Protection Agency) 1992b Technical Support Document for Land
Application of Sewage Sludge Vol 2 Appendices EPA 822R-93ndash001b Office of WaterUS Environmental Protection Agency Washington DC November 1992
EPA (US Environmental Protection Agency) 1992c Preliminary Risk Assessment for Viruses inMunicipal Sewage Sludge Applied to Land EPA600R-92064 Office of Research andDevelopment US Environmental Protection Agency Washington DC June 1992
EPA (US Environmental Protection Agency) 1993 Federal Register February 19 1993 40 CFRParts 257 403 and 503 The Standards for the Use or Disposal of Sewage Sludge FinalRules EPA 822Z-93001 US Environmental Protection Agency Washington DC
EPA (US Environmental Protection Agency) 1995 A Guide to the Biosolids Risk Assessmentsfor the EPA Part 503 Rule EPA832-B-93ndash005 Office of Wastewater Management USEnvironmental Protection Agency Washington DC September 1995 [Online] Availablehttpwwwepagovowmbio503ruleindexhtm [December 20 2001]
EPA (US Environmental Protection Agency) 1999a Biosolids Generation Use and Disposal inthe United States EPA530-R-99ndash009 Office of Solid Waste and Emergency ResponseUS Environmental Protection Agency Washington DC September 1999 [Online]Available httpwwwepagovepaoswernonhwcompostbiosolidpdf [March 19 2002]
EPA (US Environmental Protection Agency) 1999b Standards for the use or disposal of sewagesludge Proposed rule Fed Regist 64(246)72045ndash72062 (December 23 1999)
EPA (US Environmental Protection Agency) 2000 Water Biosolids Management andEnforcement Audit Report No 2000-P-10 Office of Inspector General March 20 2000[Online] Available httpwwwepagovoigearthauditlist30000P0010pdf [December20 2001]
NRC (National Research Council) 1996 Use of Reclaimed Water and Sludge in Food CropProduction Washington DC National Academy Press
Rampton S 1998 Let them eat nutri-cake Merriam-Webster thinks our ldquobiosolidsrdquo donrsquot stink(how the word biosolid became a dictionary term) Harperrsquos Magazine (November 1998)
USDA (US Department of Agriculture) 1997 1997 Census of Agriculture Vol 1 National Stateand Country Tables USDA National Agricultural Statistics Service [Online] Availablehttpwwwnassusdagovcensus [April 16 2002]
INTRODUCTION 30
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from
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fro
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tting
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ther
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ed a
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ibut
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2
Biosolids Management
Wastewater treatment necessarily produces two end products effluent andsewage sludge All wastewater generated in homes businesses industries andother venues that is conveyed to wastewater treatment plants is treated to alloweffluent discharge back into the surface and groundwaters of the United StatesSewage sludge is likewise treated in the wastewater process generally throughaerobic or anaerobic microbial activity for specified time periods andtemperatures Both effluent and sewage sludge require treatment to ensure thattheir release into the environment is protective of human health and theenvironment as required by the Clean Water Act (CWA) Sewage sludge isdefined as the solid semi-solid or liquid residue generated during the treatmentof domestic sewage in a treatment works and biosolids are defined in thisreport as sewage sludge that has been treated to meet standards for landapplication under Part 503 of the CWA or any other equivalent land-applicationstandards
Of the nationrsquos estimated 263 million people in 1996 190 million of themor 72 contributed wastewater directly through a sewerage system toapproximately 16000 publicly owned treatment works (POTW) (EPA 2000a)The remaining 73 million people discharged wastewater to some form of on-sitetreatment system or holding tank more than half of which also is ultimatelydischarged to a POTW (Razvi 2000) Each person discharging human waste toa wastewater treatment system produces approximately 47 dry pounds (21kilograms) of sewage sludge each year (EPA 1993) As the population of the
BIOSOLIDS MANAGEMENT 31
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ompo
sed
from
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inal
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fro
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igin
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tting
file
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e le
ngth
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ord
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ther
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ng-s
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rmat
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not b
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ed a
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typo
grap
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erro
rs m
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his
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e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
United States increases the percentage of the population directly discharging toPOTWs is projected to increase to 88 by 2016 (EPA 2000a) The ability toeffectively treat and return wastewater and sewage sludge to the environment ina protective manner is of paramount importance from both a public-health andan environmental perspective In partial recognition of this fact Congresspassed the CWA of 1972 and the federal government has contributed $611billion in grants and $161 billion in low-interest loans to municipal and localgovernments between 1972 and 1999 for capital construction costs to providenecessary support for wastewater and sewage-sludge treatment and dispositionof biosolids (EPA 2000a) Approximately 40 of that amount has been used forsewage sludge treatment and disposition of biosolids (Peavy et al 1985)Sewage sludge is generated in several treatment processes that generally includeprimary (from primary clarification) and secondary (from secondaryclarification) sewage sludge The general process of treating wastewater andsewage sludge is illustrated in Figures 2ndash1 and 2ndash2
EPA is responsible under Section 405 of the CWA to promulgateregulations for sewage sludge use or disposal The CWA Amendments of 1987added special provisions that required EPA to identify toxic pollutants and setsewage-sludge standards that are ldquoadequate to protect public health and theenvironment from any reasonably anticipated adverse effect of each pollutantrdquo(emphasis added) Recognizing that sewage-sludge production will continue toincrease and that sewage sludge possesses many potential beneficial propertiesfor agricultural production federal and state agencies have long advocated therecycling of it as biosolids through land application (EPA 1981 1984 1991)The other primary options for sewage sludge disposition are to bury it in alandfill or to incinerate it Although these latter options possess inherent risksand environmental difficulties these options are beyond the scope of this report(see Chapter 1)
Of the 16000 POTWs in the United States approximately 8650 generatesewage sludge that must be used or disposed of at least annually (WisconsinDepartment of Natural Resources unpublished data 2001) Based on data from37 states approximately 5900 of these sewage sludge generators (68) eitherland apply or publicly distribute over 34 million dry tons of biosolids each year(see also End Use Practice section of this chapter) Most of this recycling use isconducted without public opposition and with no documented adverse healtheffects However recent allegations of adverse health effects have receivedmedia and congressional attention Chapter 3 assesses the epidemiologicalevidence and approach for health effects associated with biosolids productionand application but does not systematically investigate these allegationsRather the report examines the process by which the regulations wereestablished and determines whether advances in risk-assessment methodswarrant a revisiting of the process
BIOSOLIDS MANAGEMENT 32
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ompo
sed
from
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L fil
es c
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rom
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fro
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igin
al ty
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tting
file
s P
age
brea
ks a
re tr
ue to
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orig
inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
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ever
can
not b
ere
tain
ed a
nd s
ome
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grap
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erro
rs m
ay h
ave
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iden
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rted
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n fo
r attr
ibut
ion
FIG
UR
E 2
ndash1 T
he p
roce
ss s
chem
atic
del
inea
ting
wat
er a
nd w
aste
wat
er tr
eatm
ent a
long
wit
h th
e se
wag
e sl
udge
str
eam
BIOSOLIDS MANAGEMENT 33
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t th
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of t
he o
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ompo
sed
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rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
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inal
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FIG
UR
E 2
ndash2 S
ewag
e sl
udge
trea
tmen
t alt
erna
tive
s
BIOSOLIDS MANAGEMENT 34
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This chapter briefly examines the development of the Part 503 rule certainrelated issues and what EPA has done to implement the rule sincepromulgation It also reviews how states implement the rule whether or notthey have explicit delegated authority from EPA An examination of biosolidsregulations and practices in Europe is then used to compare and contrast thesepractices An overview of the acceptable pathogen treatment controls and landapplication site restrictions is presented as well as associated methods forstabilization to reduce the attraction to vectors such as rodents Issues are raisedthat relate to the verification of the efficacy of treatment Finally this chapterexamines end-use practices in the United States biosolids quality achieved dataon nonregulated pollutants risk-management practices inherent to landapplication of biosolids (primarily Class B) and to the risk-assessment processand compliance and enforcement strategies and action taken by EPA or states
FEDERAL BIOSOLIDS REGULATIONS AND CURRENTSTATE OF PROGRAM
History
The current biosolids standards became effective in Part 503 of Chapter 40of the Code of Federal Regulations (40 CFR 503) on March 22 1993 (EPA1993) More specifically the regulations are established as GeneralRequirements Pollutant Limits Management Practices Operational StandardsFrequency of Monitoring Requirements Record Keeping and Reporting Therequirements apply to each of the three major methods of ultimate disposition ofsewage sludge or biosolids recycling and public distribution burial in amunicipal solid-waste landfill or a surface disposal site or incinerationEnforceable standards are established for all three options but this reportfocuses only on land application and public distribution The standards weredeveloped over more than 10 years and received both public and private inputFrom September 13 1979 until 40 CFR 503 was published standards for theland application of biosolids were set in 40 CFR Part 257 (EPA 1979) Researchfocusing on the beneficial micro- and macronutrients present in treated sewagesludge had been conducted at numerous universities before the publication ofthe 1979 regulations (eg Keeney et al 1975) Indeed Wisconsin statutesspecifically encouraged the responsible recycling of biosolids through use onagricultural land beginning in 1973 (Wisconsin Statutes Assembly Bill 1281973)
BIOSOLIDS MANAGEMENT 35
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Because POTWs typically have industrial contributors to their wastewatercollection systems wastewater pretreatment regulations became effectivethrough 40 CFR Part 403 on June 26 1978 with a stated objective to
a prevent the introduction of pollutants into POTWs which willinterfere with the operation of a POTW including interference withits use or disposal of municipal biosolids
b prevent the introduction of pollutants into POTWs which will pass through the treatment works or otherwise be incompatible withsuch works and
c improve opportunities to recycle and reclaim municipal andindustrial wastewaters and biosolids (EPA 1999a)
These regulations to control pollution dramatically reduced theconcentrations of selected pollutants discharged to applicable sewerage systemsand therefore also the concentrations in the resultant biosolids (see alsoCharacterization of Biosolids section)
Federal Policy
EPA has had a long-standing policy of promoting the beneficial use ofbiosolids and a regulatory mandate to review and revise related regulationsperiodically as new research warrants In January 1981 EPA published astatement of federal policy and guidance with the US Food and DrugAdministration (FDA) and the US Department of Agriculture (USDA) for theproper management and necessary controls of land application of biosolids forthe production of fruits and vegetables EPA (1984) further formalized itspolicy of promoting beneficial use and developing a comprehensive regulatoryapproach as mandated by the CWA in the Federal Register on June 12 1984EPA again clarified that position through the publication of an interagencypolicy which with six other federal agencies promoted the beneficial use ofbiosolids in the Federal Register on July 18 1991 (EPA 1991)
Section 402 of the CWA sets provisions for permitting dischargesincluding sewage sludge to waters of the United States As authorized by theCWA the National Pollutant Discharge Elimination System (NPDES) permitprogram has been in place since 1972 and regulates point sources of waterpollution such as pollutants discharged from pipes or ditches Many statesconsider the land application of biosolids to be a point-source discharge togroundwater and regulate this practice under the permit program Individualhomes that are connected to a municipal system use a septic system or do not
BIOSOLIDS MANAGEMENT 36
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have a surface discharge do not need an NPDES permit however industrialmunicipal and other facilities must obtain permits if their discharges go directlyto surface waters In most cases the NPDES permit program is administered byauthorized states Chapter 40 of CFR 501 was published in 1989 to set aregulatory framework for states seeking delegated authority to implement abiosolids program under permits in compliance with Section 402 At presentthere are five states that have received delegation (Oklahoma Utah TexasWisconsin and South Dakota) and about 20 that are seeking such authorityConversely 44 states have received delegated implementation authority for theNPDES effluent permit program (EPA 1999a) Notably delegation for theeffluent permit program is funded and delegation for and implementation of thebiosolids program is not
Proposed Regulation
40 CFR 503 was published for public comments on February 6 1989EPArsquos original risk assessment (see Chapter 5 for further information) definedthe at-risk population as the most exposed individual (MEI) The MEI is aperson who is maximally exposed to a pollutant in biosolids for a lifetime EPAconducted an aggregate public-health risk assessment that estimated the riskfrom land application of biosolids in the absence of any regulation Thataggregate assessment found that the risk would be less than one cancer case peryear and that approximately 1000 persons would exceed a threshold leadconcentration and 500 would experience some lead-related health effects Withthe final regulation in place the resultant risk was predicted to be less than onecancer case less than one person exceeding a threshold blood lead level andless than one person experiencing adverse lead effects (EPA 1993) In additionthis risk would present itself only at such time as all assumptions in the riskassessment were fulfilled
The Cooperative State Research Service Technical Committee W-170composed of university researchers organized a Peer Review Committee (PRC)from academia EPA environmental groups and units of state and localgovernment to provide expert and extensive comments to EPA on the proposedrule (Cooperative State Research Service Technical Committee W-170 1989)Two critical points were raised during the public comment period by the PRC(1) The MEI was modeled with multiple layers of conservative exposures thatcould not exist in reality and this contradicted the notion of reasonablyanticipated adverse effects and (2) the research for metal uptake was based onmetal salts and pot studies in greenhouses rather than field research They alsorecommended a risk-based approach to pathogens Al
BIOSOLIDS MANAGEMENT 37
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though EPA had an official policy to promote beneficial use of biosolids theproposed regulation would have substantially curtailed such use thusencouraging increased surface disposal and incineration
As a result of this extensive peer review EPA initiated additional researchand substantially modified the risk assessment and ultimately the regulationFor example EPA decided to use a highly exposed individual (HEI) rather thanan MEI in the risk assessment The HEI is a person who remains for anextended period at or adjacent to the site where maximum exposure occurs TheHEI represented a more reasonable case of exposure and still provided multiplesafety factors of protection (EPA 1993 1995a)
Final Regulations
There are three major categories of requirements establishing biosolidsquality and site-management criteria for land application Each of thesecategories is further divided into two sections When biosolids meet the strictestsection in all three categories it is considered exceptional quality (EQ)Management-practice requirements establish site restrictions and limitapplication rates on agricultural land for the remaining non-EQ biosolids Thethree requirement categories that establish biosolids quality are as follow
bull Pollutant concentrations versus ceiling concentrationsbull Class A pathogen criteria versus Class B pathogen criteria that include
management practicesbull Process-control criteria to reduce attraction to vectors versus physical
barriers from vectors
Biosolids that meet the requirements to be deemed EQ can be publiclydistributed without further regulation under 40 CFR 503 (If biosolids do notmeet the pollutant concentration limits and the other requirements they can stillbe publicly distributed as long as an information sheet is included that specifiesa maximum annual application rate) It is further stipulated that biosolids mustbe land applied at an ldquoagronomic raterdquo to not exceed the nitrogen requirementsfor the crop grown This stipulation is to avoid loss from the root zone to thegroundwater and to avoid excessive nitrogen buildup that may ultimately runoff to surface water
The Part 503 federal regulations for pathogen and vector attraction controlare and have been technologically based instead of risk based That is in partdue to unreliable pathogen assays and insufficient and variable data with respectto the fate and transport of pathogens in the natural environment (see Chapter 6for more details)
BIOSOLIDS MANAGEMENT 38
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Pollutant Concentrations
Specific pollutant concentrations were derived for nine metals (EPA1995a) The risk assessment examined 14 pathways of exposure and amaximum cumulative loading rate was determined for the most limitingpathway for each pollutant These values are shown in column 2 of Table 2ndash1
Assumptions were then made that a site was used for 100 consecutiveyears at a loading rate of 10 MThectare per year Next a back calculation wasused to determine a maximum concentration in the biosolids that would notallow the maximum cumulative loading rate to be attained The pollutantconcentration limits are intended to define biosolids that can be land appliedwithout requiring the applier to track cumulative pollutant loadings Themethods used by EPA to identify the pollutant concentration limits aredescribed in Chapter 5 That concentration became the pollutant concentrationlimit in all but two cases (see below) The current pollutant concentration limitsare shown in column 3 of Table 2ndash1
A National Sewage Sludge Survey (NSSS) was conducted by EPA (1990)for the purpose of gathering needed data on sewage sludge quality in the nationThe ceiling limit was set at the 99th percentile level found in the NSSS or therisk-based number whichever was greater The current ceiling limitconcentrations are shown in column 1 of Table 2ndash1 The risk-derived numberbecame the ceiling limit only for chromium (which was later deleted fromregulation see discussion later in this chapter) selenium and nickel1 In thosecases the 99th percentile value became the pollutant concentration limitCurrently both the ceiling concentration and pollutant concentration limits arerisk based for nickel and selenium
Thus land-applied biosolids that contain chemical concentrations less thanthose shown in column 3 of Table 2ndash1 do not need to track cumulative loadingsto sites because it is assumed that loadings will never approach the limitsshown in column 2 If land-applied biosolids have any chemical concentrationsbetween the values of column 3 and column 1 then cumulative loading recordsmust be kept for any such bulk application
It is important to note that when biosolids are sold or given away in a bagor container that weighs less than 1 MT it must meet the strictest standards forpathogen and vector control but does not need to meet the pollutantconcentration limits shown in column 3 of Table 2ndash1 As noted previously if itdoes not meet the column 3 limits an information sheet must be supplied
1The risk-based number and 99th percentile level found in the NSSS were the samefor nickel
BIOSOLIDS MANAGEMENT 39
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TA
BL
E 2
ndash1 P
ollu
tant
Con
cent
rati
on L
imit
s an
d L
oadi
ng R
ates
for
Lan
d A
ppli
cati
on in
the
Uni
ted
Sta
tes
Pol
luta
nt(1
) C
eili
ng C
once
ntra
tion
Lim
it (
mg
kg)a
(2)
Cum
ulat
ive
Loa
ding
Rat
e L
imit
(kg
ha)
a(3
) P
ollu
tant
Con
cent
rati
onL
imit
(m
gkg
)a(4
) A
nnua
l Pol
luta
ntL
oadi
ng R
ate
for
Dis
trib
uted
Bio
soli
dsE
xcee
ding
Col
umn
3 (k
gha
y)a
Ars
enic
7541
412
0C
adm
ium
8539
391
9C
oppe
r4
300
150
01
500
75L
ead
840
300
300
15M
ercu
ry57
1717
085
Mol
ybde
num
75-
--
Nic
kel
420
420
420
21S
elen
ium
100
100
100
5Z
inc
750
02
800
280
014
0A
ppli
es to
A
ll b
ioso
lids
that
are
land
appl
ied
Bul
k bi
osol
ids
Bul
k or
bag
gedb
bios
olid
sB
agge
db bi
osol
ids
whe
reat
leas
t one
ele
men
t doe
sno
t mee
t col
umn
3a D
ry w
eigh
t bas
is
b Bag
ged
bios
olid
s ar
e so
ld o
r gi
ven
away
in a
bag
or
cont
aine
r con
tain
ing
less
than
1 m
etri
c to
n (M
T)
Abb
revi
atio
ns m
g m
illi
gram
kg
kil
ogra
m h
a h
ecta
re y
yea
rSo
urce
Ada
pted
fro
m 4
0 C
FR P
art 5
03
BIOSOLIDS MANAGEMENT 40
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or instructions printed on the bag that prescribe loading rates that will notexceed annual loading rates shown in column 4 Because of the perceivedinfrequent use of this exception and the difficulty with tracking its use thecommittee concluded that it would be simpler to require that all biosolids soldor given away be EQ
Pathogen Control
Biosolids are divided into Class A and Class B on this basis of theirpathogen content and control Class A biosolids must undergo more extensivetreatment than Class B biosolids (described below) to reduce pathogensincluding bacteria enteric viruses and viable helminth ova to below detectableamounts Once these goals are achieved Class A biosolids can be land appliedwithout any pathogen-related restrictions at the site Biosolids having the leastfurther restrictions on land application are those meeting the Class A pathogenrequirements the vector control requirements and the high-quality pollutantconcentration limits for metals If all these requirements are met the biosolidscan be used with no more restrictions than any other fertilizer or soil-amendment product
The Class B pathogen requirements were developed from the 1979 40 CFR257 regulations for processes to significantly reduce pathogens (PSRP) In theinitial development of those requirements a PSRP was defined as a process thatreduces pathogenic viruses Salmonella bacteria and indicator bacteria (fecalcoliform) by at least 1 log (90) (EPA 1989)
The Class B biosolids requirements are intended to ensure that pathogensin biosolids have been reduced to amounts that are protective of public healthand the environment under the specific use conditions As a central element ofthe Class B criteria site restrictions designed to minimize potential for humanand animal contact apply until environmental factors have further reducedpathogens to low amounts Thus packaged Class B biosolids cannot be sold orgiven away for land application at public-contact sites lawns and homegardens but can be used in bulk quantities at appropriate types of land-application sites such as agricultural lands forests and mine reclamation sitesprovided the biosolids meet limits on pollutants vector-attraction reduction andother management requirements of Part 503 (EPA 1993) In addition biosolidscan be used as municipal-solid-waste (MSW) landfill cover in compliance with40 CFR Part 258
BIOSOLIDS MANAGEMENT 41
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Class A Pathogen Requirements
The Class A pathogen criteria require that both treatment-process controlrequirements and prescribed densities of either fecal coliform or Salmonella aresatisfied Pathogen criteria must be met at the same time or before the vector-attraction reduction requirements are met One of the following organismdensity requirements listed below must be satisfied for all Class A alternatives
Fecal Coliform Density Requirements The fecal coliform density mustbe less than 1000 most probable number (MPN) per gram (g) of total solids(TS) and that must be satisfied immediately after the treatment process iscompleted If the material is bagged or distributed at that time no retesting isrequired If the material is bagged distributed or land applied at a later time itmust be retested and the density requirement satisfied to ensure that regrowth ofbacteria has not occurred
Salmonella Density Requirements The Salmonella density must be lessthan 3 MPN per 4 g of TS and that must be satisfied immediately after thetreatment process is completed If the material is bagged or distributed at thattime no retesting is required If the material is bagged distributed or landapplied at a later time it must be retested and the density requirement satisfiedto ensure that regrowth of bacteria has not occurred
In addition one of the following treatment processes listed must be met tobe designated Class A biosolids (EPA 1999b) The goal of these processes is toreduce pathogen densities below specified detection limits for three types oforganisms Salmonella sp (lt3 MPN per 4g TS) enteric viruses (lt1 plaqueforming unit [PFU] per 4 g TS) and helminths (lt1 viable organism per 4 g TS)
Alternative 1mdashTemperature and Time Process These criteria werebased on a time-temperature relationship related to pasteurization studies and tocomposting data This alternative has been and is still used for aerobic digestionand anaerobic digestion An increased sewage-sludge temperature must bemaintained for a prescribed period according to the guidelines summarized inTable 2ndash2
Alternative 2mdashAlkaline Treatment Process The pH of the sewagesludge must be raised to greater than 12 for at least 72 hours (h) During thistime the temperature of the sewage sludge must be greater than 52degC for atleast 12 h In addition after the 72-h period the sewage sludge must be air driedto at least 50 TS
Alternative 3mdashPrior Test for Enteric Virus and Viable Helminth OvaThe sewage sludge must be analyzed for the presence of enteric viruses
BIOSOLIDS MANAGEMENT 42
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orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TABLE 2ndash2 Guidelines for Temperature Treatments
Total Solids Temperature Time EquationD=Time inDays t=Tempin degC
Notes
`7 `50degC `20min No heating ofsmall particlesby warmedgases orimmiscibleliquid
`7 `50degC `15s Small particlesheated bywarmed gasesor immiscibleliquid
lt7 gt50degC `15s to lt30min
lt7 `50degC `30min
and viable helminth ova If the sewage sludge is analyzed before pathogen-reduction processing and found to have densities of enteric virus of less than 1plaque-forming unit (PFU) per 4 g of TS and viable helminth ova of less than 1per 4 g of TS the sewage sludge is considered Class A biosolids with respect toenteric virus and viable helminth ova until the next monitoring event If thesewage sludge is analyzed before pathogen-reduction processing and found tohave densities of enteric virus greater than or equal to 1 PFU4 g of TS or viablehelminth ova of more than 1 per 4 g of TS and is tested again after processingand found to have densities of enteric virus of less than 1 PFU4 g of TS andviable helminth ova less than 1 per 4 g of TS the sewage sludge is consideredClass A biosolids when the treatment process is operated under the sameconditions that successfully reduced enteric virus and helminth ovaNote Temperatures calculated using the appropriate equation must never be less than 50degC Thetime values are not used in the calculations but are provided to indicate the prescribed duration thattemperature must be maintainedSource EPA 1999b
Alternative 4mdashPost-Test for Enteric Virus and Viable Helminth OvaProcess If the sewage sludge is not analyzed before pathogen-reductionprocessing for enteric viruses and viable helminth ova the sewage-sludgedensity of enteric viruses must be less than 1 PFU4 g of TS and the density ofviable helminth ova must be less than 1 per 4 g of TS at the time the sew
BIOSOLIDS MANAGEMENT 43
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
age sludge is used disposed of or prepared for sale or giveaway in a bag orcontainer or when the biosolids meets EQ requirements
Alternative 5mdashProcesses to Further Reduce Pathogens (PFRP)Alternative 5amdashComposting Process Compost the sewage sludge using
either within-vessel or static-aerated-pile composting methods and maintain thetemperature of the sewage sludge at 55degC or higher for 3 days or compost thesewage sludge using windrow composting methods and maintain thetemperature of the sewage sludge at 55degC or higher for 15 days or longerDuring this period a minimum of five windrow turnings are required
Alternative 5bmdashHeat Drying Process Dry the sewage sludge by director indirect contact with hot gases to reduce the moisture content of the sewagesludge to 10 or lower Either the temperature of the sewage-sludge particlesmust exceed 80degC or the wet bulb temperature of the gas in contact with thesewage sludge leaving the dryer must exceed 80degC
Alternative 5cmdashHeat Treatment Process Heat liquid sewage sludge toa temperature of 180degC or higher for 30 min
Alternative 5dmdashThermophilic Aerobic Digestion Process Agitateliquid sewage sludge with air or oxygen to maintain aerobic conditions Themean cell residence time for the sewage sludge must be 10 days at 55degC to 60degC
Alternative 5emdashBeta Ray Irradiation Process Irradiate the sewagesludge with beta rays from an accelerator at a dose of at least 10 megarad atroom temperature
Alternative 5fmdashGamma Ray Irradiation Process Irradiate the sewagesludge with gamma rays from certain isotopes such as cobalt 60 and cesium137 at a dose of at least 10 megarad at room temperature
Alternative 5gmdashPasteurization Process Maintain the temperature of thesewage sludge at 70degC or higher for 30 min or longer
Alternative 6mdashProcess Equivalent to Process to Further Reduce Pathogens (PFRP) Treat the sewage sludge in a process that is equivalent toPFRP as approved by the permit authority To obtain a Class A biosolid ratingthe process must reduce Salmonella species or fecal coliforms to below Class Acriteria and must operate under the specified conditions used in its applicationdemonstration to the EPA Pathogen Equivalency Committee (see below)
Class B Pathogen Requirements
In addition to management-practice requirements including site restric
BIOSOLIDS MANAGEMENT 44
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t th
is P
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file
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s ne
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igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
tions the Class B pathogen control requirements mandate that one of thefollowing be satisfied before land application
Fecal Coliform Limitation Compliance with the fecal coliform limitationfor Class B biosolids must be demonstrated by calculating the geometric meanof at least seven separate samples (TS analysis must be done on each sample)The geometric mean must be less than 2000000 MPN or colony-forming units(CFU) per g of TS
Aerobic Digestion Agitate the sewage sludge with air or oxygen tomaintain an aerobic condition for a mean cell residence time and temperaturebetween 40 days at 20degC and 60 days at 15degC (This process cannot be satisfiedduring the winter in most of the northern United States without additionalmeasures being taken to maintain adequate temperatures)
Anaerobic Digestion Treat the sewage sludge in the absence of air for aspecific mean cell residence time at a specific temperature Values for the meancell residence time and temperature must be between 15 days at 35degC to 55degCand 60 days at 20degC Straight-line interpolation to calculate mean cell residencetime is allowable when the temperature is between 35degC and 20degC
Lime Stabilization Add sufficient lime to the sewage sludge to raise thepH to 12 after 2 h of contact
Air Drying Dry the sewage sludge on sand beds or in paved or unpavedbasins for a minimum of 3 months During 2 of the 3 months the ambientaverage daily temperature must be above 0degC
Composting Compost the sewage sludge using either within-vessel static-aerated-pile or windrow composting methods and raise the temperature of thesewage sludge to 40degC or higher for 5 days For 4 h at some point during eachof the 5 days the temperature in the compost pile must exceed 55degC
Process Equivalent to Process to Significantly Reduce Pathogens (PSRP) Treat the sewage sludge in a process that is equivalent to a PSRP asapproved by the permit authority
Over the past 15 years two processes have been approved as PSRPequivalents by the EPA Pathogen Equivalency Committee (PEC) These are theN-Viro alkaline stabilization process and the Synox OxyOzone process Bothprocesses have been upgraded to PFRP status in more recent studiesSpecifically the N-Viro process meets the Class B equivalency criteria foralkaline stabilization and the Synox OxyOzone process meets the criteria ofpathogen monitoring from influent to effluent
BIOSOLIDS MANAGEMENT 45
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Reduction of Vector Attraction
Vector-attraction reduction may be classified as long-term or short-termstabilization or may be accomplished through physical barriers Long-termstabilization is defined as the biological degradation of the putrescible organicsand results in a reduction of vector attraction One of 10 options may be used tosatisfy vector control The first five options below are considered long-termstabilization and the next three are considered short-term stabilization (inhibitbiological activity before application) and must be demonstrated at the time ofuse to ensure that the criteria are satisfied It should be stressed that whenbiosolids are applied to land the vector-attraction-reduction requirements mustbe satisfied This can be a potential issue with the short-term options since theyare reversible It should also be noted that treatment should be complete prior toland application so that further reaction does not occur in the field which mayresult in the release of odorants One of the following eight vector controlrequirements may be used to qualify as EQ biosolids
Volatile Solids Reduction The mass of volatile solids in the sewagesludge shall be reduced by a minimum of 38
Specific Oxygen Uptake Rate The specific oxygen uptake rate (SOUR)for aerobic sewage sludge shall be equal to or less than 15 milligrams (mg) ofoxygen per hour per gram of TS on a dry-weight basis corrected to 20degC
Anaerobic Bench-Scale Test Demonstrate through additional digestionin a bench-scale test that additional volatile solids reduction for anaerobicallydigested sewage sludge is less than 17 This can be demonstrated byanaerobically digesting a portion of the previously digested sewage sludge inthe laboratory in a bench-scale unit for 40 additional days at a temperaturebetween 30degC and 37degC This requirement is satisfied when at the end of thetest volatile solids have been reduced by less than 17 as measured from thebeginning to the end of the test
Aerobic Bench-Scale Test Demonstrate through additional digestion in abench-scale test that additional volatile solids reduction for aerobically digestedsewage sludge is less than 15 This can be demonstrated by aerobicallydigesting a portion of the previously digested sewage sludge at a concentrationof 2 solids or less in the laboratory in a bench-scale unit for 30 additionaldays at a temperature of 20degC Sewage sludge with a higher percentage of solidsmust be diluted with effluent down to 2 at the start of the test Thisrequirement is satisfied when at the end of the test volatile solids have beenreduced by less than 15 as measured from the beginning to the end of the test
BIOSOLIDS MANAGEMENT 46
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Aerobic Process (for Compost) The sewage sludge must be treated in anaerobic process for 14 days or longer During that time the temperature of thesewage sludge must be higher than 40degC and the average temperature of thesewage sludge must be higher than 45degC
pH Adjustment The pH of the sewage sludge must be raised to 12 orhigher by alkali addition and without the addition of more alkali remain at 12or higher for 2 h and then at 115 or higher for an additional 22 h
Drying Without Primary Solids The percent solids of sewage sludgethat does not contain unstabilized solids generated in a primary wastewatertreatment process shall be equal to or greater than 75 based on the moisturecontent and total solids prior to mixing with other materials
Drying with Primary Solids The percent solids of sewage sludge thatcontains unstabilized solids generated in a primary wastewater treatmentprocess shall be equal to or greater than 90 based on the moisture content andtotal solids prior to mixing with other materials
In place of the process-based requirements one of the following tworequirements may be utilized during or after land application and are consideredphysical barriers to vector attraction
Injection No significant amount of the biosolids can be present on theland surface within 1 h of biosolids injection
Incorporation The biosolids must be incorporated within 6 h of surfaceapplication or as approved by the permit authority
Table 2ndash3 summarizes the above requirements
Treatment Design Standards
Sewage sludge treatment technology not only provides the primarymechanism for pathogen reduction and the necessary stabilization to reducebiosolids attraction as a food source for vectors but also provides the means toreduce odors and related public nuisance and public health concerns Although40 CFR 503 provides prescriptive standards for treatment process control theGreat Lakes-Upper Mississippi River Board of State and Provincial PublicHealth and Environment Managers (GLUMB) report Recommended Standardsfor Wastewater Facilities (GLUMB 1997) (commonly referred to as the ldquoTenStates Standardsrdquo) is used as a basis for minimum design requirements in manystates but does not require the minimum criteria for many of the PSRPs Thecommittee concludes that tightening the minimum treatment
BIOSOLIDS MANAGEMENT 47
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t th
is P
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file
Thi
s ne
w d
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l rep
rese
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of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TA
BL
E 2
ndash3 S
umm
ary
of R
equi
rem
ents
for
Vec
tor
Att
ract
ion
Red
ucti
on U
nder
Par
t 503
Req
uire
men
tW
hat I
s R
equi
red
Mos
t App
ropr
iate
for
O
ptio
n 1
503
33(b
)(1)
At l
east
38
red
uctio
n in
vol
atile
sol
ids
duri
ng s
ewag
e sl
udge
trea
tmen
tS
ewag
e sl
udge
pro
cess
ed b
yndashA
naer
obic
bio
logi
cal t
reat
men
tndashA
erob
ic b
iolo
gica
l tre
atm
ent
ndashChe
mic
al o
xida
tion
Opt
ion
250
333
(b)(
2)L
ess
than
17
add
itio
nal
vola
tile
sol
ids
loss
dur
ing
benc
h-sc
ale
anae
robi
c ba
tch
dige
stio
n of
the
sew
age
slud
ge f
or 4
0 ad
ditio
nal
days
at 3
0degC
to 3
7degC
(86
degF to
99deg
F)
Onl
y fo
r an
aero
bica
lly
dige
sted
sew
age
slud
ge
Opt
ion
350
333
(b)(
3)L
ess
than
15
add
itio
nal
vola
tile
sol
ids
redu
ctio
n du
ring
ben
ch-
scal
e ae
robi
c ba
tch
dige
stio
n fo
r 30
add
itio
nal d
ays
at 2
0degC
(68
degF)
Onl
y fo
r ae
robi
call
y di
gest
ed s
ewag
e sl
udge
wit
h 2
or
less
sol
ids
Opt
ion
450
333
(b)(
4)S
OU
R a
t 20deg
C (
68degF
) is
`1
5 m
g of
oxy
gen
hg
tota
l sew
age
slud
ge s
olid
sS
ewag
e sl
udge
s fr
om a
erob
ic p
roce
sses
(sh
ould
not
be
used
for
com
post
ed s
ewag
e sl
udge
s)O
ptio
n 5
503
33(b
)(5)
Aer
obic
trea
tmen
t of
the
sew
age
slud
ge f
or a
t lea
st 1
4 da
ys a
tov
er 4
0degC
(10
4degF
) w
ith
an a
vera
ge te
mpe
ratu
re o
f ov
er 4
5degC
(113
degF)
Com
post
ed s
ewag
e sl
udge
(O
ptio
ns 3
and
4 a
re li
kely
to b
e ea
sier
to m
eet f
or s
ewag
e sl
udge
s fr
om o
ther
aer
obic
pro
cess
es)
Opt
ion
650
333
(b)(
6)A
ddit
ion
of s
uffi
cien
t alk
ali t
o ra
ise
the
pH to
at l
east
12
at 2
5degC
(77deg
F)
and
mai
ntai
n a
pH `
12
for
2 h
and
a pH
`1
15
for
22m
ore
hour
s
Alk
ali-
trea
ted
sew
age
slud
ge (
alka
lies
incl
ude
lim
e f
ly a
sh k
iln
dust
and
woo
d as
h)
Opt
ion
750
333
(b)(
7)P
erce
nt s
olid
s `7
5
pri
or to
mix
ing
wit
h ot
her
mat
eria
lsS
ewag
e sl
udge
s tr
eate
d by
an
aero
bic
or a
naer
obic
pro
cess
(ie
se
wag
e sl
udge
s th
at d
o no
t con
tain
uns
tabi
lized
sol
ids
gene
rate
d in
prim
ary
was
tew
ater
trea
tmen
t)
BIOSOLIDS MANAGEMENT 48
Abou
t th
is P
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file
Thi
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igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Opt
ion
850
333
(b)(
8)P
erce
nt s
olid
s `9
0
pri
or to
mix
ing
wit
h ot
her
mat
eria
lsS
ewag
e sl
udge
s th
at c
onta
in u
nsta
biliz
ed s
olid
s ge
nera
ted
inpr
imar
y w
aste
wat
er tr
eatm
ent (
eg
any
hea
t-dr
ied
sew
age
slud
ges)
Opt
ion
950
333
(b)(
9)B
ioso
lids
are
inje
cted
into
soi
l so
that
no
sign
ific
ant a
mou
nt o
fse
wag
e sl
udge
is p
rese
nt o
n th
e la
nd s
urfa
ce1
h af
ter
inje
ctio
n e
xcep
t Cla
ss A
bio
solid
s w
hich
mus
t be
inje
cted
wit
hin
8 h
afte
r th
e pa
thog
en r
educ
tion
pro
cess
Bio
soli
ds a
ppli
ed to
the
land
or
sew
age
slud
ge p
lace
d on
asu
rfac
e di
spos
al s
ite
dom
esti
c se
ptag
e ap
plie
d to
agr
icul
tura
lla
nd a
for
est
or a
rec
lam
atio
n si
te o
r pl
aced
on
a su
rfac
edi
spos
al s
ite
Opt
ion
1050
333
(b)(
10)
Bio
soli
ds a
re in
corp
orat
ed in
to th
e so
il w
ithi
n 6
h af
ter
appl
icat
ion
to la
nd o
r pl
acem
ent
on a
sur
face
dis
posa
l sit
e e
xcep
tC
lass
A b
ioso
lids
whi
ch m
ust b
e ap
plie
d to
or
plac
ed o
n th
e la
ndsu
rfac
e w
ithi
n 8
h of
the
path
ogen
red
ucti
on p
roce
ss
Bio
soli
ds a
ppli
ed to
the
land
or
sew
age
slud
ge p
lace
d on
asu
rfac
e di
spos
al s
ite
dom
esti
c se
ptag
e ap
plie
d to
agr
icul
tura
lla
nd f
ores
t or
a r
ecla
mat
ion
site
or
plac
ed o
n a
surf
ace
disp
osal
site
Opt
ion
1150
333
(b)(
11)
Sew
age
slud
ge p
lace
d on
a s
urfa
ce d
ispo
sal s
ite
mus
t be
cove
red
wit
h so
il o
r ot
her
mat
eria
l at t
he e
nd o
f ea
ch o
pera
ting
day
Sew
age
slud
ge o
r do
mes
tic
sept
age
plac
ed o
n a
surf
ace
disp
osal
site
Opt
ion
1250
333
(b)(
12)
pH o
f do
mes
tic
sept
age
mus
t be
rais
ed to
`1
2 at
25deg
C (
77degF
) by
alka
li a
dditi
on a
nd m
aint
aine
d at
`1
2 fo
r 30
min
with
out a
ddin
gm
ore
alka
li
Dom
esti
c se
ptag
e ap
plie
d to
agr
icul
tura
l lan
d a
for
est
or a
recl
amat
ion
site
or
plac
ed o
n a
surf
ace
disp
osal
sit
e
Sour
ce A
dapt
ed f
rom
EPA
199
9b
BIOSOLIDS MANAGEMENT 49
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t th
is P
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file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
design standards by control agencies and GLUMB to reflect and beconsistent with the requirements of 40 CFR 503 would accomplish much in thearea of compliance and odor abatement Since odors are a primary source ofpublic complaints adequacy of treatment cannot be over-emphasized Odors area function of treatment quality and are minimized with effective treatment andmanagement
Rule Modifications
Two lawsuits were brought shortly after the 1993 rule promulgationinvolving three chemical pollutants (chromium selenium and molybdenum)that caused modifications to the land application section of 40 CFR 503 Thefirst lawsuit centered on the fact that the pollutant concentrations for chromiumand selenium were not based on risk and the petition argued that EPA wasrequired under the CWA to establish such limits based only on risk The courtagreed and required that the risk-based values become the pollutantconcentrations in all cases This meant that the ceiling concentrations in thosecases would also be the risk-based number (The pollutant limit for seleniumwas therefore increased from 36 [99] to 100 milligrams per kilogram [mgkg][risk based]) The suit also charged that the research used to assessphytotoxicity as the limiting pathway for chromium was based on pot studiesand not field research which showed no such effects The court again agreedbut EPA chose not to replace the standard with the next limiting pathwaybecause it would set the limit at 12000 mgkg Determining that no biosolidswould have chromium concentrations that high chromium was deleted fromregulation under 40 CFR 503 (EPA 1995b)
The second lawsuit asserted that the research used to determine thelimiting pathway for molybdenum (animal ingesting feed grown on biosolids-treated fields) was not scientifically supportable and calculated amounts ofmolybdenum that plants take in (eg plant uptake slopes) were based on highlycontaminated sewage sludge EPA agreed to conduct more research to betterestablish risk levels At this time the cumulative loading limit and pollutantconcentration limits have been deleted for molybdenum and only the ceilingconcentration remains (see Table 2ndash1) (EPA 1994) OrsquoConnor et al (2001)conducted a modified risk assessment and recommended values for the deletedtables However EPA has not acted to revise the molybdenum standard
BIOSOLIDS MANAGEMENT 50
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t th
is P
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file
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s ne
w d
igita
l rep
rese
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of t
he o
rigin
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ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Revision of Regulations
EPA was court-ordered to promulgate a second round of 40 CFR 503regulations by December 15 2001 In response EPA conducted a pollutantscreening hazard identification exercise and subsequently determined that theonly pollutants posing a potential risk that were not regulated in the first roundwere dioxin and dioxin-like compounds On December 23 1999 EPApublished proposed risk-based regulations for 7 dioxin 10 furan and 12coplanar PCB congeners (EPA 1999c) Once again EPA received numerouscomments on the proposal representing an array of perspectives As a result ofthe public comments received EPA contracted for a new biosolids survey toevaluate biosolids concentrations of the congeners of interest contracted for anew risk assessment using probabilistic or Monte Carlo simulation methodsrather than the deterministic methods used for the proposed rule and engaged apeer-review panel Agreement was recently reached between all parties toextend the deadline for the Round 2 land-application rule until October 172003 EPA (2002a) published a Notice of Data Availability on June 12 2002that summarizes new data and a revised risk assessment
Public Issue Forums
A number of public forums have been critical of the final Part 503regulations or of EPArsquos commitment to oversight in implementing theregulations The criticisms include the following
bull After promulgation of the Part 503 regulations in 1993 EPA decided thatthe land application of biosolids was a low risk to public health andtherefore the biosolids oversight program was given a low priority in itsannual budget That decision was based on the aggregate risk assessmentwhich showed negligible adverse effects even without regulationHowever the decision has had far-reaching negative consequences andhas forced the agency and state programs to operate in a conflictresolution mode rather than in an efficient proactive mode As a resultresources are expended only after a problem is identified rather thanworking to avoid the problem in the first place This policy decisionprovides little flexibility for dealing with perceived effects or emergingissues
bull A committee of the National Research Council (NRC) was convened in1993 to examine the science behind the federal biosolids regulations andthe use of biosolids on food-chain crops The NRC (1996) reportconcluded that ldquoif the regulations are properly adhered to the use of[biosolids] on food-
BIOSOLIDS MANAGEMENT 51
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t th
is P
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file
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s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
chain crops for human consumption is protective of human healthrdquo Thereport also recommended that additional research be conducted in certainareas particularly in pathogen control and that EPA take steps to ensurethat the regulations were followed (see also Chapter 1 and Box 1ndash2 formore detail on that committeersquos recommendations)
bull There have been several allegations of human deaths and illnesses causedby land application of biosolids However there has been no documentedscientific evidence to substantiate those claims
bull There have also been several allegations of animal deaths caused by landapplication of biosolids (eg cases in Colorado and Georgia) Supportingevidence to substantiate these allegations has not been documented in thescientific literature but EPA did investigate them and has producedreports on their findings23 It found no substantiation for the allegations
bull The National Institute for Occupational Safety and Health (NIOSH)published a Hazard ID 10 (NIOSH 2000) in August 2000 based on aHealth Hazard Evaluation Report (Burton and Trout 1999) The reportswere based on an investigation of worker health effects at theLeSourdsville Ohio wastewater treatment facility owned and operatedby the Butler County Health Department The workers were involved inthe treatment storage and land application of sewage sludge There was alapse between the time of the workers becoming ill and the involvementof NIOSH At the time of the illnesses LeSourdsville had operatingdifficulties and the sewage sludge produced did not meet the Class Bbiosolids requirements (Lodor 2001) For example the sewage sludge hadfecal coliform densities more than 4 times the allowed limit At the timeof the NIOSH inquiry in 1999 coliform densities were well below thelimit However it was also found that good hygiene protocol was notgenerally followed by the biosolids workers thus precluding any relevantcorrelations NIOSH recently released guidance for controlling potentialrisks to workers exposed to Class B biosolids (NIOSH 2002) Thisdocument supercedes the Hazard ID 10 document
bull A congressional hearing before the Committee on Science chaired byCongressman FJames Sensenbrenner Jr was held on March 22 2000 tohold EPA accountable for how it dealt with criticism and the public ingeneral regarding its biosolids program (The hearing was not intended toquestion the science behind the existing regulations see also Kester2000a)
2DHGould GHLoneragan Integrated Livestock Management Group GKBeckand HDFraleigh Colorado State University and RBBrobst EPA unpublished datano date
3JWGaskin and EWTollner University of Georgia unpublished data no date
BIOSOLIDS MANAGEMENT 52
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t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
bull An independent program audit by the EPA Office of the Inspector General(OIG) (EPA 2000b) requested by the EPA Office of Water (OW)concluded that there was a significant lack of oversight and resourcescommitted by the EPA Office of Enforcement and Compliance Assurance(OECA) the Office of Wastewater Management (OWM) the Office ofScience and Technology (OST) and the Office of Research andDevelopment (ORD) Therefore EPA could not guarantee that land-application and public-distribution practices were conducted incompliance with the CWA regulations and thus protective of public healthand the environment Notably the Inspector General did not claim thatthe regulations were not protective but rather criticized EPArsquos inability toconfirm compliance However OW and OECA officially declined to takeaction on many of the OIGrsquos recommendations due to budgetaryconstraints and other program priorities (EPA 2000c 2001a) The OIGsubsequently sent a letter stating that OWrsquos and OECArsquos formal responsewas inadequate The OIG suggested alternative means for fulfilling thereport recommendations and broadly criticized the lack of commitment tothe biosolids program and the absence of consensus regarding programimplementation within EPA (EPA 2001b) They also requested a timelinefrom OW and OECA for establishing a new biosolids goal and identifyingneeded resources to accomplish it under the Government Performanceand Results Act (GPRA) The OW and OECA responded with a letter(EPA 2002b) stating that to fulfill the OIG recommendations wouldrequire budget and staff resources the agency simply did not have Thusthe OW and OECA position continues to be that biosolids are a low riskto human health and the environment Given the ongoing need for OWand OECA to set priorities among its many programs concerning publichealth and environmental protection they maintain that their limitedresources are better allocated elsewhere
bull In late 2000 EPA requested and sponsored an NRC study to reviewinformation on the land application of biosolids and reexamine the risk-assessment methods used in developing the Part 503 regulations in lightof recent research findings and advances in risk assessment to determinewhether the standards were still adequately protective of human healthThis study is also reviewing pathogen control whether a risk-basedapproach for pathogens should be pursued and whether chemical andpathogen risk-assessment approaches can be integrated This report is theproduct of that committee
bull The EPA OIG released a status report of EPArsquos biosolids program inMarch 2002 (EPA 2002c) The major findings of the report were
- EPA places a low priority on the biosolids program and the number ofprogram staff assigned to it have been declining
- EPA has delegated authority of the biosolids program to only five statesEPA cannot be certain that all citizens in nondelegated states areprovided at least the same level of protection as in the federal program
BIOSOLIDS MANAGEMENT 53
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t th
is P
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file
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s ne
w d
igita
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of t
he o
rigin
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ork
has
been
rec
ompo
sed
from
XM
L fil
es c
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ed f
rom
the
orig
inal
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er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
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ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
- There can be wide variation in how states manage biosolids- EPA has no formal process for tracking health complaints Of 21
complaints that were brought to the OIGrsquos attention 14 wereinvestigated by EPA or a state agency five were not report to EPA orthe state and two were not related to biosolids
- EPA has no plans for conducting a comprehensive evaluation andmonitoring study to address risk assessment uncertainties Moreresearch on pathogen testing appears to be needed
- In reviewing EPArsquos relationship with the Water Environment Federation(WEF) OIG found that 96 of the $129 million given to WEF and itsresearch organization over a 3-year period was congressionallymandated and EPA had no discretion in awarding the funds
- The general public has concerns about the effects of biosolids on healthquality of life and natural resources Public perception of landapplication of biosolids has a significant impact on the implementationof the program
EPA Resources
The committee notes that it has long been recognized by those within EPAworking in the biosolids field and state agencies required to implement thebiosolids program that EPA disinvestment in the program has caused aninability to adequately ensure that the regulations are followed Although morethan 40 of the capital cost and the operation and maintenance expense ofwastewater treatment is expended on biosolids treatment and management(much of which is from federal dollars in the form of grants and low-interestloans) less than one-tenth of 1 of EPArsquos budget is devoted to the biosolidsprogram Of EPArsquos $78 billion budget in FY 2001 only about $4 million or005 was devoted to biosolids staff and the program (JWalker EPApresentation at Biosolids Regulator Workshop Potomac Maryland June 282001)
The Wisconsin Department of Natural Resources (WDNR) represents allstate environmental protection agencies to EPA including the EPA BiosolidsProgram Implementation Team (BPIT) on a number of biosolids issues In thiscapacity the WDNR has sent five letters to EPA between 1998 and 2001seeking program support (Meyer 1998 Kester 2000bc 2001ab) The areas ofmost critical need include technical support on biosolids treatment for pathogenand vector-attraction controls and staffing The Pathogen EquivalencyCommittee (PEC) comprises agency experts who primarily serve as volunteersto provide technical support regarding the adequacy of treatment technologywith respect to pathogen control Each of the 10 EPA Regions
BIOSOLIDS MANAGEMENT 54
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t th
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igita
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ntat
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of t
he o
rigin
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ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
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as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
have between 02 and 2 full-time employees (FTEs) and a total nationwide of88 FTEs working in all areas of biosolids management The EPA ORD has 2FTEs devoted to the program and EPA headquarters has 48 FTEs (JWalkerEPA presentation at Biosolids Regulator Workshop Potomac Maryland June28 2001) In addition to these obvious staff shortages consideration should begiven to train new experts in the field to replace existing staff many of who areapproaching retirement
State Programs
Many states are responsible for implementing biosolids programs by theirown statutes and regulations In those states biosolids application falls underboth EPA and state rules with federal rules being required minimum standardsSome municipalities (or local units of government) in the United States haveadopted local ordinances pertaining to land application The authority of amunicipality and thus the scope that a local ordinance can address variesbetween the states (Harrison and Eaton 2001) Thus the ability of a localordinance to withstand legal challenge depends on the state As notedpreviously only five states (Oklahoma Utah Texas Wisconsin and SouthDakota) have received official delegated authority from EPA to administer thefederal regulations for biosolids Several states have submitted requests fordelegated authority but in many cases experience long waiting periods for areview of that request (eg Vermont and Iowa) or encounter other legal ortechnical roadblocks For example Colorado Indiana and South Carolina havehad legal issues with self-audit protection laws which are inconsistent withfederal requirements North Carolina has issues with implementing agreementscompliant with endangered species protection administered through the USFish and Wildlife Service and Michigan has potential issues with authority overnon-Native-American wastewater generated or used on Native American landNevertheless all states have varying degrees of commitment for biosolidsprogram administration Figure 2ndash3 shows the number of full-time employees(FTEs) working for state biosolids programs This figure is based on directcommunication between the WDNR and each state (WDNR unpublished data2001)
EUROPEAN BIOSOLIDS MANAGEMENT
The management of biosolids in Europe varies from country to country asdo the standards applied their derivation and their enforcement This situationis readily apparent when US regulations and their varying levels of
BIOSOLIDS MANAGEMENT 55
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ompo
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from
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L fil
es c
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inal
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er b
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igin
al ty
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tting
file
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age
brea
ks a
re tr
ue to
the
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inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
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ome
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grap
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rs m
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ave
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ibut
ion
FIG
UR
E 2
ndash3 N
umbe
r of
FT
Es
dedi
cate
d to
sta
te b
ioso
lids
pro
gram
s F
igur
es d
o no
t inc
lude
sep
tage
sta
ff S
ourc
e E
PA
200
2c
BIOSOLIDS MANAGEMENT 56
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brea
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ther
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peci
fic fo
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ting
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ever
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his
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enforcement are compared with those of European countries Some of thesubstantial differences in the contaminant standards between Europe and theUS are in part due to differences in approaches to environmental protectionand regulatory intent (public health and environmental protection) Forexample some European countries have taken the approach of minimizing anyaccumulation of metals beyond background environmental levels whereasother European countries and the US have performed risk assessments todetermine land-application concentrations that are protective of reasonablyanticipated adverse effects Even the latter approach has lead to substantiallydifferent standards between some countries A variety of factors influence theoutcomes of risk assessment (discussed in Chapter 5) but the majorcontributing factor to different risk-based standards between countries is eachcountryrsquos selection of target organism (humans animals plants soil organisms)to protect Although it was beyond the scope of this report to prepare acomprehensive evaluation of differences between US standards and those ofother countries it is important that the differences be acknowledged and thebases for those differences used to inform future risk assessments This sectionprovides an overview of how different European countries have approached themanagement of biosolids for land application
The European Union is composed of 15 member nations The Council ofEuropean Communities (1986) published the Sewage Sludge Directive (86278EEC) All members had to promulgate their own version of the directive asnational regulations by 1989 The directive included a recommended range ofpollutant concentration values for seven constituents in biosolids for membernations to use in adopting their standards (see Table 2ndash4) However individualnations could choose to adopt more stringent standards than thoserecommended in the directive New regulations were proposed but might not beadopted until 2005 (Luca Marmo European Commission Brussels personalcommunication 2002)
A comprehensive review of biosolids use and disposal practices waspublished by the International Association on Water Quality (IAWQ)International Water Association (IWA) the Water Environment Federation(WEF) and the European Water Pollution Control Association (EWPCA)(Matthews 1996) Selected information from that review and other referenceshas been presented with appropriate updates when available (Council of theEuropean Communities 1986 EPA 1990 1995ab 1999b Gendebien et al1999 European Union 2000ab and European Communities 2001)Accordingly representative data from Europe to complement US informationhave been assembled to provide a basis for comparison and some determinationof the current and future status of biosolids management
BIOSOLIDS MANAGEMENT 57
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sed
from
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brea
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ther
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setti
ng-s
peci
fic fo
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ting
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ever
can
not b
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TABLE 2ndash4 European Union Limit Values for Concentrations of Heavy Metals inBiosolids for Use on Land
Limit Values (mgkg of DM)Elements Directive 86278EEC ProposedCadmium 20ndash40 10Chromium - 1000Copper 1000ndash1750 1000Mercury 16ndash25 10Nickel 300ndash400 300Lead 750ndash1200 750Zinc 2500ndash4000 2500
Abbreviation DM dry matterSource Adapted from Council of the European Communities 1986
An assessment of the status of disposal and recycling within the Europeancommunity (European Communities 2001) reviewed existing legislation andregulations and provided an analysis of stakeholder positions motivations andconstraints as well as solutions for reducing constraints and encouraging theuse of biosolids Analysis of existing legislation indicated that specificrequirements focus principally on the use of biosolids in agriculture bothnationally and in Europe The EEC directives which have the strongestinfluence on biosolids use are directive 91271EEC on urban wastewatertreatment and 86278EEC on the use of biosolids in agriculture (Council of theEuropean Communities 1986) Requirements set by the latter directive are acrucial element in the management of biosolids produced in the member statesand some member states have introduced provisions that go beyond therequirements of the directive In particular the limit values for concentrationsof heavy metals in biosolids are lower than those specified in the directive in amajority of the countries
As indicated in Table 2ndash5 the countries in which the limitations on heavymetal concentrations are the most stringent are Belgium (Flanders region)Denmark Finland the Netherlands and Sweden Greece Luxembourg IrelandItaly Portugal and Spain have set limit values similar to those in the directivevalues for Poland an accession country are also lower than the EuropeanUnion standards The United Kingdom legislation differs by not providing anylimit values for heavy metals in biosolids but rather specifying the maximumannual average loads of heavy metals to soil that are similar to the directive(Table 2ndash6) In addition the regulations on biosolids use include limit valuesfor pathogens in France Italy and Luxembourg and for organic
BIOSOLIDS MANAGEMENT 58
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TA
BL
E 2
ndash5 E
urop
ean
Uni
on L
imit
Val
ues
for
Hea
vy M
etal
s in
Bio
soli
ds m
illi
gram
s pe
r ki
logr
am o
f dr
y m
atte
r (D
M)
(Ita
lic
num
bers
rep
rese
nt li
mit
valu
es b
elow
thos
e re
quir
ed b
y di
rect
ive
862
78E
EC
)C
dC
rC
uH
gN
iP
bZ
nA
sM
oC
oD
irec
tive
86
278
EE
C20
ndash 40
-1
000 ndash
175
016
ndash 25
300 ndash
400
750ndash
120
02
500 ndash
400
0-
--
Aus
tria
2a50
a30
0a2a
2510
0a1
500a
--
10a
10b
500b
500b
10b
100b
400b
200
0b-
--
10c
500c
500c
10c
100c
500c
200
0c-
--
4d30
0d50
0d4d
100d
150d
180
0d-
--
10e
500e
500e
10c
100e
500c
200
0c20
c20
c10
0c
07ndash
25f
70ndash1
00f
70ndash3
00f
04ndash
25f
25ndash8
0f45
ndash150
f20
0ndash1
800f
--
-B
elgi
um (
Flan
ders
)6
250
375f
510
030
090
0f15
0-
-B
elgi
um (
Wal
loon
)10
500
600
1010
050
02
000
--
Den
mar
k-
dry
mat
ter
basi
s0
810
01
000
08
3012
g4
000
25h
--
- to
tal p
hosp
horu
s ba
sis
100
200
250
010
000
g
Fin
land
330
060
02
100
150
150
0-
--
15i
1i10
0I
Fra
nce
20j
100
01
000
1020
080
03
000
--
-G
erm
any
1090
080
08
200
900
250
0-
--
Gre
ece
20ndash 4
050
010
0ndash1
750
16ndash 2
530
0 ndash40
075
0ndash12
002
500 ndash
400
0-
--
BIOSOLIDS MANAGEMENT 59
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
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ompo
sed
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er b
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age
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ther
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ng-s
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ting
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grap
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rs m
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iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Cd
Cr
Cu
Hg
Ni
Pb
Zn
As
Mo
Co
Dir
ecti
ve 8
627
8E
EC
20ndash 4
0-
100
0 ndash1
750
16ndash 2
530
0ndash40
075
0 ndash1
200
250
0 ndash4
000
--
Irel
and
20-
100
016
300
750
250
0-
--
Ital
y20
mdash1
000
1030
075
02
500
--
-L
uxem
bour
g20
ndash 40
100
0 ndash1
750
100
0 ndash1
750
16ndash2
530
0ndash40
075
0ndash1
200
250
0ndash4
000
--
-N
ethe
rlan
ds1
2575
750
7530
100
300
--
-P
ortu
gal
2010
001
000
1630
075
02
500
--
-S
pain
- so
il p
H lt
720
100
01
000
1630
075
02
500
--
--
soil
pH
gt7
401
750
175
025
400
120
04
000
Sw
eden
210
060
02
550
100
800
--
-U
nite
d K
ingd
om-
--
--
--
--
-A
cces
sion
cou
ntri
esE
ston
ia15
120
080
016
400
900
290
0-
--
Lat
via
202
000
100
016
300
750
250
0-
--
Pol
and
1050
080
05
100
500
250
0-
--
a Low
er A
ustr
ia (
grad
e II
)b U
pper
Aus
tria
c B
urge
nlan
dd V
orar
lber
g
BIOSOLIDS MANAGEMENT 60
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
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ed f
rom
the
orig
inal
pap
er b
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pese
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brea
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lin
e le
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s w
ord
brea
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ther
type
setti
ng-s
peci
fic fo
rmat
ting
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ever
can
not b
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tain
ed a
nd s
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grap
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rs m
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tally
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rted
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sion
of t
his
publ
icat
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as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
e Ste
ierm
ark
f Car
inth
ia
f The
se v
alue
s w
ill b
e re
duce
d to
125
(C
u) a
nd 3
00 (
Zn)
fro
m D
ecem
ber 3
1 2
007
g For
pri
vate
gar
deni
ng l
ead
valu
e is
red
uced
to 6
0 m
gkg
of
DM
or
500
0 m
gkg
of
phos
phor
us
h For
pri
vate
gar
deni
ng
i Tar
get l
imit
valu
es f
or 1
998
j 15
mg
kg o
f D
M f
rom
Jan
uary
1 2
001
and
10 m
gkg
of
DM
fro
m J
anua
ry 1
200
4A
bbre
viat
ions
As
ars
enic
Cd
cad
miu
m C
o c
obal
t C
r c
hrom
ium
Cu
cop
per
Hg
mer
cury
Mo
mol
ybde
num
Ni
nick
el P
b le
ad Z
n z
inc
Sour
ce A
dapt
ed f
rom
Eur
opea
n C
omm
unit
ies
2001
BIOSOLIDS MANAGEMENT 61
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TABLE 2ndash6 European Union Limit Values for Amounts of Heavy Metals That MayBe Added Annually to Soil Based on a 10-Year Average
Limit Values (ghay)Elements Directive 86278EEC ProposedCadmium 150 30Chromium - 3000Copper 12000 3000Mercury 100 30Nickel 3000 900Lead 15000 2250Zinc 30000 7500
Note The component authority may decide to allow an increase in the loading rate for copper andzinc on a case-by-case basis for those plots of land that are copper-or zinc-deficient and if it hasbeen proved by qualified expert advice that there is a specific agronomic need for the cropsAbbreviations ghay gram per hectare per yearSources Adapted from Council of the European Communities 1986 European Union 2000b
compounds in Austria Belgium-Flanders Denmark France Germany andSweden neither of which are included in the directive (Tables 2ndash7 and 2ndash8)
In all member states regulations on the use of biosolids specify limitvalues for heavy metals in soil that are similar in most cases to the requirementsset in the directive (Table 2ndash9) Some countries have defined limit values forseveral categories of soil pH or limit the maximum load of heavy metals toagricultural lands on a 10-year basis Maximum quantities of biosolids that canbe applied on land have been set between 1 metric ton by the Netherlands forgrasslands and 10 metric tons by Denmark per hectare and per year
The debate on biosolids recycling and disposal differs in intensity andresolution throughout the European community An analysis of stakeholdergroups (European Communities 2001) including the farming communitylandowners industries water and wastewater plants and companies localauthorities national authorities and citizens and consumer groups indicated asignificant diversity of opinion ranging from opposition to advocacy as shownbelow
BIOSOLIDS MANAGEMENT 62
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t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
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ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
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tally
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Ple
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t ver
sion
of t
his
publ
icat
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as th
e au
thor
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rsio
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r attr
ibut
ion
TABLE 2ndash7 European Limit Values for Pathogens Concentrations in Biosolids
Salmonella Other PathogensFrance 8 MPN10 g of DM Enterovirus 3 MPCN10 g of DM
Helminths eggs 310 g of DMItaly 1000 MPNg of DMLuxembourg Enterobacteria 100g
No egg of worm likely to becontagious
Poland Biosolids cannot be used inagriculture if it containsSalmonella
ldquoParasitesrdquo 10kg of DM
Abbreviations DM dry matter MPN most probable number MPCN most probable cytophaticnumberSource Adapted from European Communities 2001
bull The regulatory requirements in the Netherlands and Flanders region ofBelgium have prevented almost all use of biosolids in agriculture since1991 and 1999 respectively
bull In countries such as Denmark and the United Kingdom new regulationsare considered sufficiently strict to reduce risks to an acceptable level(Denmark) and agreement in 1998 between water and sewage operatorsand retailers as well as farmersrsquo associations and government (UnitedKingdom) led to the joint adoption of a ldquosafe sludge matrixrdquo providing foradditional restrictions on the use of biosolids on agricultural land as wellas the categories of crops on which biosolids may not be used
bull In Sweden a voluntary agreement was signed in 1994 between theSwedish Environmental Protection Agency the Swedish Federation ofFarmers (LRF) and the Swedish Water and Waste Water Associationconcerning quality assurances relating to the use of biosolids inagriculture However in October 1999 the LRF recommended that itsmembers stop using biosolids because of quality concerns
bull Public opinion in Germany has recently swung in favor of agriculturalland application mainly because this practice is considered economicallyviable and the potential risks are sufficiently reduced by the existinglegislation which is now being reviewed
bull In Austria France and the Walloon region of Belgium national (orregional) agreements have been considered and in France such anagreement
BIOSOLIDS MANAGEMENT 63
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
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L fil
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ther
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nd s
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grap
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Ple
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prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TA
BL
E 2
ndash8 E
urop
ean
Lim
it V
alue
s fo
r O
rgan
ic C
ompo
unds
in B
ioso
lids
(m
illi
gram
s pe
r ki
logr
am o
f dr
y m
atte
r)
Dio
xins
and
Fur
ans
(PC
DD
PC
DF
) ng
TE
kg
of D
MPC
Bs
AO
XL
AS
DE
HP
NP
EP
AH
Tol
uene
Aus
tria
100a
bc
50e
02a
bc
1e50
0ab
d-
--
6d-
Bel
gium
(Fl
ande
rs)e
Den
mar
k-
--
260
010
050
6-
from
10
720
001
300
5030
3fr
om 1
07
2002
130
050
103
Fra
nce
-0
8f-
--
2ndash5g
15ndash
4h-
Ger
man
y10
00
2i50
0-
--
--
Sw
eden
-0
4-
-10
03
5a L
ower
Aus
tria
b U
pper
Aus
tria
c V
orar
lber
gd C
arin
thia
e L
imit
valu
es f
or a
ppro
xim
atel
y 30
org
anic
com
poun
ds
f Sum
of
seve
n pr
inci
pal P
CB
s (P
CB
28
52
101
118
138
153
180
)g F
luor
anth
ene
ben
zo[b
]flu
oran
then
e b
enzo
[a]p
yren
eh W
hen
used
on
past
ure
land
i F
or e
ach
one
of th
e si
x c o
ngen
ers
BIOSOLIDS MANAGEMENT 64
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
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ompo
sed
from
XM
L fil
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reat
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rom
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inal
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file
s P
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the
orig
inal
lin
e le
ngth
s w
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ther
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setti
ng-s
peci
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ever
can
not b
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grap
hic
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iden
tally
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Ple
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prin
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of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TA
BL
E 2
ndash9 E
urop
ean
Uni
on L
imit
Val
ues
for
Hea
vy M
etal
s in
Soi
l (m
illi
gram
s pe
r ki
logr
am o
f dr
y m
atte
r) (
Sha
ded
cell
s re
pres
ent l
imit
val
ues
belo
wth
ose
requ
ired
by
Dir
ecti
ve 8
627
8E
EC
)C
dC
rC
uH
gN
iP
bZ
nA
sM
oC
oD
irec
tive
86
278
EE
C (
6ltpH
lt7)
1ndash3
mdash50
ndash 140
1ndash1
530
ndash75
50ndash 3
0015
0ndash30
0-
--
Aus
tria
15a
100a
60a
1a50
a10
0a20
0a-
--
1b10
0b10
0b1b
60b
100b
300b
--
-2c
100c
100c
15c
60c
100c
300c
--
-2d
100d
100d
1d60
d10
0d30
0d-
--
2e10
0e10
0e1e
60e
100e
300e
-10
e50
e
05ndash
15f
50ndash1
00f
40ndash1
00f
02ndash
1f30
ndash70f
50ndash1
00f
10ndash2
00f
--
-B
elgi
um (
Fla
nder
s)0
946
491
318
5617
022
--
Bel
gium
(W
allo
on)
210
050
150
100
200
--
-D
enm
ark
05
3040
05
1540
100
--
-F
inla
nd0
520
010
00
260
6015
0-
--
Fra
nce
215
010
01
5010
030
0-
--
Ger
man
y1
510
060
150
100
200
--
-G
reec
e1ndash
3-
50ndash1
401ndash
15
30ndash7
550
ndash300
150ndash
300
--
-Ir
elan
d1
-50
330
5015
0-
--
BIOSOLIDS MANAGEMENT 65
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
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L fil
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rom
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orig
inal
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er b
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not
fro
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al ty
pese
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file
s P
age
brea
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re tr
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the
orig
inal
lin
e le
ngth
s w
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brea
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tyle
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ther
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setti
ng-s
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how
ever
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grap
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iden
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rted
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ase
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t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Cd
Cr
Cu
Hg
Ni
Pb
Zn
As
Mo
Co
Dir
ecti
ve 8
627
8E
EC
(6lt
pHlt
7)1ndash
3-
50ndash1
401ndash
15
30ndash7
550
ndash300
150 ndash
300
--
-It
aly
15
-10
01
7510
030
0-
--
Lux
embo
urg
1ndash3
100ndash
200
50ndash1
401ndash
15
30ndash7
550
ndash 300
150ndash
300
--
-N
ethe
rlan
ds0
810
036
03
3585
140
--
-P
ortu
gal
-soi
l pH
lt5
51
5050
130
5015
0-
--
-55
lt s
oil p
H lt
73
200
100
15
7530
030
0-
--
-soi
l pH
gt7
430
020
02
110
450
450
--
-S
pain
-soi
l pH
lt7
110
050
130
5015
0-
--
-soi
l pH
gt7
315
021
01
511
230
045
0-
--
Sw
eden
04
6040
03
3040
100ndash
150
--
-U
nite
d K
ingd
om-5
lt s
oil p
H 5
53
-80
150
300
200
--
--5
5lt
soi
l pH
lt6
3-
100
160
300
250
-6`
soil
pH
`7
3-
135
175
300
300
-soi
l pH
gt7
3-
200
111
030
045
0E
ston
ia3
100
501
550
100
300
--
-L
atvi
a0
3ndash1
15ndash3
010
ndash25
01ndash
015
8ndash30
15ndash3
035
ndash100
--
-P
olan
d1ndash
350
ndash 100
25ndash 7
50
8ndash1
520
ndash 50
40ndash 8
080
ndash 180
--
-
BIOSOLIDS MANAGEMENT 66
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t th
is P
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file
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s ne
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l rep
rese
ntat
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rigin
al w
ork
has
been
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ompo
sed
from
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L fil
es c
reat
ed f
rom
the
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inal
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er b
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not
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m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
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inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
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nd o
ther
type
setti
ng-s
peci
fic fo
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ever
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grap
hic
erro
rs m
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ave
been
acc
iden
tally
inse
rted
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ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
a Low
er A
ustr
ia (
grad
e II
)b U
pper
Aus
tria
c B
urge
nlan
dd V
orar
lber
ge S
teie
rmar
kf C
arin
thia
A
bbre
viat
ions
As
ars
enic
Cd
cad
miu
m C
o c
obal
t C
r c
hrom
ium
Cu
cop
per
Hg
mer
cury
Mo
mol
ybde
num
Ni
nick
el P
b le
ad Z
n z
inc
Sour
ce A
dapt
ed f
rom
Eur
opea
n C
omm
unit
ies
2001
BIOSOLIDS MANAGEMENT 67
Abou
t th
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s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
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ompo
sed
from
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L fil
es c
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ed f
rom
the
orig
inal
pap
er b
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not
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heor
igin
al ty
pese
tting
file
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age
brea
ks a
re tr
ue to
the
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inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
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not b
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tain
ed a
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grap
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rs m
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Ple
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the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
bull was supported on the condition that additional quality controls and aninsurance fund be developed One party to the agreement (farmersrsquo union)asked for a ban on biosolids because current methods used are notconsidered sufficient to address the perceived risks related to theagricultural cycling of biosolids
bull In Finland and Luxembourg the farming community is generally hostiletoward the use of biosolids for land application mainly because of thepressure to use animal manure (eg the Finnish Union of AgriculturalProducers requested a ban on the use of biosolids for land application andhas renewed its stand against the use of biosolids in agriculture in 2001)
bull In Ireland and Portugal farmers tend to support the agricultural use ofbiosolids for economic and for agronomic (organic matter and phosphoruscontent) reasons although biosolids use in these countries has beenrelatively recent
bull In Spain Italy and Greece available information indicates that there islittle debate on use of biosolids
The analysis of stakeholdersrsquo positions (European Communities 2001)indicates that the main concerns on sewage sludge disposal and biosolidsrecycling are that the growing quantities of sewage sludge must be treated withthe aim of keeping both environmental and economic costs as low as possibleSimilarly improving practices of treatment and use of biosolids is nowconsidered essential Moreover within the context of uncertainties concerningthe potential impacts on human health and the environment of the variousdisposal and recycling options additional research is needed to increaseconfidence in the use of biosolids in agriculture
Some strategies suggested by the recent European Union biosolids-management assessment for reducing constraints and encouraging recycling ofbiosolids include the following (European Communities 2001)
bull Certify the treatment process involved the quality of biosolids andrecycling practices
bull Develop a trust fund or insurance system to cover any loss of profitsdamages or other costs related to the use of biosolids in agriculturetogether with legal provisions to regulate producer liability
bull Standardize science-based laws and regulationsbull Enhance mutual confidence and communication and transfer of
information between stakeholders
BIOSOLIDS MANAGEMENT 68
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t th
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file
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s ne
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igita
l rep
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ntat
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he o
rigin
al w
ork
has
been
rec
ompo
sed
from
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L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
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m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
bull Diminish uncertainty over risks to human health and environment andextend the assessment and dissemination of information beyond heavymetals to include organic pollutants and pathogens
bull Develop codes of practice for the recycling of biosolids the possible useof labels for quality assurance and associated training programs andoutreach activities for stakeholders
When European Union biosolids-management practices are compared withthose of the US it is apparent that European and US contaminant limits applylargely to heavy metals and are based on (1) the concentration of the biosolidsitself (2) the loading or total amount of metal that can be added and howquickly it can be applied and (3) the maximum concentration of metals in soilallowed to build up after biosolids application
According to an analysis of regulations in the United States and someEuropean countries by McGrath et al (1994) three basic approaches to settinglimits were distinguished (1) analyzing the pathways of pollutant transfer toselected target organisms and an assessment of the likely harmful effects thatmetals might have on the target (2) setting limits consistent with the lowest-observed-adverse-effect concentrations which are actual cases of effects due tometals but not necessarily derived from studies that involved applications ofbiosolids and (3) attempting to match the metal inputs to soils to the smalllosses of metals due to crop removal soil erosion and leaching (metal balanceapproach) These approaches were considered responsible for the widelydifferent numerical limits for metals arising either from a policy decision toreach zero impact (metals balance) and associated low levels or fromapproaches that allow some increase in metal concentrations in soils based ontarget organisms and use of associated models and sparse toxicity data Thusthe practice of implementing vastly different regulations for biosolidsapplication to land in the United States and within European Union membernations create differing social economic technological and environmentalimpacts that beg consensus resolution in the scientific technical and regulatorycommunities
Within the European Union the intended goal and most widely appliedbiosolids disposition option is agricultural use However the selection of anoption and its implementation according to European Commission directives isaffected by local or national circumstances Thus the degree of flexibilityvaries Some indication of the production and disposal of domestic sewagesludge and biosolids in Europe as of 1992 is included in Table 2ndash10 Notablyocean disposal has been phased out so that the principal disposal options nowinclude agricultural use landfill and incineration As in the United States the
BIOSOLIDS MANAGEMENT 69
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t th
is P
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file
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s ne
w d
igita
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ntat
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rigin
al w
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ompo
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inal
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igin
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age
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ks a
re tr
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inal
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e le
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s w
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brea
ks h
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tyle
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ther
type
setti
ng-s
peci
fic fo
rmat
ting
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ever
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tain
ed a
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ome
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grap
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icat
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as th
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TA
BL
E 2
ndash10
Pro
duct
ion
and
Dis
posa
l of
Dom
esti
c S
ewag
e S
ludg
e an
d B
ioso
lids
in E
urop
ean
Com
mun
ity
in 1
992
(10
00 m
etri
c to
ns o
f dr
y m
atte
r pe
rye
ar [
])
Mem
ber
Sta
teQ
uant
ity
Agr
icul
ture
Lan
dfil
lIn
cine
ratio
nO
cean
Oth
era
Aus
tria
170
(23
)30
6 (
18)
595
(35
)57
8 (
34)
-22
1 (
13)
Bel
gium
592
(0
8)17
2 (
29)
325
(55
)8
9 (1
5)-
06
(1)
Den
mar
k17
03
(23
)92
(54
)34
(54
)40
9 (
24)
-3
4 (2
)F
inla
nd15
0 (2
0)
375
(25
)11
25
(75)
--
-F
ranc
e86
54
(12
0)50
2 (5
8)23
35
(27)
130
(15)
--
Ger
man
y2
681
2 (2
3)
724
(27)
144
8 (5
4)37
52
(14)
-13
4 (5
)U
nite
d K
ingd
om1
107
(15
0)48
8 (4
4)88
6 (
8)77
4 (
7)32
2 (3
0)12
1 (1
1)G
reec
e48
21b
(06
)4
8 (1
0)43
4 (
90)
--
-Ir
elan
d36
7 (
05)
44
(12)
166
(45
)-
128
(35
)2
9 (8
)It
aly
816
(11
0)26
92
(33)
449
(55)
162
(2)
-81
6 (
10)
Lux
embo
urg
8 (0
1)
1(12
)7
(88)
--
-N
ethe
rlan
ds33
5 (4
5)
87 (
26)
171
(51)
10 (
3)-
67 (
20)
Nor
way
95 (
13)
532
(58
)41
8 (
44)
--
-P
ortu
gal
25 (
03)
27
(11)
73
(29)
-0
5 (2
)14
5 (
58)c
Spa
in35
0 (4
7)
175
(5)
122
5 (3
5)17
5 (
5)35
(10
)-
BIOSOLIDS MANAGEMENT 70
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t th
is P
DF
file
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s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
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inal
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igin
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age
brea
ks a
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inal
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brea
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ther
type
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ng-s
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fic fo
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not b
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grap
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ay h
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Ple
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of t
his
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icat
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as th
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ibut
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Sw
eden
200
(27
)80
(40
)12
0 (6
0)-
--
Sw
itze
rlan
d27
0 (3
6)
121
5 (4
5)81
(30
)67
5 (
25)
--
Tot
al7
387
(100
0)
269
01
(36
4)3
066
2 (4
16)
801
4 (1
09)
380
3 (5
19)
447
1 (6
)a R
ecul
tiva
tion
for
estr
y a
nd s
o fo
rth
b Oth
er e
stim
ates
at 2
000
00 m
etri
c to
ns o
f dr
y m
atte
r per
yea
rc S
urfa
ce w
ater
So
urce
Ada
pted
fro
m M
atth
ews
1996
BIOSOLIDS MANAGEMENT 71
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setti
ng-s
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not b
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typo
grap
hic
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rs m
ay h
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been
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Ple
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use
the
prin
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sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
European Commission has developed regulatory limits (Sewage SludgeDirective 86278EEC) when biosolids are used in agriculture The SewageSludge Directive requires member states to apply maximum limit values forcertain heavy metals in the biosolids and in the soil to which it is applied topretreat sewage sludge and to restrict its use including the frequency andquantity of application on certain soils
These regulations establish conditions relating to pretreatment nutrientneeds quality of soil protection of surface waters and groundwaters andcompliance with concentration limits of heavy metals in soil Use of biosolids isprohibited on specified categories of land within defined periods prior toharvesting and where concentrations of heavy metals in the soil exceedspecified limit values Records must be kept and made available to thecompetent authorities on the quantities composition use treatment and resultsof analysis on biosolids the names and addresses of recipients of biosolids andthe places where biosolids are to be used (European Union 2000a)Accordingly member states have performed biosolids surveys to comply withthe reporting requirements such as the UK Sludge Survey for 1996ndash1997(Gendebien et al 1999) Summary reports indicating biosolids quality andultimate disposition quantities are to be submitted to the European Union every5 years (eg UK Department of the Environment 1993)
A part of the implementation of the directive is that application forbiosolids use is made in advance of the operation and conditions are applied tothe methods and type of biosolids used Consideration is given to the linksbetween biosolids use and potential transmission of pathogens to the humanfood chain and into water courses or supplies through nutrient leaching Inaddition biosolids producers are obliged to provide details of biosolidscomposition to owners of land where biosolids will be applied (see Box 2ndash1)Analytical methods sampling frequencies monitoring procedures and record-keeping requirements are also prescribed (see Box 2ndash2)
Proposed revisions are included in the European Union WorkingDocument on Sludge (European Union 2000b) and changes in limit values arebeing considered for heavy metals and organic compounds on the basis ofbiosolids concentrations and soil characteristics The use of biosolids in soilswhere the concentrations of heavy metals exceed the limit values suggested inTable 2ndash11 would be allowed only on a case-specific basis and member stateswould have to ensure that those limit values are not exceeded as a result of theuse of biosolids If the concentrations of one or more heavy metals in biosolidsare higher than the concentration limits suggested in Table 2ndash4 or if theconcentrations of one or more organic compounds in biosolids are higher thanthe concentration limits proposed in Table 2ndash12 the use of biosolids
BIOSOLIDS MANAGEMENT 72
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al w
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ompo
sed
from
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inal
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not
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tting
file
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brea
ks a
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inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
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tain
ed a
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grap
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Ple
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sion
of t
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icat
ion
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thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
BOX 2ndash1 EXAMPLES OF REGULATORY CONTROLS
One European Union member state (United Kingdom) operates aprenotification system through its competent authority This system isdesigned to ensure that biosolids are given suitable treatment beforespreading on agricultural land and has led to the setting of legal limits formetals in soil according to the requirements of the directive In additionthe UK has set limits for 10-y average rates of application for metals inbiosolids and requires that producers identify suitable sites A code ofpractice for the agricultural use of biosolids in agriculture has been issuedand there is a separate code dealing with the agricultural use of biosolidsin forests The responsibility for undertaking sampling and analysis lieswith the biosolids producers who must support their activities bymaintaining records and supplying data to the Environment MinistrySampling and analytical procedures are in accordance with the code ofpractice which incorporates the directiversquos requirements and specifiesrestrictions to minimize risks to health
The Sewage Sludge Directive has been incorporated into thelegislation of another member state (Sweden) through an order issued bythe Environment Ministry This order governs the monitoring of biosolidsquality and the spreading of biosolids on arable land It also lays downlimit values for inputs of nutrients to arable soil via biosolids limit valuesfor metals in arable soils and limit values for inputs of metals to arablesoil A separate ordinance specifies limit values for metal concentrationsin biosolids intended for agricultural use Biosolids must be treated beforebeing used in agriculture and producers of biosolids must supply adeclaration of contents to those who will use the biosolids Similarly theoperation of sewage plants in that state requires authorization fromnational and regional authorities
In a third member state (Portugal) the national law sets limit valuesfor heavy metal concentrations in the soil and the quantity of biosolids perhectare
Source Adapted from European Union 2000a
should not take place Compliance with Tables 2ndash4 and 2ndash12 is assumed if90 of samples in a 12-month period are less than the standards and if 10 ofsamples exceed the standards by less than 50 The maximum annualquantities of heavy metals indicated in Table 2ndash6 that may be added to the soilbecause of use of biosolids should not be exceeded These limit values areintended to be reviewed every 6 years with a view toward achieving medium-and long-term concentrations for pollution prevention
BIOSOLIDS MANAGEMENT 73
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ompo
sed
from
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inal
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the
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inal
lin
e le
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s w
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brea
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ng s
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s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
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rs m
ay h
ave
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Ple
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the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
BOX 2ndash2 EXAMPLES OF MONITORING PROCEDURES
In one member state (United Kingdom) monitoring is undertaken inaccordance with the directive whereby soil is analyzed on first applicationand at least every twentieth year while biosolids are spread to determineits pH and metals levels Biosolids are analyzed at least every six monthsand every time significant changes occur in the quality of the biosolidstreated at the works Analysis is the responsibility of the biosolidsproducer but records must be kept and made available to the EnvironmentMinistry The analytical methods used are in accordance with thedirective The parameters analyzed conform to the directive and there area number of additional ones
In another member state (Portugal) the national law requiressampling of both the biosolids and the soil The biosolids are analysed bythe user who has the burden of proof that it complies with the legallyestablished limits The results are then made available to the Institute ofWaste (INR) Regional Directorates of the Environment (DRAs) orGeneral Inspectorate of Environment (IGA) who give the final approvalThe analyses of the soil are to be undertaken before biosolids are appliedalthough there is no specification of sampling frequency after the biosolidsare spread The results must be kept for five years
In another member state (Sweden) the producer of biosolids isresponsible for carrying out sampling and analysis of biosolids in respectof dry matter and loss on ignition pH total phosphorus total nitrogenammonium nitrogen lead cadmium copper chromium mercury nickeland zinc The order that requires this also lays down detailed rules onsampling and analysis methods The frequency of sampling and analysisis determined according to the treatment capacity of the plant As aminimum the sampling and analysis must be done on an annual basisPermitting authorities are responsible for supervision and inspection
Source Adapted from European Union 2000a
PATHOGEN ISSUES AND TREATMENT CONTROLS
EPA sponsored the Workshop on Emerging Infectious Disease Agents andIssues Associated with Animal Manures Biosolids and Other Similar By-Products in Cincinnati Ohio in June 2001 This workshop was attended byover 100 participants from around the world who raised general concerns withrespect to bacteria viruses and parasites in these materials Although animalmanures are generally land applied and untreated and contain pathogens ofconcern only biosolids are addressed in this report Concerns for pathogencontrol in Classes A and B biosolids were expressed For example becauseClass B biosolids are only partially disinfected through treatment
BIOSOLIDS MANAGEMENT 74
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TABLE 2ndash11 European Union Limit Values for Concentrations of Heavy Metals inSoil
Limit Values (mgkg of DM)Elements Directive
86278EEC6ltpHlt7
Proposed5`pHlt6
Proposed6`pHlt7
ProposedpH`7
Cadmium 1ndash3 05 1 15Chromium - 30 60 100Copper 50ndash140 20 50 100Mercury 1ndash15 01 05 1Nickel 30ndash75 15 50 70Lead 50ndash300 70 70 100Zinc 150ndash300 60 150 200
Note When the concentration value of an element in a specific land area is higher than theconcentration limit set in the table the competent authority may still allow the use of biosolids onthat land on a case-by-case basis after evaluation of the following aspects (1) intake of heavymetals by animals (2) uptake of heavy metals by plants (3) groundwater contamination and (4)long-term effects on biodiversity particularly on soil biota The areas of land with higher metalconcentrations will be monitored and the possibility of using biosolids will be subject to a periodicalassessment by the competent authorityAbbreviation DM dry matterSource Adapted from European Union 2000b
further disinfection of land-applied Class B biosolids is related tomanagement and treatment by natural attenuation Workshop participantsagreed that more data are needed on rates of pathogen survival in soil or oncrops after application of biosolids As discussed earlier the criteria of at leastseven samples with a geometric mean of less than 2times106 MPN or CPU of fecalcoliform per gram of dry weight as a control is one of the means fordetermining Class B treatment adequacy Better documentation is needed tocorrelate that or any number to treatment efficiency
The process control requirements for Classes A and B designations areessentially identical to those established in 40 CFR 257 the 1979 regulationspreceding 40 CFR 503 The treatment controls were based on an assumed logreduction of at least 1 for each option (EPA 1985 1989) The fecal densityrequirement established in 40 CFR 503 was assumed to correlate to a roughly 2-log reduction (EPA 1985 1992) However as early as 1981 it was recognizedthat additional research was necessary to better document the presence ofpathogens and other organisms in raw sewage sludge and their
BIOSOLIDS MANAGEMENT 75
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TABLE 2ndash12 Proposed Limit Values for Concentrations of Organic Compounds andDioxins in Biosolids for Use on LandOrganic Compounds Proposed Limit Values (mgkg of DM)AOXa 500LASb 2600DEHPc 100NPEd 50PAHe 6PCBf 08Dioxins Proposed Limit Values (ng TEkg of DM)PCDDPCKFg 100
aSum of halogenated organic compoundsbLinear alkylbenzene sulfonatescDi(2-ethylhexyl)phthalatedIt comprises the substances nonylphenol and nonylphenolethoxylates with 1 or 2 ethoxy groupseSum of the following polycyclic aromatic hydrocarbons acenapthene phenanthrene fluoreneflouranthene pyrene benzo[b+j+k]fluoranthene benzo[a]pyrene benzo-[ghi]perylene indeno[123-cd]pyrenefSum of the polychlorinated biphenyl congeners number 28 52 101 118 138 153 180gPolychlorinated dibenzodioxins and dibenzofuransAbbreviations DM dry matter TE 2378-tetrachloro-p-dioxin toxicity equivalentsSource Adapted from European Union 2000b
fate through the various treatment regimes in the regulations and acomprehensive literature review of all relevant publications between 1940 and1980 was conducted (Pedersen 1981)
Based on limited analyses in EPArsquos National Risk Management ResearchLaboratory (NRMRL) in Cincinnati and more complete data collected inWisconsin between 1998 and 2000 fecal coliforms appear to be present at verylow densities in biosolids and perhaps even in raw sewage sludge That is alsotrue of Ascaris eggs and enteric virus (JSmith EPA personal communication2002 WDNR unpublished data 2000) These data raise the question of thevalidity of relying on numeric standards for various organisms because it isunclear what they represent For example enteric virus and helminth ova areused to measure treatment efficiency for Class A biosolids because of theirhardiness and resistance to treatment but they are also used as indicators ofClass A treatment in alternatives 3 and 4 (discussed previ
BIOSOLIDS MANAGEMENT 76
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ously) Thus numeric standards are not necessarily incorrect but there is a needto better define their regulatory meaning and adequacy Another point ofconcern raised at the EPA workshop was assay development For example withthe measurement of Ascaris there is no proper protocol for samplingpretreatment and purification before the assay and the appropriate quality-assurance and quality-control (QA and QC) protocols for the spike to be used inthe assays The assays for the other parasites and protozoan oocysts are alsounreliable and underdeveloped The analytical methods for other parasitesprotozoan oocysts and even fecal coliform in biosolids are also suspect andmethod development and validation are needed (EPA 2001c) Table 2ndash13provides a partial list of possible organisms that may be used as measures oftreatment efficiency and that was discussed at the EPA 2001 conference
Many organisms of concern have been known to be present in sewagesludge and regulations have been developed with the intent to maximize theirelimination and minimize the potential transport to humans This was evident inthe initial sewage sludge (40 CFR 257) regulations promulgated in 1979Nevertheless new organisms of concern have been identified and new researchshould be initiated to reconfirm the level of disinfection achieved throughvarious pathogen process controls Bacteria such as E coli 0157H7 Listeriaand Helicobacter have emerged as potential public-health problems (seeChapter 6 for more details) Table 2ndash14 lists these and other bacteria ofpotential regulatory concern including ones that represent a change in concernfrom low to high or are newly recognized In addition it is necessary tounderstand the mechanisms responsible for pathogen reduction and timerequired to meet the control-process requirements For these reasons it isnecessary to validate the rate of elimination of pathogens through varioustreatment regimes Research in this area is currently underway (JSmith EPApersonal communication May 2002)
In the area of virology the conference raised several issues concerningviruses such as coxsackievirus echovirus adenoviruses rotaviruses andreovirus (to name a few) Their potential impact on public health is included inTable 2ndash15 For pathogen monitoring the virologists discussed usingenteroviruses and coliphages for process disinfection efficacy but suggested Ecoli fecal coliforms enterococci and Clostridium perfringens for fieldmonitoring As a result of the workshop deliberations the consensus opinion ofthe participating virologists was that Class-B-treatment processes should yieldthe reductions summarized in Table 2ndash16 if the processes are properlyconducted and maintained and the sitersquos climate geology and soilcharacteristics enable natural attenuation
Regarding the assessment of helminth eggs and protozoan oocysts theefficacy of existing Class B disinfection processes for inactivating parasites
BIOSOLIDS MANAGEMENT 77
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TABLE 2ndash13 Process Criteria for Class B Biosolids
Bacterial InactivationProcess Temperature Critical
ParameterTime Possible
Measure ofEfficiency
Air drying gt0degC Desiccation by-products
2ndash3 mo E coli fecalcoliformClostridium perfringens
Alkalinestabilization
Ambient Ammonia pH 2 h Clostridium perfringens
Aerobicdigestion
15ndash20degC Endogenousmicrobialactivity
60ndash40 d Fecal coliformE coli
Anaerobicdigestion
20ndash35degC Endogenousmicrobialactivityorganic by-products
60ndash15 d Clostridium perfringens
Composting 40ndash55degC Organic by-products
5 d at40degC 4h at 55degC
Clostridium perfringens
Source EPA 2001c
remains a concern but the processes should be effective for protozoanoocysts However little information is available on treatment efficiency ofhelminth eggs There are also concerns with analytical methods for thedetection and identification of helminth eggs of the species noted in Table 2ndash17Therefore research is needed to develop reliable assays to measure helmintheggs and to assess the efficacy of Class B processes for inactivating helminths(eg Taenia and Toxicara) where fecal coliforms have traditionally been theonly means of monitoring pathogen-inactivation performance The workshopparticipants expressed interest in using Clostridium perfringens as an indicatororganism when noncharged biocides are the major agent for inactivation and foranaerobic digestion lagoon storage composting and alkaline stabilization Theexisting Part 503 regulation states that the Class A disinfected biosolids are farless a concern as a result of Ascaris egg controls along with the temperaturefactors In the current Class A requirements monitoring is required forSalmonella or fecal coliform in addition to meeting one of several treatmentcontrol processes which include several nationally approved processesdesignated equivalent to a process to further reduce pathogens (PFRP) (listed inTable 2ndash18)
BIOSOLIDS MANAGEMENT 78
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TABLE 2ndash14 Bacterial Pathogens of Potential Concern in Biosolids
Major ConcernmdashClassica New IssuesmdashChangesb
Salmonella E coli 0157H7Shigella ListeriaEnteropathogenic E coli HelicobacterYersinia enterocolitica MycobacteriaCampylobacter jejuni AeromonasVibrio cholera LegionellaLeptospira Burkholderia
EndotoxinsAntibiotic resistance
aKowal 1985bEPA 2001c
Concerns for Class A processes were also elucidated at the EPA workshopHowever there was less concern with pathogen contamination and more withthe confirmation of the efficiency of Class A processes (Approved mechanismsof pathogen control for Class A treatment for bacteria viruses and parasites aresummarized in Table 2ndash19) Issues of concern included regrowth of pathogenswith short-term stabilized biosolids and possible emission of odors Others werespecification of treatment process versus product control and the appropriatepoint in the treatment process to obtain pre-treatment samples and whether touse an indicator organism to predict pathogen survival and recontaminationHowever the major problem discussed at the workshop was the Class Aprocess criteria that do not take into account potentials for regrowth Regrowthof pathogens can occur in Class A biosolids but generally not in Class Bbiosolids To prevent pathogen regrowth a fairly stable background populationof microorganisms is needed Relevant research on composting indicates theneed for 104 to 105 microorganisms per gram of dry weight of solid (Burnhamet al 1992) With such background levels as would be common with Class Bbiosolids pathogen regrowth is inhibited by competition with the existingmicrobial ecosystem Class A disinfection processes generally eliminate thesecompeting microorganisms requiring retesting of Class A biosolids if used inbulk quantities more than 3 weeks or so after production
Bioaerosol generation is a concern with the processes of aerobic digestionanaerobic digestion composting alkaline stabilization and combinations The
BIOSOLIDS MANAGEMENT 79
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concerns are bacterial species viruses and bacteria in bioaerosols but probablynot parasites due to their greater size and weight
TABLE 2ndash15 Principal Viruses of Concern in Municipal Wastewater and SewageSludgeVirus Diseases of Public Health ConcernPoliovirus PoliomyelitisCoxsackievirus Meningitis pneumonia hepatitis fever etcEchovirus Meningitis paralysis encephalitis fever etcHepatitis A virus Infectious hepatitisRotavirus Acute gastroenteritis with sever diarrheaNorwalk agents Epidemic gastroenteritis with severe diarrheaReovirus Respiratory infections gastroenteritis
Source Kowal 1985
In summary several pathogen-related issues and research needs wereidentified at the EPA workshop and in related literature
bull Further information regarding pathogen survival in processing or emissionduring the process
bull Research on vectors carrying pathogens and toxinsbull Assessment of bioaerosols and other chemical aerosolsbull Test-method development and validation for various organisms in sewage
sludge and biosolidsbull Field verification of efficacy of Class A and Class B treatment processes
(including data to directly relate process controls to initial and finalpathogen and indicator densities)
bull Development of indicator pathogens for assessment of impact andattenuation in field situations
PATHOGEN EQUIVALENCY COMMITTEE
A critical function in the regulation of sewage sludge and biosolids isfulfilled by the Pathogen Equivalency Committee (PEC) established in 1985The PEC is composed of experts within EPA who evaluate treatmenttechnologies to determine whether they are equivalent in treatment efficiency toeither recognized PSRP (Class B) or PFRP (Class A) as defined in 40 CFR
BIOSOLIDS MANAGEMENT 80
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TABLE 2ndash16 Class B Virus Reduction for Biosolids Disinfection Process
Process Virus Log Reduction TimeLagoon storage 1ndash2 6ndash12 moMesophilic anaerobic digestion 1ndash2 15ndash30 dMesophilic aerobic digestion 1ndash2 15ndash30 dAlkaline stabilizationpH=11 to 12
1ndash3 1 d
Air drying lt3 solids lt1 2ndash3 moAir drying gt3 solids 3ndash4 2ndash3 moHeat drying 55ndash60degC 3ndash4 ~1 hComposting 40ndash55degC 3ndash4 6 wk
Source EPA 2001c
503 Determination of several such treatment technologies expected withina few years are vermicomposting microwave technology infrared irradiationtechnology alkaline stabilization anaerobic digestion and aerobic digestionThe equivalency criteria could be related to treatment alternatives 1 through 6for Class A or alternatives 1 through 3 for Class B
The long-term responsibilities of PEC include integrating and developingmethods for microbial assays gross biosolids parameters analysis of metalsand analytical techniques for organics many of which are included in Standard Methods manuals published by the American Society for Testing andMaterials and agricultural analyses In developing microbial assays protocoldevelopment and workshops to train EPA and other professionals are neededThe same issues relate to vector-attraction tests which need to be compiled andrefined for new stabilization techniques Due to the major problems arising withmanure in nonpoint source pollution USDA and EPA should collaborate onmethod development However EPA does not have a formal coordinated groupthat handles these important issues and there has been no logical protocol toresolve these questions Even so the committee believes that this ongoingproblem could be resolved with appropriate action from EPA
In the fall of 2000 Haas (2001) conducted an independent assessment ofthe pathogen equivalency process That report focused on the determination ofequivalency for both PSRP and PFRP process assessment Overall the reportfound that the members of the PEC need assistance to better conduct theirduties The reportrsquos short-term recommendations to support the PEC were asfollow
BIOSOLIDS MANAGEMENT 81
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TABLE 2ndash17 Principal Parasites of Concern in Municipal Wastewater and SewageSludgeHelminth Worms Symptoms or DiseasesAscaris lumbricoides Digestive disturbances abdominal painAscaris suum Coughing chest pain or asymptomaticTrichuris trichiura Abdominal pain diarrhea anemia weight lossToxocara canis Fever abdominal discomfort and muscle achesTaenia sasginata Nervousness insomnia anorexiaTaenia solium Nervousness insomnia anorexiaNecator americanus Hookworm diseaseHymenolepis nana Taeniasis
Source Kowal 1985
bull The PEC members should have a formal portion of their time allocated toPEC responsibilities
bull Travel funds should be put at the disposal of the PEC to enable meetingattendance and visits to selected sites of petitioners
bull There is a perception on the part of PEC members that EPArsquos Cincinnatilaboratories do not include biosolids as a formal part of their missionstatement This needs to be clarified and rectified
bull A formal procedure for designation of backup members should be devised
The report also included a protocol for formally handling a PECapplication and recommended that it be developed via a formal approval routeOverall the report found that the diverse background of EPA staff serving onthe PEC is a well-rounded forum and should be continued
IMPLEMENTATION AND END-USE PRACTICES
Overview
There are three major alternatives for final disposition of sewage sludge(1) recycling as biosolids to agricultural land as a fertilizer or soil amendmentor selling or giving away to the public for use on home gardens or lawns (2)
BIOSOLIDS MANAGEMENT 82
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TABLE 2ndash18 Processes Recommended as Equivalent to PFRP
Process Criteria for ApprovalCBI Walker IncAurora Illinois
Two-stage aerobic digestion processutilized time-temperature control withresulting mesophilic aerobic digestion forstabilization
Fuchs Gass and WasserteckinkMayen Germany
Two-stage autothermophilic aerobicdigestion process utilizing time-temperature control with resultingmesophilic aerobic digestion forstabilization
International Process Systems IncGlastonbay Connecticut
In-vessel composting process related totime-temperature disinfection followed bycompost maturation for stabilization
K-F Environmental Technologies IncPompton Plains New Jersey
Indirect drying process utilizing the PSRP(process to significantly reduce pathogens)heat drying process criteria and short-termstabilization at less than 10 moisturecontent
Lyonnaise des EauxPecz-Sur-Seine France
Two-phase thermophillic and mesophilicanaerobic digestion where pathogencriteria used to demonstrate PFRP(process for the further reduction ofpathogens) criteria with mesophilicstabilization
AJW IncSanta Barbara California
Thermophilic alkaline stabilization usedpasteurization criteria with short-termstabilization related by pH
N-ViroToledo Ohio
Advance alkaline stabilization that hasvarious alternatives for disinfection andalkaline composting for disinfection Theyused the pathogen criteria and alternative 2
Synox CorporationJacksonville Floride
OxyOzonation process is an acid-oxidizing process that utilizes a pathogencriteria from influent and effluent inalternative 3
Ultra Clear IncMarlboro New Jersey
Microbiological composting and dryingprocess which is a time-temperatureprocess equivalency
Source EPA 1999b
BIOSOLIDS MANAGEMENT 83
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heor
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age
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ue to
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inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
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ay h
ave
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rted
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ase
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ibut
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TABLE 2ndash19 Class A Inactivation of Pathogens
Process Inactivation ConcernsAerobic digestion(thermophilic)
Time temperature Oxygen transfer solidscontent bioaerosols
Anaerobic digestion(thermophilic)
By-products timetemperature
Solids content odorbioaerosols pH
Composting(thermophilic)
By Products timetemperature
Solids content odorbioaerosols pH
Alkaline stabilization Ammonia time-temperature Solids content odoraerosols pH
Heat drying(gt80degC)
Time-temperature Explosions odors aerosols
Irradiation(gamma beta)
gt1 megarad Solids content stablization
CombinationsDigestorsLagoonsDrying beds
Time-temperature by-products
Solids content odorsbioaerosols
Sources Reimers et al 1986ab 1999 2001 EPA 2001c
burying in a municipal solid-waste landfill or a surface disposal site or (3)burning in an incinerator When assessing any of these practices they should beevaluated holistically for risk For instance if all land application should ceasehow would the overall risk be altered if additional landfills surface disposalsites and incinerators were constructed and operated to accommodate theadditional volumes In response to EPArsquos beneficial-use policy the publicationof risk-based regulations and the general trend toward recycling numerousstates began to encourage POTWs to use their biosolids in the late 1980s and1990s This policy was further aided by philosophical shifts away from andpolitical and legal difficulties associated with siting and constructingincinerators and landfills
Management Practices
Biosolids are applied to land through one of three methods
bull Injection Injection vehicles directly inject liquid biosolids at a depth of 6to 9 inches into the soil The injectors may simultaneously disc the field
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ng-s
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or include fine injection tubes for minimal soil breakup depending on thetype of farm-management practices used This method is considered themost effective for odor control and minimizes the risk of runoff to surfacewaters However it is not possible to use injection when applying to haycrops or frozen ground Application is usually prior to planting or afterharvest Vehicles range from 1500- to 5000-gallon capacity Injection isconsidered a physical-barrier option for satisfying vector-controlrequirements
bull Incorporation Biosolids are applied to the surface of the soil and thenphysically worked into the field within 6 h or as specified by the permitauthority This method is common for cake solids that cannot be injectedand is used either prior to planting or after harvest Biosolids are generallyincorporated at a depth of 6 to 9 inches Incorporation is also considered aphysical-barrier option for satisfying vector-control requirements
bull Surface Application Either liquid or cake solids are applied to the soilsurface but are not incorporated into the soil until normal farmingpractices disturb the soil This method is common for hay crops andapplication during winter months Surface application does not satisfyvector-control requirements and stabilization must be accomplishedthrough treatment prior to surface application
The federal regulations for managing a land-application site include thefollowing prescriptions
bull Biosolids shall not be applied to land if it is likely to adversely affect athreatened or endangered species or its critical habitat
bull Biosolids must not be applied to land that is frozen flooded or snowcovered so that biosolids cannot enter any wetland or waters of theUnited States except as provided in an National Pollutant DischargeElimination System (NPDES) permit
bull Biosolids must not be applied to land at a distance of less than 10 meters(33 feet) from any waters of the United States unless otherwise specifiedin a NPDES permit
bull Biosolids must be applied at a rate equal to or less than the agronomicnitrogen need of the crop to be grown
Some states require more stringent site criteria including greater distancesfrom surface waters maximum slope restrictions minimum depths togroundwater and bedrock minimum and maximum soil permeability ratesminimum distances to residences or recreation areas and minimum distances toprivate or public water-supply wells For example Table 2ndash20 compares thecriteria required by Wisconsin with those of the Part 503 rule
BIOSOLIDS MANAGEMENT 85
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as th
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TA
BL
E 2
ndash20
Wis
cons
in R
equi
rem
ents
for
Bio
soli
ds A
ppli
ed to
the
Lan
d in
Bul
k
Sit
e C
rite
ria
Sur
face
Inco
rpor
atio
nIn
ject
ion
Par
t 503
Req
uire
men
tsD
epth
to b
edro
ck3
ft3
ft3
ftD
epth
to h
igh
grou
ndw
ater
3 ft
3 ft
3 ft
All
owab
le s
lope
s0ndash
60ndash
12
0ndash12
D
ista
nce
to w
ells
- C
omm
unit
y w
ater
sup
ply
or s
choo
l10
00 f
t10
00 f
t10
00 f
t-
Oth
era
250
ft25
0 ft
a25
0 ft
a
Min
imum
dis
tanc
e to
res
iden
ce b
usin
ess
or r
ecre
atio
n ar
ea50
0 ft
200
ft20
0 ft
Min
imum
dis
tanc
e to
res
iden
ce o
r bu
sine
ss w
ith
perm
issi
on25
0 ft
100
ft10
0 ft
Dis
tanc
e to
rur
al s
choo
ls a
nd h
ealth
car
e fa
cilit
ies
1000
ft
1000
ft
500
ftD
ista
nce
to p
rope
rty
line
50 f
tb25
ftb
25 f
tb
Min
imum
dis
tanc
e to
str
eam
s la
kes
pon
ds w
etla
nds
or
chan
neli
zed
wat
erw
ays
conn
ecte
d to
a s
trea
m l
ake
or
wet
land
33 f
t
- S
lope
0 to
lt6
20
0 ft
150
ft10
0 ft
BIOSOLIDS MANAGEMENT 86
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- S
lope
6 to
lt12
N
ot a
llow
ed20
0 ft
150
ftM
inim
um d
ista
nce
to g
rass
wat
erw
ays
or
dry
run
wit
h a
50 f
t ran
ge g
rass
str
ipc
- S
lope
0 to
lt6
10
0 ft
50 f
t25
ft
- S
lope
6 to
lt12
N
ot a
llow
ed10
0 ft
50 f
tS
oil p
erm
eabi
lity
ran
ge (
inh
)0
2ndash6
00ndash
60
0ndash6
0a S
epar
atio
n di
stan
ces
to n
onpo
tabl
e w
ells
use
d fo
r ir
riga
tion
or
mon
itor
ing
may
be
redu
ced
to 5
0 ft
if
the
bios
olid
s ar
e in
corp
orat
ed o
r in
ject
ed a
nd th
e de
part
men
t doe
s no
tde
term
ine
that
a g
reat
er d
ista
nce
to th
e w
ells
is r
equi
red
to p
rote
ct th
e gr
ound
wat
er
b The
dis
tanc
es to
pro
pert
y li
nes
may
be
redu
ced
wit
h th
e w
ritt
en p
erm
issi
on o
f bo
th p
rope
rty
owne
rs
c Rep
arat
ion
dist
ance
s no
t req
uire
d if
gra
ss w
ater
way
or
dry
run
wit
h gr
ass
stri
p is
con
tain
ed w
ithi
n a
site
or
fiel
d fo
r th
e pu
rpos
e of
ero
sion
con
trol
So
urce
Ada
pted
fro
m W
isco
nsin
Adm
inis
trat
ive
Cod
e 19
96
BIOSOLIDS MANAGEMENT 87
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Inherent in the concept of developing two classes of pathogen-controlcriteria are management-practices and site-restriction requirements to equalizethe two standards EPA imposed limitations regarding minimum time durationsbetween application of Class B biosolids and the harvesting of certain crops thegrazing of animals and public access to the site Those limitations aresummarized in Table 2ndash21 If the limitations are followed EPA concluded thatthe level of protection from pathogenic organisms in Class B biosolids wasequal to the protection provided by the unregulated use of Class A biosolids
Three factors affect the potential dietary exposure to pathogens via cropsthrough land application (EPA 1999b) (1) pathogens must be in the biosolids(2) the application of biosolids to food crops must transfer the pathogens to theharvested crop and (3) the crop must be ingested before it is processed toreduce the pathogens If all three factors are not present potential exposure iseliminated The production of Class A biosolids reduces the pathogens inbiosolids to below detectable concentrations and may be used without furtherrestriction if it is also deemed exceptional quality (EQ) In contrast Class Bbiosolids may contain reduced but still measurable densities of pathogenicbacteria viruses protozoans and viable helminth ova
The site restrictions are imposed to allow for further reduction of thepathogenic populations through natural attenuation processes The restrictionsare based primarily on the survival rate of helminth ova which are consideredthe hardiest pathogens that might be present in biosolids Some of the factorsthat influence pathogen survival are sunlight moisture pH temperaturecations presence of soil microflora and organic material content Potentialpathways of exposure are also considered in setting the time restrictions Forinstance pathogen die-off is much different when crops are exposed on theirsurfaces compared with crops grown underground Helminth ova can survive ontop of soil or within soil for months to years depending on climate thus longerwaiting periods are required for food crops either grown in the biosolids-amended soil or in contact with the soil-biosolids mixture In practice far lessthan 1 of biosolids-amended land is used for the production of unprocessedfood-chain crops (WDNR unpublished data 2001) Of 27 states responding toan inquiry on this topic by the Wisconsin Department of Natural Resources(WDNR) 25 reported no such use and two reported less than 1 such useBased on these results this finding can be reasonably expected in the remaining23 states
Other management practices are intended to minimize the introduction ofbiosolids to surface water (primarily because of phosphorus and solidsconcerns) or the leaching of biosolids to groundwater (primarily because ofnitrate concerns) To this end for Class B and other non-EQ biosolids EPA
BIOSOLIDS MANAGEMENT 88
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age
brea
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inal
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s w
ord
brea
ks h
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s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
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grap
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TABLE 2ndash21 Minimum Duration Between Application and HarvestGrazingAccessforClass B Biosolids Applied to the LandCriteria Surface Incorporation InjectionFood crops whose harvested part maytouch the soilbiosolids mixture (beansmelons squash etc)
14 mo 14 mo 14 mo
Food crops whose harvested parts growin the soil (potatoes carrots etc)
2038 moa 38 mo 38 mo
Food feed and fiber crops (field cornhay sweet corn etc)
30 d 30 d 30 d
Grazing of animals 30 d 30 d 30 dPublic access restrictionHigh potentialb 1 y 1 y 1 yLow potential 30 d 30 d 30 d
aThe 20 month duration between application and harvesting applies when the biosolids that aresurface applied stays on the surface for 4 months or longer prior to incorporation into the soil The38 month duration is in effect when the biosolids remain on the surface for less than 4 months priorto incorporationbThis includes application to turf farms which place turf on land with a high potential for publicexposureSource Adapted from 40 CFR Part 503
requires minimum setback distances of 10 meters from surface watersalthough at least 21 states have increased their minimum setback distancebetween 50 and 300 feet Such factors as slope buffer strips method ofbiosolids application and the designated uses of nearby surface waters may beconsidered by states in setting setback distances EPA also requires thatapplication of non-EQ biosolids be limited to accommodate the nitrogenrequirements of the crop to be grown Notably federal statutes do not includegroundwater in the definition of waters of the United States and thus nominimum depth to groundwater or bedrock is included in federal regulationsHowever at least 23 states include such requirements and at least 10 haveprohibited land application of biosolids during winter months Whilerecognizing that there are vast differences in topography weather and soilconditions across the country EPA would be well advised to include morespecific site requirements in its biosolids regulations including minimum depthto groundwater controls on winter application and setback distances fromresidences
BIOSOLIDS MANAGEMENT 89
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inal
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brea
ks h
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nd o
ther
type
setti
ng-s
peci
fic fo
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how
ever
can
not b
ere
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ed a
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grap
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as th
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In addition stockpiling of biosolids in fields should only be done withfully stabilized and treated biosolids for very short durations (generally for nomore than 72 h) and in a manner that ensures there is no runoff to surface wateror adjacent land Storage at treatment plants or off-site engineered facilitiesshould be considered to avoid the need to land apply during inclement weatherconditions
Most states mimic the federal requirements for limiting land-applicationrates to accommodate the nitrogen requirements of the intended crops Nitrogenis the limiting factor in assessing application rates The application rate must bebased on the nitrogen needs of the crop to be grown Available nitrogen shouldbe assessed based on mineralization rates for the organic nitrogen and methodof application for the ammonium-nitrogen Nitrogen supplied from all othersources must also be taken into account This should be implemented throughcommunication between the land applier and the farmer Because of thesenitrogen limitations biosolids are the most regulated fertilizer or soilamendment used on agricultural land However a small but growing number ofstates are also limiting the application rate based on the phosphorus needs of thecrop or some other phosphorus index As animal waste becomes furtherregulated based on phosphorus content phosphorus consideration is likely tohave an impact on the biosolids program as well (Animal waste has not to datebeen regulated to address pathogen or nutrient control) Excess phosphorusoften becomes a water-quality problem after it reaches surface waters becauseit promotes accelerated algae growth and eutrophication For these reasonswastewater treatment plants are increasingly being forced to limit thephosphorus in their effluent discharge to surface waters Therefore thephosphorus concentration in sewage sludge is necessarily increasing Althoughthe Part 503 rule does not address phosphorus many states require setbackdistances slope restrictions and winter prohibitions to minimize the potentialfor runoff and the associated problems with phosphorus
End-Use Practices
The WDNR has worked with all states to gain information regardingbiosolids-use practices quality pathogen control and vector-attractionreduction The following data from 37 states represent the best estimation ofcurrent biosolids use in the United States (WDNR unpublished data 2001)
bull 56 million dry tons of biosolids are used or disposed ofbull Of that 34 million dry tons of biosolids are used as soil amendments
BIOSOLIDS MANAGEMENT 90
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inal
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ng-s
peci
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andor fertilizer in the United States representing 61 of the total amountused or disposed of
- 24 million dry tons of biosolids are land applied representing 43 ofthe total amount used or disposed of
- 1 million dry tons of biosolids are land applied or publicly distributed asEQ biosolids representing 18 of the total amount used or disposed of
bull 095 million dry tons of biosolids are disposed of in licensed municipalsolid waste landfills representing 17 of the total amount used ordisposed of
bull 008 million dry tons of biosolids are disposed of in surface disposal unitsrepresenting 1 of the total amount used or disposed of
bull 11 million dry tons of biosolids are burned through incinerationrepresenting 20 of the total amount used or disposed of
CHARACTERIZATION OF BIOSOLIDS
Several national surveys of biosolids quality have been conducted by EPAand the Association of Metropolitan Sewerage Agencies (AMSA) to quantifyconcentrations of pollutants and nutrients in biosolids In addition states havecollected data on biosolids as part of their biosolids program management andcompliance monitoring for many years Compliance is tracked largely throughstate programs and through the federal Biosolids Data Management System(BDMS) and Permit Compliance System (PCS) For chemicals monitoring isrequired for total percent solids the nine regulated inorganic compounds totalnitrogen and total nitrogen ammonium For pathogens the pathogen densityrequirements for Class A and Class B biosolids (discussed earlier in thischapter) are monitored Vector attraction reduction requirements are alsomonitored Minimum monitoring requirements are specified in 40 CFR 503based on the quantity of biosolids used or disposed of (see Table 2ndash22)
The current Part 503 regulations require that monitored biosolids must berepresentative of what is actually going to be used or disposed of Whenever thebiosolids are changed so that their characteristics change new sampling musttake place
The success of the pretreatment program is illustrated in the reducedconcentrations of selected inorganic pollutants in biosolids since theimplementation of regulations on nondomestic discharges to sewerage systemsThe data for biosolids show significant reductions in some of the regulatedinorganic chemicals from the inception of the pretreatment program until the
BIOSOLIDS MANAGEMENT 91
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ngth
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ord
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ther
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ng-s
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ever
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TABLE 2ndash22 Frequency of Monitoring and Land Application and Landfilling
Amount of Biosolids (drymetric tons per 365 days)
Amount of Biosolids (dryUS tons per 365 days)a
Frequency ofMonitoring
0ltXlt290 0ltXlt320 Once per y290`Xlt1500 320`Xlt1654 Once per quarter1500`Xlt15000 1654`Xlt16540 Once per 60 d15000`X 16540`X Once per mo
aAmount that is land applied or landfilled on a dry weight basisbMetric tons=US tonstimes0907Source 40 CFR 503
mid-1990s when the concentrations leveled off For example datacollected in Pennsylvania from 1978 to 1997 showed large decreases incadmium copper lead mercury nickel and zinc and smaller rates ofdecreases for arsenic selenium and molybdenum (Stehouwer et al 2000)Wisconsin and New Jersey have extensive biosolids monitoring data and willbe used for illustrative purposes Tables 2ndash23 and 2ndash24 show pollutantconcentrations over time The numbers presented are state averages TheWisconsin data include any outlier data and nondetects are considered at thedetection limit Data from Portland Oregon (Portland 2002) Seattlemetropolitan area (King County 2000) and Milwaukee metropolitan area(MMSD 2001) depict similar trends
In addition to the regulated pollutants within EPArsquos biosolids program thepretreatment program is charged with controlling the 126 ldquopriority pollutantsrdquoas well as any other incompatible pollutants from industries that discharge intothe sewer systems as described in the Clean Water Act (EPA 1999a) There arefour criteria under the pretreatment program as described earlier Those criteriaare directed towards ensuring compliance with permits Selected contaminantsin their wastewater are monitored by industries to which the pretreatmentprogram or local ordinance limits apply and also in the effluent discharge of thePOTWs covered by the pretreatment program Toxic organic chemicalsdischarged to a POTW may be volatilized degraded deposited in the sewagesludge or passed through to the effluent Monitoring of the wastewater effluentmay be required for the 126 priority pollutants but there is no federalrequirement to test sewage sludge for them nor federal limits on most of theirconcentration in biosolids One issue with monitoring for these constituents isthat on the rare occasion that one or more of them are detected there are noestablished criteria levels of concern for many of them Reliable data on theimpact of pretreatment programs on the concentration of toxic organicchemicals in biosolids are not currently available
BIOSOLIDS MANAGEMENT 92
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TA
BL
E 2
ndash23
Wis
cons
in D
ata
(all
val
ues
are
in m
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gram
s pe
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am o
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Ele
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t19
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8519
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9119
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9720
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08
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2C
d23
718
828
817
711
27
26
36
0C
r1
053
699
777
363
247
117
7389
Cu
821
792
873
702
586
573
575
540
Pb
326
310
248
182
130
9577
63H
g3
45
28
24
23
93
82
63
4M
o36
2221
20N
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113
092
8352
4143
36S
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55
58
610
9Z
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881
204
51
631
136
01
054
921
892
847
Sour
ce W
DN
R u
npub
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ed d
ata
200
1
BIOSOLIDS MANAGEMENT 93
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TABLE 2ndash24 New Jersey Data (all values are in milligram per kilogram of dryweight)Element 1981ndash1983 1989ndash1994 1997As 27 285 433Cd 94 56 35Cr 93 39 26Cu 825 679 628Pb 210 100 65Hg 36 23 19Mo 15 13Ni 46 31 23Se 20 49Zn 1110 826 810
Source New Jersey Department of Environmental Protection unpublished data 2001
PCBs were considered a group of related organic compounds in the initialdevelopment of the Part 503 regulations but ultimately were not regulatedbecause their production had already been banned in the United StatesHowever 12 coplanar PCBs are still under consideration for regulation in Part503 A 2000 survey of 50 biosolids samples in Wisconsin found detectedconcentrations of total PCBs in 40 of the samples when the analysis wasperformed on an aroclor basis (WDNR unpublished material 2000) A furtheranalysis of a subset of the 50 samples (samples with detectable aroclors sixwith nondetectable aroclor samples and one resample) on a congener-specificbasis found detectable concentrations in 100 of the samples A similar 2001EPA survey of 101 biosolids samples from across the nation also founddetectable concentrations of coplanar PCBs (EPA 2002a) The total PCBconcentration mean in the Wisconsin survey was 023 mgkg for the arocloranalyses and 03 mgkg for the congener-specific analyses Current regulationsin 40 CFR 761 state that land-applied biosolids with concentrations of totalPCBs at less than 50 mgkg are regulated under 40 CFR 503 and sewage sludgewith concentrations greater than 50 mgkg cannot be land applied and is subjectto provisions within that regulation (EPA 1998) Furthermore 40 CFR 257requires industrial sludge with concentrations of total PCBs at greater than 10mgkg to be injected or incorporated when land applied
EPArsquos stated purpose in their sampling survey of 2001 was to determinetoxicity equivalent concentrations (TEQs) for the 29 congeners of dioxins
BIOSOLIDS MANAGEMENT 94
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furans and coplanar PCBs which they proposed to add to 40 CFR 503 Themean TEQ value for total dioxin and dioxin-like compounds was 3160nanograms per kilogram (ngkg) DM when nondetect measurements weresummed at one-half the detection limit (EPA 2002a) AMSA also conducted asurvey of member and nonmember facilities in late 2000 (Alvarado et al 2001)A total of 197 biosolids samples were collected from 170 facilities and meanand median TEQ concentrations of 485 and 217 ngkg were reportedrespectively The TEQ values ranged from 71 to 256 ngkg with a single outlierof 3590 ngkg Notably these TEQ concentrations are lower than thosereported in a similar survey conducted in 1994 (Green et al 1995) This findingmay be due to fewer medical-waste incinerators in operation and other reducedcombustion sources of dioxin but may in large part be explained by improvedanalytical techniques In all three surveys nondetectable congeners weresummed at one-half the detection concentration As detection concentrationscontinue to decrease so too do the added values of nondetections
The State of Vermont recently reported the results of a survey of the 17dioxin and furan congeners (but excluded coplanar PCBs) in a sampling of 20POTWs and 3 comingling EQ generating facilities (Kelley 2000) A total of 28samples were collected in November and December 1996 and in August 1998The mean and median TEQ concentrations were 1122 and 855 pptrespectively and the range was from 132 to 5944 ppt One importantdifference in the Vermont survey data compared with the EPA and AMSA datais that nondetectable congeners were summed as zero rather than one-half thedetection limit
COMPLIANCE ASSISTANCE AND ENFORCEMENT
Perhaps the most common and vocal complaint of EPArsquos biosolidsprogram is the lack of federal presence to ensure compliance with the existingregulations In the absence of that assurance and as the report of the Office ofthe Inspector General (OIG) concluded (EPA 2000b) EPA cannot claim thatthe regulations are followed and that public health and the environment areprotected as required by the CWA States do however implement their ownbiosolids programs to some greater or lesser extent and actively participate inboth compliance assistance and enforcement
State regulators report substantial compliance is prevalent when assessedEPArsquos Office of Enforcement and Compliance Assistance has taken a formalposition that biosolids are a low public-health and environmental priority andthus no formal program policy is in place However according to EPA all 10regional offices will take appropriate action as required if a case is brought totheir attention (DRegas EPA personal communication to OIG June 11
BIOSOLIDS MANAGEMENT 95
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2001) Although some EPA regional offices are more aggressive and involvedthan others little enforcement action is taken at the federal level Furthermoreenforcement strategies differ between states and EPA states tend to favorstepped enforcement that focuses on compliance assistance and education andEPA is likely to levy monetary penalties with less discussion
EPA recently established an incident-response team as part of theBiosolids Program Implementation Team to address and investigate criticalallegations of sewage sludge and biosolids violations and public-health threatsA problem this team has faced is that they are not notified of situations in atimely manner There is currently no process for registration or follow-up oncomplaints and alleged violations An administrative framework is necessary totrack such allegations investigations and outcomes
FINDINGS AND RECOMMENDATIONS
EPA provides insufficient support and oversight to the biosolids programEPA gives low priority to its biosolids program because it contends that risksfrom exposure to chemicals and pathogens in biosolids are low and that land-application programs generally function as intended and in compliance with theregulations This contention should be better substantiated
Recommendations
bull EPA should strengthen its biosolids-oversight program by increasing theamount of funding and staff (technical and administrative) devoted to it
bull EPA should provide additional funds (not diverted funds) to states toimplement biosolids programs and facilitate delegation of authority tostates to administer the federal biosolids regulations
bull Resources are also needed for conducting research into emerging issuesand to revise the regulations as appropriate and in a timely fashion (egmolybdenum standards should be proposed)
bull A process should be established to track allegations and sentinel events(compliance management or health based) investigations andconclusions Such tracking should be systematic developed incooperation with states and should document both positive and negativeoutcomes
The Pathogen Equivalency Committee (PEC) performs invaluabletechnical support and process assessment
Recommendations
bull The PEC should be funded supported and officially sanctioned as anintegral part of the federal biosolids program The following areimportant in supporting the PEC
BIOSOLIDS MANAGEMENT 96
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mdash The PEC members should have a formal portion of their time allocatedto PEC responsibilities
mdash Travel funds should be put at the disposal of the PEC to enable meeting attendance and visits to selected sites of petitioners
mdash There is a perception on the part of PEC members that EPArsquosCincinnati laboratories do not include biosolids as a formal part of theirmission statement This needs to be clarified and rectified
mdash formal procedure for designation of backup members should be devised
Biosolids risk-management practices are an integral component of the riskassessment and technological criteria that were used to establish the standardsof the Part 503 rule They are therefore an important component of theregulations for chemicals and pathogens
Recommendations
bull Studies should be conducted to determine whether the managementpractices specified in the Part 503 rule (eg 10-meter setback fromwaters) achieve their intended effect
bull Additional risk-management practices should be considered in futurerevisions to the Part 503 rule including setbacks from residences orbusinesses setbacks from private and public water-supply wells sloperestrictions soil permeability and depth to groundwater or bedrock andreexamination of whether a greater setback distance to surface water is warranted
bull Provisions for allowing distribution of Class A biosolids in bags or othercontainers (weighing less than 1 metric ton) should not be allowed whenthey do not meet pollutant concentration limits (ie all biosolids sold orgiven away should be EQ)
bull Exemptions from nutrient management and site restrictions for landapplication of bulk EQ biosolids should be eliminated
There are several prescribed treatment processes that can be used to meetregulatory requirements for classifying biosolids as Class A or Class BHowever the efficacy of the treatment processes needs verification and thestabilization regulations need to be refined for consistent control of vectorattraction
Recommendations
bull EPA should conduct national field and laboratory surveys to verify thatClass A and Class B treatment processes perform as assumed by theirengineering and design principles Determinations should be made ofpathogen density and elimination across the various accepted treatmentprocesses and in the biosolids or environmental media over time
bull Standard treatment design criteria should be adopted nationally to ensurecompliance with existing biosolids regulations
BIOSOLIDS MANAGEMENT 97
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bull Stabilization controls need to be further refined and directly correlated tometabolic techniques (eg SOUR test carbon dioxide metabolic releasemethane metabolic release)
The available methods for detecting and quantifying pathogens in biosolidshave not been validated There have been a number of advances in detectionand quantification of pathogens in the environment and in approaches toenvironmental sample collection and processing However no consensusstandards have been developed for pathogen measurements in biosolids
RecommendationEPA should support development standardization and validation of
detection and quantification methods for pathogens and indicator organismsregulated under the Part 503 rule The sufficiency of these methods and theirresults should be considered in conducting and interpreting future riskassessments and used to develop applicable risk-management technologies
The CWA requires EPA to establish biosolids regulations based on riskhowever it is important to acknowledge and consider other approaches toregulating land application of biosolids
RecommendationAs part of the process of revising the Part 503 rule EPA should review
biosolids protocols used by other nations This could provide valuable newperspectives and insights into the scientific technical and societal bases for thedevelopment and implementation of biosolids regulations
EPA and the US Department of Agriculture cosponsored a workshop onemerging pathogens in June 2001 with international experts in the field Thecommittee supports the major research recommendations from that workshop(listed below)
RecommendationsResearch is needed on the following topics
bull Pathogen survival in processing or emissions during the treatment processbull Vectors carrying pathogens and toxinsbull Bioaerosols and other chemical aerosolsbull Test-method development and validation for various organisms in sewage
sludge and biosolidsbull Field verification of efficacy of Class A and Class B treatment processes
(including data to directly relate process controls to initial and finalpathogen and indicator densities)
BIOSOLIDS MANAGEMENT 98
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bull Development of indicator pathogens for assessment of impact andattenuation in field situations
REFERENCES
Alvarado MJ SArmstrong and ECrouch 2001 The AMSA 20002001 Survey of Dioxin-likeCompounds in Biosolids Statistical Analyses Prepared by Cam bridge EnvironmentalInc Cambridge MA for the Association of Metropolitan Sewerage Agencies (AMSA)October 30 2001 [Online] Available httpwwwamsa-cleanwaterorgadvocacydioxinfinal_reportpdf [May 17 2002]
Burnham JC NHatfield GFBennett and TJLogan 1992 Use of kiln dust with quicklime foreffective municipal sludge pasteurization and stabilization with the N-Viro soil processPp 128ndash141 in Innovations and Uses for Lime DDWalker Jr TBHardy DCHoffmanand DDStanley eds ASTM STP 1135 Phildelphia PA American Society for Testingand Materials
Burton NC and DTrout 1999 NIOSH Health Hazard Evaluation Report BioSolids LandApplication Process LeSourdsville Ohio HETA 98ndash0118ndash2748 US Department ofHealth and Human Services Public Health Service Centers for Disease Control andPrevention National Institute for Occupational Safety and Health
Cooperative State Research Service Technical Committee W-l70 1989 Peer Review Standards forthe Disposal of Sewage Sludge US EPA Proposed Rule 40 CFR Parts-257 and 503(February 6 1989 Federal Register pp 5746ndash5902) Submitted to William RDiamondCriteria and Standards Division US Environmental Protection Agency WashingtonDC US Dept of Agriculture Cooperative State Research Service
Council of the European Communities 1986 Council Directive 86278EEC of 12 June 1986 on theProtection of the Environment and in Particular of the Soil When Sewage Sludge is Usedin Agriculture Community Legislation in Force Document 386L0278 [Online]Available httpeuropaeuinteur-lexenlifdat1986en_386L0278html [September 122001]
EPA (US Environmental Protection Agency) 1979 Criteria for classification of solid wastedisposal facilities and practices Fed Regist 44(179)53460ndash53464 (September 13 1979)
EPA (US Environmental Protection Agency) 1981 Land Application of Municipal SewageSludge for the Production of Fruits and Vegetables A Statement of Federal Policy andGuidance SW 905 US US Environmental Protection Agency US Food and DrugAdministration and US Department of Agriculture Washington DC
EPA (US Environmental Protection Agency) 1984 Municipal sludge management policy NoticeFed Regist 49(114)24849ndash24850 (June 12 1984)
EPA (US Environmental Protection Agency) 1985 Pathogen Risk Assessment Feasibility StudyEPA 6006ndash88003 Office of Research and Development
BIOSOLIDS MANAGEMENT 99
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age
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lin
e le
ngth
s w
ord
brea
ks h
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tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
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tain
ed a
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grap
hic
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ibut
ion
Office of Health and Environmental Assessment Environmental Criteria and AssessmentOffice US Environmental Protection Agency Cincinnati OH November 1985
EPA (US Environmental Protection Agency) 1989 Environmental Regulation and TechnologyControl of the Pathogens in Municipal Wastewater Sludge for Land Application UnderCFR Part 257 Office of Technology Transfer and Regulatory Support USEnvironmental Protection Agency Cincinnati OH September 1989
EPA (US Environmental Protection Agency) 1990 National sewage sludge survey Availabilityof information and data and anticipated impacts on proposed regulations Fed Regist 55(218)47210ndash47283 (November 9 1990)
EPA (US Environmental Protection Agency) 1991 Interagency policy on beneficial use ofmunicipal sewage sludge on federal land Notice Fed Regist 56(138)33186ndash33188 (July18 1991)
EPA (US Environmental Protection Agency) 1992 Technical Support Document for Reduction ofPathogens and Vector Attraction in Sewage Sludge EPA 822R-93ndash004 Office of WaterUS Environmental Protection Agency November 1992
EPA (US Environmental Protection Agency) 1993 Federal Register February 19 1993 40 CFRParts 257 403 and 503 The Standards for the Use or Disposal of Sewage Sludge FinalRules EPA 822Z-93001 US Environmental Protection Agency
EPA (US Environmental Protection Agency) 1994 Federal register amendment to 40 CFR503Fed Regist 59(38)9095ndash9100 (February 25 1994)
EPA (US Environmental Protection Agency) 1995a A Guide to the Biosolids Risk Assessmentsfor the EPA Part 503 Rule EPA 832-B-93ndash005Office of Wastewater Management USEnvironmental Protection Agency Washington DC September 1995 [Online] Availablehttpwwwepagovowmbio503ruleindexhtm [December 20 2001]
EPA (US Environmental Protection Agency) 1995b Sewage sludge Use or disposal standardsFed Regist 60(206)54771ndash54792 (October 25 1995)
EPA (US Environmental Protection Agency) 1998 Part IV 40 CFR Parts 750 and 761 Disposalof polychlorinated biphenyls (PCBs) Final Rule Fed Regist 63(124)35383ndash35474(June 29 1998)
EPA (US Environmental Protection Agency) 1999a Introduction to the National PretreatmentProgram EPA-833-B-98ndash002 Office of Wastewater Management US EnvironmentalProtection Agency February 1999 [Online] Available wwwepagovnpdespubsfinal99pdf [March 19 2002]
EPA (US Environmental Protection Agency) 1999b Environmental Regulations and TechnologyControl of Pathogens and Vector Attraction in Sewage Sludge EPA625R-92013 Officeof Research and Development US Environmental Protection Agency Washington DC[Online] Available httpwwwepagovttbnrmrl625R-92013htm [January 4 2002]
BIOSOLIDS MANAGEMENT 100
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
EPA (US Environmental Protection Agency) 1999c Standards for the use or disposal of sewagesludge Proposed rule Fed Regist 64(246)72045ndash72062 (December 23 1999)
EPA (US Environmental Protection Agency) 2000a Progress in Water Quality An Evaluation ofthe National Investment in Municipal Wastewater Treatment EPA-832-R-00ndash008 Officeof Wastewater Management Office of Water US Environmental Protection AgencyJune 2000 [Online] Available httpwwwepagovOWOWMhtmlwqualitybenefitshtm[May 16 2002]
EPA (US Environmental Protection Agency) 2000b Water Biosolids Management andEnforcement Audit Report No 2000-P-10 Office of Inspector General March 20 2000[Online] Available httpwwwepagovoigearthauditlist30000P0010pdf [December20 2001]
EPA (US Environmental Protection Agency) 2000c OECArsquos Response to IG Report on Biosolids(2000-P-10) Memorandum from Steven AHerman Assistant Administrator Office ofEnforcement and Compliance Assurance to Jonathan CFox Assistant AdministratorOffice of Water US Environmental Protection Agency Washington DC June 23 2000
EPA (US Environmental Protection Agency) 2001a Final Audit Report on Biosolids Managementand Enforcement (No 2000-P-10) Memorandum to Michael Simmons Deputy AssistantInspector General for Internal Audits from Diane CRegas Acting AssistantAdministrator Office of Water US Environmental Protection Agency Washington DCJune 11 2001
EPA (US Environmental Protection Agency) 2001b Agency Response to Biosolids Managementand Enforcement Audit Report No 2000-P-10 Memorandum to GTracy Mehan AssistantAdministrator for Water and Sylvia KLowrance Acting Assistant Administrator forEnforcement and Compliance Assurance from Judith JVanderhoef Project ManagerHeadquarters Audit Division October 5 2001
EPA (US Environmental Protection Agency) 2001c Workshop on Emerging Infectious DiseaseAgents and Associated With Animal Manures Biosolids and Other Similar By-ProductsCincinnati OH June 4ndash6 2001 National Risk Management Research Laboratory USEnvironmental Protection Agency Cincinnati OH
EPA (US Environmental Protection Agency) 2002a Standards for the Use or Disposal of SewageSludge Notice Fed Regist 67(113)40554ndash40576 (June 12 2002)
EPA (US Environmental Protection Agency) 2002b Biosolids Management and EnforcementOIG Audit Report No 2000-P-10 Memorandum to Judith J Vanderhoef ProjectManager Headquarters Audit Division and Michael Wall Acting Divisional Inspector forAudit Headquarters Audit Division from GTracy Mehan Assistant Administrator forWater and Sylvia KLowrance Acting Assistant Administrator for Enforcement andCompliance Assurance US Environmental Protection Agency Washington DC Jan30 2002
EPA (US Environmental Protection Agency) 2002c Land Application of Biosolids Status Report2002-S-000004 Office of Inspector General US Environmental Agency March 28 2002
BIOSOLIDS MANAGEMENT 101
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
European Communities 2001 Disposal and Recycle Routes for Sewage Sludge Part 1 Sludge UseAcceptance Part 2 Regulatory Report European Communities DG EnvironmentLuxembourg Office for Official Publications of the European Communities October2001 [Online] Available httpeuropaeuintcommenvironmentsludgesludge_disposalhtm [March 27 2001]
European Union 2000a Waste management Chapter 4 in Handbook for Implementation of EUEnvironmental Legislation Enlargement and Co-Operation with European ThirdCountries Europa The European Union On-Line [Online] Available httpeuropaeuintcommenvironmentenlarghandbookwastepdf [September 12 2001]
European Union 2000b Working Document on Sludge 3rd Draft ENVE3LM European UnionBrussels April 27 2000 The European Union On-Line Available httpeuropaeuintcommenvironmentsludgesludge_enpdf [March 20 2002]
Gendebien A CCarlton-Smith MIzzo and JEHall 1999 UK Sewage Sludge Survey-NationalPresentation RampD Technical Report P 165 Environmental Agency Bristol UK
GLUMB (Great Lakes-Upper Mississippi River Board of State and Provincial Public Health andEnvironmental Managers) 1997 Recommended Standards for Wastewater FacilitiesAlbany NY Health Education Service
Green LC EACCrouch SRArmstrong TLLash and RLLester 1995 Comments onEstimating Exposure to Dioxin-Like Compounds Review Draft CambridgeEnvironmental Inc Cambridge MA January 12 1995
Haas CN 2001 Assessment of the PEC Process Report to US EPA Pathogen EquivalencyCommittee (PEC) Philadelphia PA Drexel University Philadelphia PA January 2 2001
Harrison EZ and MMEaton 2001 The role of municipalities in regulating the land applicationof sewage sludges and spetage Nat Res J 41(1)77ndash123
Keeney DR KWLee and LMWalsh 1975 Guidelines for the Application of WastewaterSludge to Agricultural Land in Wisconsin Technical Bulletin 88 Madison WIDepartment of Natural Resources
Kelley EF 2000 Vermont Biosolids Dioxin Sampling Project Final Report Vermont Departmentof Environmental Conservation December 7 2000
Kester G 2000a Letter to Chairman FJames Sensenbrenner US House of RepresentativeCommittee on Science Washington DC from GKester State Residuals CoordinatorBureau of Watershed Management State of Wisconsin Department of Natural ResourcesMadison WI April 6 2000
Kester G 2000b Letter to Michael Cook Director Office of Wastewater Management USEnvironmental Protection Agency Washington DC from GKester Wisconsin ResidualsCoordinator Bureau of Watershed Management State of Wisconsin Department ofNatural Resources Madison WI February 23 2000
Kester G 2000c Letter to Mike Cook Director Office of Wastewater Management USEnvironmental Protection Agency Washington DC from G Kester Wisconsin ResidualsCoordinator Bureau of Watershed Management State of Wisconsin Department ofNatural Resources Madison WI October 2 2000
BIOSOLIDS MANAGEMENT 102
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Kester G 2001a Letter to Michael BCook Director Office of Wastewater Management ElaineGStanley Director Office of Compliance Brian JMaas Director Water EnforcementDivision Eric VSchaffer Director Office of Regulatory Enforcement Elliott JGilbergDirector Chemical Commercial Services and Municipal Division and Frederick FStiehlDirector Environmental Planning Targeting and Data Division US EnvironmentalProtection Agency Washington DC from GKester State Residuals Coordinator Bureauof Watershed Management State of Wisconsin Department of Natural ResourcesMadison WI January 9 2001
Kester G 2001b Letter to The Honorable Christine Todd Whitman Administrator USEnvironmental Protection Agency Washington DC from GKester State ResidualsCoordinator Bureau of Watershed Management State of Wisconsin Department ofNatural Resources Madison WI September 10 2001
King County 2000 Biosolids Quality Summary Biosolids Management Program King CountyDepartment of Natural Resources Wastewater Treatment Division Seattle WA July 2001
Kowal NE 1985 Health Effects of Land Application of Municipal Sludge EPA6001ndash85015Health Effects Research Laboratory Office of Research and Development USEnvironmental Protection Agency Research Triangle Park NC (cited in EPA 1992)
Lodor ML 2001 NIOSH reports omits significant details in LeSourdsville case BiosolidsTechnical Bulletin 7(4)11ndash13
Matthews P ed 1996 Global Atlas of Wastewater Sludge and Biosolids Use and DisposalScientific and Technical Report No 4 London International Association on WaterQuality 197 pp
McGrath SP ACChang ALPage and EWitter 1994 Land application of sewage sludgeScientific perspectives of heavy metal loading limits in Europe and the United StatesEnviron Rev 2108ndash118
Meyer GE 1998 Letter to JCharles Fox Assistant Administrator Office of Water USEnvironmental Protection Agency Washington DC from GEMeyer Secretary State ofWisconsin Department of Natural Resources Madison WI November 13 1998
MMSD (Milwaukee Metropolitan Sewerage District) 2001 Pretreatment Program EffectivenessAnalysis 2000 Milwaukee Metropolitan Sewerage District May 2001
NIOSH (National Institute for Occupational Safety and Health) 2000 Workers Exposed to Class BBiosolids During and After Field Application NIOSH Hazard ID HID 10 DHHS(NIOSH) 2000ndash158 National Institute for Occupational Safety and Health Centers forDisease Control and Prevention Public Health Service US Department of Health andHuman Services August 2000
NIOSH (National Institute for Occupational Safety and Health) 2002 Guidance for ControllingPotential Risks to Workers Exposed to Class B Biosolids DHHS (NIOSH) 2002ndash149National Institute for Occupational Safety and Health Centers for Disease Control andPrevention Public Health Service US Department of Health and Human ServicesPreprint June 12 2002
BIOSOLIDS MANAGEMENT 103
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
NRC (National Research Council) 1996 Use of Reclaimed Water and Sludge in Food CropProduction Washington DC National Academy Press
OrsquoConnor G RBBrobst RLChaney RLKincaid LRMcDowell GM Pierzynski ARubinand GGVan Riper 2001 A modified risk assessment to establish molybdenum standardsfor land application of biosolids J Environ Qual 30(5)1490ndash1507
Pedersen D 1981 Density Levels of Pathogenic Organisms in Municipal Wastewater Sludge ALiterature Review EPA-6002ndash81ndash170 NTIS PB82ndash102286 Boston MA Camp Dresseramp McKee Inc
Peavy HS DRRowe and GTchobanoglous 1985 P 278 in Environmental Engineering NewYork McGraw-Hill
Portland 2002 Biosolids Management Plan Bureau of Environmental Services City of PortlandFebruary 2002
Razvi A 2000 Audit Report of DNR Septage Management Program College of NaturalResources University of Wisconsin-Stevens Point August 15 2000
Reimers RS ACAnderson AAAbdelhgani MCLockwood and LEWhite 1986a The usageof non-ionizing irradiation processes in the disinfection of water and wastes Pp 272ndash299in Applied Fields for Energy Conservation Water Treatment and Industrial ApplicationsFinal Report RSReimers SFBock and LEWhite eds DOECE40568-T1(DE86014306) Washington DC Technical Information Center Office of Scientific andTechnical Information US Department of Energy June 1986
Reimers RS MDLittle AJEnglande DBMcDonell DDBowman and JM Hughes 1986bInvestigation of Parasites in Sludges and Disinfection Tech niques EPA 6001ndash85022NTIS PB 86ndash135407 Prepared by the School of Public Health and Tropical MedicineTulane University New Orleans LA for the Health Effects Research LaboratoryResearch Triangle Park NC
Reimers RS AJEnglande RMBakeer DDBowman TACalamari HBBrad fordCFDufrechou and MMAtique 1999 Update on Current and Future Aspects ofResource Management for Animal Wastes WEFTEC rsquo99 Pre-Con ference WorkshopldquoBeneficial Use of Animal Waste Residuals-A Mandatory Aim for the 21st CenturyrdquoWater Environment Federation Alexandria VA October 1999
Reimers RS DDBowman PLSchafer PTata BDLeftwich and MMAtique 2001 FactorsAffecting Lagoon Storage Disinfection of Biosolids Proceedings of Joint WEFAWWACWEA Specialty Conference ldquoBiosolids 2001rdquo CD-ROM Water EnvironmentalFederation Alexandria VA February 2001
Stehouwer RC AMWolf and WTDoty 2000 Chemical monitoring of sewage sludge inPennsylvania Variability and application uncertainty J Environ Qual 29(5)1686ndash1695
UK Department of the Environment 1993 Sludge Use in Agriculture 19901991 Report to the ECCommission Under Directive 86278EEC Department of the Environment HMSOLondon
Wisconsin Administrative Code 1996 Domestic Sewage Sludge Management Chapter NR 204Register 49115ndash37 Department of Natural Resources State
BIOSOLIDS MANAGEMENT 104
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
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of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
of Wisconsin Department of Administration [Online] Available httpwwwdoastatewiusdsasdocservdocsaleswiscodeasp [March 27 2002]
BIOSOLIDS MANAGEMENT 105
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t th
is P
DF
file
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s ne
w d
igita
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rese
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of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
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ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
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iden
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inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
3
Epidemiological Evidence of Health EffectsAssociated with Biosolids Production and
Application
This chapter reviews the epidemiological literature concerning workersand community residents potentially exposed to biosolids during production andapplication This literature is valuable for four reasons (1) it may providedocumentation of human-health consequences of exposure to biosolids underthe circumstances of their production application and use (2) it may provideinformation on routes of exposure such as airborne transmission or ingestion(3) it may provide information on a dose-response relationship and (4) it mayidentify gaps in the literature Recognition of gaps is essential to distinguishbetween no evidence of effect and evidence of no effect Finally even thoughall prediction is based on logical extension from available information anepidemiological review can provide an assessment of the strength of theknowledge foundation from which predictions are made
The committee was apprised of various human-health allegationsassociated with biosolids exposure from news articles written submissions fromthe public and citizens who attended its public meetings It was beyond thecommitteersquos charge to investigate or verify these allegations Thus thecommittee limited review to studies published in the peer-reviewed literatureand reports from government agencies The review included studies thatinvestigated health effects or provided biomonitoring data (evidence ofbiological absorption [ie chemical absorption into the body]) and excludedstudies limited to human exposure without evidence of biological absorption orhuman health effects Although the committee was asked to focus on publichealth the review includes epidemiological studies involving production andapplication
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
106
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t th
is P
DF
file
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s ne
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igita
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rese
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of t
he o
rigin
al w
ork
has
been
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ompo
sed
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L fil
es c
reat
ed f
rom
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inal
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er b
ook
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tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
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ord
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ks h
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tyle
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ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
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ome
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grap
hic
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ay h
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rted
Ple
ase
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prin
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sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
of biosolids by workers in addition to assessments of health effects incommunity residents The rationale for inclusion of information on workerexposure is that occupational exposure which for many toxicants is usuallyhigher in exposed workers than in residents exposed from the generalenvironment often provides a substantial basis for extrapolating risk assessmentfrom higher occupational concentrations to lower environmental concentrations
The committee also considered potential risks from odors and diseasevectors but did not find any epidemiological studies of these types of risksrelated to biosolids Odors and disease vectors have often been categorized asnuisance or aesthetic issues but odors can have adverse physiological andpsychological effects (see Chapter 5) and vectors can transmit disease (seeChapter 6) These are issues that need careful consideration as there appears tobe a fine line between when odors or disease vectors are merely nuisance issuesand when they are health issues
DESCRIPTION OF THE LITERATURE
The committee evaluated 23 studies relevant to the assessment of humanhealth effects associated with biosolids exposure and divided them into sixmajor focus populations (1) biosolids users (eg farmers and home gardeners)(2) populations near agricultural application sites (3) workers involved inbiosolids production and application (4) populations near sewage treatmentplants (5) workers in sewage treatment plants and (6) compost workers Fewepidemiological studies were conducted specifically for biosolids exposureThere are substantially more studies of workers in sewage treatment plants andpopulations living near them Although those studies do not involve exposure tobiosolids per se they were included because they provide valuable informationabout hazards to sewer workers and others exposed to raw sewage that could beused to identify potential hazards from biosolids However an exhaustivereview of the literature on exposures from sewage treatment plants was notconducted
Table 3ndash1 provides the details of the studies that the committee evaluatedA summary of the populations studied the observed outcomes and thecommitteersquos assessment is provided below
Exposed Populations
bull Biosolids users One study documents chemical exposure fromavocational gardening use of biosolids (Baker et al 1980) This singleinvesti
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
107
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t th
is P
DF
file
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s ne
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igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
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L fil
es c
reat
ed f
rom
the
orig
inal
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er b
ook
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fro
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heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TA
BL
E 3
ndash1 S
umm
ary
of H
uman
Hea
lth
Stu
dies
on
Bio
soli
ds a
nd B
ioso
lids
-rel
ated
Exp
osur
es
Stu
dy T
ype
End
Poi
nts
Eva
luat
edF
indi
ngs
Ref
eren
ces
Bio
soli
ds U
sers
Cro
ss-s
ecti
onal
Eva
luat
ion
of P
CB
exp
osur
e an
d he
alth
eff
ects
in (
1)bi
osol
ids
user
s (n
=89
) in
Blo
omin
gton
Ind
iana
ex
pose
d to
bio
soli
ds d
irec
tly
from
app
lica
tion
toga
rden
s or
indi
rect
ly f
rom
foo
ds g
row
n in
bio
soli
ds-
amen
ded
soil
s (
2) w
orke
rs o
ccup
atio
nall
y ex
pose
d to
PC
Bs
(n=
18 o
nly
1 ex
pose
d vi
a bi
osol
ids)
(3
) fa
mil
ym
embe
rs o
f w
orke
rs o
ccup
atio
nal
expo
sed
tobi
osol
ids
(n=
19)
and
(4)
indi
vidu
als
wit
h no
kno
wn
expo
sure
to P
CB
s (n
=22
) (
PC
Bs
wer
e di
scha
rged
into
the
mun
icip
al s
ewag
e sy
stem
by
a el
ectr
ical
capa
cito
r m
anuf
actu
ring
pla
nt)
Mea
n se
rum
con
cent
rati
ons
of P
CB
s w
ere
174
ppb
inbi
osol
ids
user
s 7
51
ppb
in P
CB
-exp
osed
wor
kers
33
6 p
pb in
wor
ker
fam
ily
mem
bers
an
d 24
4 p
pb in
none
xpos
ed in
divi
dual
s F
or b
ioso
lids
use
rs P
CB
seru
m c
once
ntra
tion
s w
ere
asso
ciat
ed p
osit
ivel
y w
ith
the
perc
enta
ge o
f ga
rden
car
e (p
=0
035)
and
nega
tive
ly w
ith
wea
ring
glo
ves
whi
le g
arde
ning
(p=
002
1) b
ut w
ere
not s
igni
fica
ntly
ass
ocia
ted
wit
hth
e am
ount
of
bios
olid
s us
ed o
r th
e du
rati
on o
fex
posu
re N
o ov
ert s
ympt
oms
of P
CB
toxi
city
wer
eob
serv
ed a
nd n
o co
rrel
atio
ns w
ere
foun
d be
twee
nP
CB
exp
osur
e an
d te
sts
of h
emat
olog
ical
hep
atic
or
rena
l fun
ctio
n P
lasm
a tr
igly
ceri
de c
once
ntra
tion
sw
ere
foun
d to
incr
ease
wit
h se
rum
PC
Bco
ncen
trat
ions
sug
gest
ing
that
PC
Bs
mig
ht a
lter
lipi
dm
etab
olis
m
Bak
er e
t al
1980
Pop
ulat
ions
Nea
r A
gric
ultu
ral A
ppli
cati
on S
ites
Pro
spec
tive
Thr
ee-y
ear
heal
th s
urve
y of
farm
resi
dent
s (n
=16
4)an
d do
mes
tic
anim
als
at f
arm
app
lica
tion
sit
es in
Ohi
o R
esid
ents
als
o un
der
No
sign
ific
ant d
iffe
renc
es in
the
follo
win
g pa
ram
eter
sw
ere
foun
d be
twee
n re
side
nts
at la
nd-a
ppli
cati
on s
ites
and
cont
rol s
ites
res
pira
tory
illn
ess
gas
troi
ntes
tina
lil
lnes
s o
r ge
nera
l sym
ptom
s d
isea
se
Dor
n et
al
1985
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
108
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
wen
t tub
ercu
lin
and
sero
logi
cal
test
ing
Res
ults
wer
e co
mpa
red
wit
h re
side
nts
of f
arm
s th
at d
o no
tap
ply
bios
olid
s (n
=13
0)
occu
rren
ce in
dom
esti
c an
imal
s a
nd s
erol
ogic
alco
nver
sion
s to
23
viru
ses
and
the
freq
uenc
y of
asso
ciat
ed il
lnes
ses
No
conv
ersi
ons
from
pos
itive
to n
egat
ive
tine
test
res
ults
wer
e fo
und
afte
rse
wag
e sl
udge
app
lica
tion
W
orke
rs in
Bio
soli
ds P
rodu
ctio
n an
dor
App
lica
tion
Ind
ustr
yC
ross
-sec
tion
alIn
terv
iew
s w
ith
empl
oyee
s (n
=5)
load
ing
unlo
adin
g a
nd a
pply
ing
Cla
ss B
bio
soli
ds a
nden
viro
nmen
tal
mon
itor
ing
incl
udin
g br
eath
ing-
zone
air
sam
ples
for
bac
teri
a e
ndot
oxin
s V
OC
san
d tr
ace
met
als
His
tory
of
gast
roin
test
inal
illn
ess
amon
g w
orke
rs
Ent
eric
bac
teri
a w
ere
dete
cted
in th
e ai
r an
d bu
lksa
mpl
es E
ndot
oxin
leve
ls a
t or
belo
w le
vels
fou
ndin
was
tew
ater
trea
tmen
t fac
ilit
ies
Var
ious
met
als
and
VO
Cs
wer
e lo
w A
fter
this
stu
dy w
as is
sued
it
was
rep
orte
d th
at th
e bi
osol
ids
to w
hich
the
wor
kers
wer
e ex
pose
d di
d no
t mee
t Cla
ss B
requ
irem
ents
Bur
ton
and
Tro
ut 1
999
Lod
or 2
001
Pop
ulat
ions
Nea
r S
ewag
e T
reat
men
t Pla
nts
Ret
rosp
ecti
veA
cute
illn
esse
s an
d sy
mpt
oms
repo
rted
bet
wee
n19
65 a
nd 1
971
by c
omm
unit
y in
Tec
umse
h M
I(n
=4
889)
Com
mun
ity
was
div
ided
into
conc
entr
ic r
ings
rad
iati
ng o
ut in
mul
tipl
es o
f 60
0m
fro
m a
n ac
tiva
ted
sew
age
slud
ge tr
eatm
ent p
lant
Gre
ater
than
exp
ecte
d oc
curr
ence
of
resp
irat
ory
and
gast
roin
test
inal
illn
esse
s in
com
mun
ity
livi
ngw
ithi
n 60
0 m
of
the
plan
t L
imit
atio
ns in
inte
rpre
ting
the
resu
lts
wer
e id
enti
fied
by
the
inve
stig
ator
s as
con
foun
ding
by
a de
mog
raph
ical
lyhe
tero
gene
ous
popu
lati
on (
low
soc
ioec
onom
icpo
pula
tion
) la
ck o
f ex
posu
re a
nd m
eteo
rolo
gica
lda
ta a
nd r
elat
ivel
y lo
w v
olum
e of
the
expo
sure
sour
ce
Fan
nin
et a
l 19
80
Jaku
bow
ski
1986
Ret
rosp
ecti
veM
onit
orin
g of
mic
roor
gani
sms
in th
e ai
r up
win
dan
d do
wnw
ind
ofA
bsen
teei
sm a
t the
sch
ool d
ecre
ased
dur
ing
the
2 y
afte
r th
e pl
ant b
egan
ope
rati
ons
com
pare
d w
ith
Cam
ann
et a
l 19
80
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
109
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Stu
dy T
ype
End
Poi
nts
Eva
luat
edF
indi
ngs
Ref
eren
ces
a pl
ant i
n T
igar
d O
R a
nd c
ompa
riso
n of
abse
ntee
ism
rat
es in
a n
earb
y sc
hool
bef
ore
and
afte
rth
e pl
ant o
pene
d
atte
ndan
ce d
ata
coll
ecte
d ov
er 7
y b
efor
e th
e pl
ant
open
ed
Jaku
bow
ski
1986
Pro
spec
tive
Hea
lth
surv
ey o
f co
mm
unit
y (n
=4
300)
inS
chau
mbu
rg I
L b
etw
een
1974
and
197
6 w
hich
cove
red
a pe
riod
bef
ore
and
afte
r an
act
ivat
ed s
ewag
esl
udge
trea
tmen
t pla
nt w
as o
pera
tion
al S
erol
ogic
alte
sts
and
isol
atio
n of
pat
hoge
ns f
rom
cli
nica
lsp
ecim
ens
wer
e al
so p
erfo
rmed
on
a su
bset
of
the
com
mun
ity
(n=
226)
Sig
nifi
cant
(plt
001
) in
crea
ses
wer
e fo
und
in th
ere
port
ed in
cide
nce
of s
kin
dise
ase
che
st p
ain
dia
rrhe
aw
eakn
ess
nau
sea
and
vom
iting
in th
e po
pula
tion
livi
ng w
ithi
n 2
m o
f th
e pl
ant
Dia
rrhe
a w
as th
e on
lysy
mpt
om f
or w
hich
ther
e w
ere
unif
orm
rep
orts
thro
ugho
ut th
e re
port
ing
peri
od i
ncre
asin
g fr
om 4
1
befo
re th
e pl
ant o
pene
d to
76
a
fter
the
plan
t ope
ned
The
re w
ere
no in
crea
ses
in th
e is
olat
ion
ofP
seud
omon
as S
alm
onel
la o
r pa
rasi
tes
in f
ecal
sam
ples
afte
r th
e pl
ant o
pene
d a
nd a
sig
nifi
cant
dec
reas
e in
Pro
teus
isol
atio
ns w
ere
obse
rved
dur
ing
the
oper
atio
nal
peri
od I
ncre
ases
in S
trep
toco
ccus
and
Sta
phyl
ococ
cus
isol
ates
in th
roat
sw
abs
wer
e ob
serv
ed a
fter
pla
ntop
enin
g b
ut r
egre
ssio
n an
alys
es f
ound
no
rela
tion
ship
wit
h ex
posu
re to
the
plan
t S
imil
arly
the
re w
ere
incr
ease
s in
vir
us is
olat
es in
fec
al s
ampl
es d
urin
g th
eop
erat
iona
l pe
riod
but
thos
e in
crea
ses
wer
e no
t fou
ndto
be
rela
ted
to th
e pl
ant
Ant
ibod
y te
sts
for
ente
ric
viru
ses
foun
d no
evi
denc
e of
incr
ease
d ex
posu
re fr
omth
e pl
ant
and
aero
sol m
onit
orin
g re
sult
s in
dica
ted
that
leve
ls
John
son
et a
l 19
80
Jaku
bow
ski
1986
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
110
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
of m
icro
orga
nism
s in
the
air
in th
e re
side
ntia
lar
eas
in th
e vi
cini
ty o
f th
e pl
ant w
ere
sim
ilar
toba
ckgr
ound
con
cent
rati
ons
Pro
spec
tive
Eig
ht-m
onth
hea
lth
surv
ey o
f a
popu
lati
on(n
=2
378)
livi
ng in
the
vici
nity
of
a pl
ant i
nS
koki
e I
L A
naly
ses
of b
lood
thr
oat
and
feca
lsp
ecim
ens
wer
e te
sted
in s
ubse
ts o
f th
epo
pula
tion
Mic
robi
al a
eros
ol m
onit
orin
g an
dm
eteo
rolo
gica
l da
ta w
ere
also
col
lect
ed
Reg
ress
ion
anal
yses
per
form
ed b
etw
een
tota
lpa
rtic
le e
xpos
ure
indi
ces
and
self
-rep
orte
dill
ness
rat
es p
atho
geni
c ba
cter
ia is
olat
ion
rate
spr
eval
ence
rat
es o
f vi
rus
anti
body
and
vir
usan
tibod
y tit
ers
wer
e ne
gativ
e R
egre
ssio
nan
alys
es w
ere
also
neg
ativ
e w
hen
illne
ss r
ates
and
expo
sure
indi
ces
wer
e ru
n w
ith
refe
renc
e to
leng
th o
f re
side
nce
age
sm
okin
g p
rese
nce
ofyo
ung
chil
dren
chr
onic
res
pira
tory
dis
ease
and
chro
nic
gast
roin
test
inal
illn
ess
Nor
thro
p et
al
1980
Ja
kubo
wsk
i 19
86
Sew
age
Tre
atm
ent P
lant
Wor
kers
Cro
ss-s
ecti
onal
Hea
lth
surv
ey o
f w
orke
rs a
t a s
ewag
e tr
eatm
ent
plan
t in
Tor
onto
Can
ada
(n=
50)
Lun
g fu
ncti
onte
sts
and
anal
yses
of
PC
Bs
in b
lood
sam
ples
wer
e al
so c
ondu
cted
(T
he p
lant
rec
eive
dco
ntro
lled
dis
char
ges
of P
CB
s fr
om a
nel
ectr
ical
man
ufac
turi
ng c
ompa
ny)
The
mos
t com
mon
sym
ptom
s re
port
ed b
yw
orke
rs in
clud
ed c
ough
spu
tum
pro
duct
ion
whe
ezin
g s
ore
thro
at a
nd s
kin
com
plai
nts
Wor
kers
tend
ed to
hav
e sl
ight
ly r
educ
ed lu
ngfu
ncti
on S
erum
con
cent
rati
ons
of P
CB
s co
uld
not b
e re
late
d to
sym
ptom
s or
cli
nica
l fin
ding
s
Net
herc
ott a
nd H
olne
ss 1
988
Cro
ss-s
ectio
nal
A s
aliv
a te
st w
as u
sed
to d
etec
t ant
ibod
ies
tohe
patit
is A
vir
us (
anti-
HA
V)
in w
orke
rs a
tw
aste
wat
er p
lant
s se
rvin
g C
olum
bus
OH
(n=
163)
Res
ults
wer
e
For
ty-t
wo
was
tew
ater
wor
kers
and
17
cont
rol
wor
kers
test
ed p
ositi
vely
for
ant
i-H
AV
Aft
erco
ntro
llin
g fo
r co
nfou
ndin
g ef
fect
s of
age
and
race
no
asso
ciat
ion
was
fou
nd b
etw
een
was
tew
ater
wor
k an
d an
incr
ease
d pr
eval
ence
of
anti-
HA
V (
prev
a
Tro
ut e
t al
2000
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
111
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Stu
dy T
ype
End
Poi
nts
Eva
luat
edF
indi
ngs
Ref
eren
ces
com
pare
d w
ith
thos
e fr
om w
orke
rs n
ot e
xpos
edto
was
tew
ater
(n=
139)
le
nce
rati
o=1
3 9
5 c
onfi
denc
e in
terv
al 0
7 to
24)
In
an e
valu
atio
n of
was
tew
ater
wor
kers
alon
e n
o st
atis
tica
lly
sign
ific
ant o
ccup
atio
nal
risk
fact
ors
for
anti
-HA
V w
as f
ound
C
ross
-sec
tion
alW
orke
rs (
n=34
) fr
om e
ight
sew
age
trea
tmen
tpl
ants
in S
wed
en c
ompl
eted
hea
lth
ques
tion
nair
esan
d un
derw
ent
spir
omet
ry a
nd a
irw
ay te
sts
Res
ults
wer
e co
mpa
red
wit
h th
ose
of n
onse
wag
ew
orke
rs (
n=35
)
Rep
orts
of
nasa
l irr
itat
ion
tire
dnes
s a
nd d
iarr
hea
wer
e si
gnif
ican
tly
high
er in
sew
age
wor
kers
com
pare
d w
ith
cont
rols
Air
way
res
pons
iven
ess
was
incr
ease
d am
ong
sew
age
wor
kers
but
ther
ew
ere
no d
iffe
renc
es in
spi
rom
etry
res
ults
The
auth
ors
sugg
este
d th
at th
e sy
mpt
oms
wer
e li
kely
caus
ed b
y en
doto
xin
whi
ch w
as d
etec
ted
betw
een
38
and
321
70ng
m3
Ryl
ande
r 19
99
Cro
ss-s
ecti
onal
Wor
kers
(n=
189)
fro
m 1
6 se
wag
e tr
eatm
ent
plan
ts in
New
Yor
k w
ere
surv
eyed
for
wor
king
habi
ts l
ife
styl
e a
nd s
ympt
oms
of il
lnes
s R
esul
tsw
ere
com
pare
d w
ith
wor
kers
at a
wat
er tr
eatm
ent
plan
t (n=
82)
The
fre
quen
cy o
f he
adac
he d
izzi
ness
sor
e th
roat
sk
in ir
rita
tion
and
dia
rrhe
a w
as s
igni
fica
ntly
high
er a
mon
g th
e se
wag
e w
orke
rs
Sca
rlet
t-K
ranz
et a
l 19
87
Cro
ss-s
ectio
nal
Pat
ient
s (n
=5)
rep
airi
ng a
dec
ante
r fo
r se
wag
esl
udge
con
cent
ratio
n de
velo
ped
illne
sses
cons
iste
nt w
ith
Pont
iac
feve
r
Ser
olog
ical
con
firm
atio
n of
Pon
tiac
fev
er in
all
five
wor
kers
and
rec
over
y of
Leg
ione
lla
pneu
mop
hila
fro
m s
ewag
e sl
udge
Gre
gers
en e
t al
1999
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
112
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Cro
ss-s
ectio
nal
Was
tew
ater
wor
kers
(n=
359)
and
dri
nkin
g-w
ater
wor
kers
(n=
89)
wer
e ex
amin
ed f
or a
nti-
HA
V
Ant
i-H
AV
was
det
ecte
d in
28
4 o
f w
aste
wat
erw
orke
rs a
nd in
23
6 o
f dr
inki
ng-w
ater
wor
kers
A
fter
adj
ustm
ent f
or a
ge a
nd o
ther
var
iabl
es t
heod
ds r
atio
for
ant
i-H
AV
was
2 (
CI
1ndash3
8)
Add
itio
nal r
isk
fact
ors
incl
uded
yea
rs in
indu
stry
ne
ver
wea
ring
fac
e pr
otec
tion
and
ski
n co
ntac
t
Wel
don
et a
l 20
00
Cro
ss-s
ecti
onal
Stu
dy o
f em
ploy
ees
in w
ater
and
sew
age
com
pany
(n=
241)
E
xpos
ure
to r
aw s
ewag
e w
as a
ris
k fa
ctor
for
HA
Vin
fect
ion
(odd
s ra
tio
37
(CI
15
ndash94
) 6
0 o
fw
orke
rs r
epor
ting
exp
osur
e to
raw
sew
age
had
HA
V in
fect
ion
Bru
gha
et a
l 19
98
Cro
ss-s
ecti
onal
Uri
ne a
ssay
for
pes
tici
de a
mon
g w
aste
wat
er tr
eatm
ent
wor
kers
pro
cess
ing
effl
uent
fro
m p
esti
cide
pla
nt a
ndam
ong
com
pari
son
wor
kers
in w
ater
sys
tem
69
of e
xpos
ed w
orke
rs e
xcee
ded
urin
e cu
t-of
fva
lue
com
pare
d w
ith
10
in c
ompa
riso
n pl
ant
Shi
ft c
hang
es w
ere
cons
iste
nt w
ith
occu
pati
onal
expo
sure
Eli
a et
al
1983
Cro
ss-s
ecti
onal
Exa
min
atio
n of
sew
age
trea
tmen
t pla
nt w
orke
rs(n
=14
5) a
fter
hex
achl
oroc
yclo
-pen
tadi
ene
was
dum
ped
into
a m
unic
ipal
sew
age
syst
em
Exa
min
atio
n of
41
empl
oyee
s sh
owed
pro
tein
uria
and
incr
ease
d se
rum
lact
ic d
ehyd
ogen
ase
leve
ls 3
daf
ter
the
plan
t was
clo
sed
The
se f
indi
ngs
wer
e no
tfo
und
3 w
k la
ter
Mor
se e
t al
1979
Pro
spec
tive
Tw
elve
-mon
th s
tudy
of
infe
ctio
n ra
tes
in e
xper
ienc
edan
d in
expe
rien
ced
wor
kers
(n=
336)
exp
osed
tow
aste
wat
er a
nd n
onex
pose
d w
orke
rs in
Cin
cinn
ati
Chi
cago
and
Mem
phis
No
sign
ific
ant
diff
eren
ces
wer
e fo
und
in il
lnes
sra
tes
by w
orke
r ca
tego
ry o
r ci
ty i
n vi
rus
orba
cter
ial i
sola
tion
rat
es o
r in
ser
olog
ical
ana
lyse
sH
ighe
r ra
tes
of g
astr
oint
esti
nal
illn
ess
wer
e re
port
edby
inex
peri
ence
d w
orke
rs b
ut c
ould
not
be
rela
ted
to a
spe
cifi
c ag
ent o
r ex
posu
re
Cla
rk e
t al
1980
Ja
kubo
wsk
i 19
86
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
113
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Stu
dy T
ype
End
Poi
nts
Eva
luat
edF
indi
ngs
Ref
eren
ces
Sero
logi
cal a
naly
sis
for
rota
viru
s N
orw
alk
agen
t an
d P
roto
thec
a w
icke
rham
ii f
rom
seru
m a
rchi
ved
from
the
wor
ker
popu
lati
onab
ove
No
asso
ciat
ion
betw
een
was
tew
ater
exp
osur
ean
d an
tibo
dies
to e
ithe
r ro
tavi
rus
or P
roto
thec
aIn
expe
rien
ced
wor
kers
had
hig
her
leve
ls o
fan
tibo
dies
to N
orw
alk
agen
tE
valu
atio
n of
815
dea
th c
erti
fica
tes
from
form
er w
aste
wat
er w
orke
rs in
Chi
cago
D
eath
s fr
om le
ukem
ia (
p=0
04)
and
pneu
mon
ia(p
=0
02)
wer
e gr
eate
r th
an e
xpec
ted
Cro
ss-s
ecti
onal
Com
pari
son
of p
roto
zoan
par
asit
ic in
fect
ion
amon
g se
wer
wor
kers
(n=
126)
in F
ranc
eco
mpa
red
wit
h 36
3 fo
od h
andl
ers
(n=
363)
Rat
es o
f in
fect
ion
wer
e hi
gher
am
ong
sew
erw
orke
rs f
or a
ll 6
yr F
orei
gn tr
avel
was
cons
ider
ed b
ut n
o ot
her
poss
ible
dif
fere
nces
wer
e fo
und
amon
g ex
pose
d an
d co
mpa
riso
ngr
oups
Sch
loss
er e
t al
1999
Ret
rosp
ecti
veH
isto
rica
l coh
ort s
tudy
of
was
tew
ater
trea
tmen
t wor
kers
(n=
242)
and
com
pari
son
grou
p of
col
lege
mai
nten
ance
wor
kers
(n=
54)
follo
wed
for
12
mo
Sig
nifi
cant
ly h
ighe
r pr
eval
ence
of
gast
roen
teri
tis
and
gast
roin
test
inal
sym
ptom
s (p
lt0
05)
and
head
ache
s (p
lt0
05)
but n
ot re
spir
ator
ysy
mpt
oms
No
diff
eren
ce w
as f
ound
bet
wee
nhi
gh a
nd lo
w e
xpos
ure
cate
gori
es
Khu
der
et a
l 19
98
Cro
ss-s
ectio
nal
Hea
lth
surv
ey a
nd c
lini
cal t
ests
of w
orke
rs a
tsi
x se
wag
e tr
eatm
ent p
lant
s (n
=19
9) in
Sw
eden
com
pare
d w
ith
cont
rol w
orke
rs a
t adr
inki
ng w
ater
pla
nt (
n=41
)
Rep
orts
of
skin
dis
orde
rs d
iarr
hea
and
oth
erga
stro
inte
stin
al s
ympt
oms
wer
e si
gnif
ican
tly
grea
ter
amon
g th
e se
wag
e-tr
eatm
ent
wor
kers
No
diff
eren
ces
wer
e fo
und
in w
hite
-blo
od-c
ell
coun
tor
ser
um I
g co
ncen
trat
ions
bet
wee
n th
e gr
oups
ex
cept
for
sli
ghtl
y in
crea
sed
IgM
con
cent
rati
ons
amon
g
Lun
dhol
m a
nd R
ylan
der
1983
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
114
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
sew
age
wor
kers
The
mos
t lik
ely
caus
e of
sym
ptom
sw
as to
xins
fro
m g
ram
-neg
ativ
e ba
cter
ia
Cro
ss-s
ecti
onal
Wor
kers
in s
ewag
e tr
eatm
ent p
lant
(n=
30)
com
pare
d w
ith
age-
mat
ched
blo
od d
onor
sE
nvir
onm
enta
l m
easu
rem
ent
of d
ust a
nd a
irbo
rne
bact
eria
con
duct
ed E
leva
tion
s in
IgA
thr
ombo
cyte
sle
ukoc
ytes
end
otox
in a
ntib
odie
s c
-rea
ctiv
e pr
otei
nsco
nsid
ered
con
sist
ent w
ith
endo
toxi
n ex
posu
re
Ryl
ande
r et
al
1977
Com
post
Wor
kers
Cro
ss-s
ecti
onal
Hea
th c
ompl
aint
s an
d di
seas
es o
f co
mpo
st w
orke
rs(n
=58
) in
Ham
burg
Ger
man
y co
mpa
red
wit
hco
ntro
l sub
ject
s (n
=40
)
Sig
nifi
cant
ly m
ore
sym
ptom
s an
d di
seas
es o
f th
eai
rway
s (p
=0
003)
and
ski
n (p
=0
02)
wer
e re
port
edby
com
post
wor
kers
than
con
trol
s A
ntib
ody
conc
entr
atio
ns to
fun
gi a
nd a
ctin
omyc
etes
wer
esi
gnif
ican
tly
incr
ease
d in
com
post
wor
kers
Buumln
ger
et a
l 20
00
Pro
spec
tive
Infe
ctio
n ra
tes
amon
g co
mpo
st w
orke
rs in
Cam
den
NJ
Phi
lade
lphi
a P
A B
elts
vill
e M
D a
ndW
ashi
ngto
n D
C w
ith
high
exp
osur
e (n
=98
) an
din
term
edia
te e
xpos
ure
(n=
157)
and
wor
kers
not
invo
lved
in c
ompo
stin
g (n
=13
3) S
tudy
per
iod
was
betw
een
1979
and
198
1
Eye
and
ski
n ir
rita
tion
was
rep
orte
d m
ore
freq
uent
lyam
ong
com
post
-exp
osed
gro
ups
Asp
ergi
llus
fum
igat
us w
as d
etec
ted
in n
asal
and
thro
at s
wab
s(7
0 in
hig
h-ex
posu
re g
roup
20
in in
term
edia
te-
expo
sure
gro
up a
nd 5
in
low
-exp
osur
e gr
oup)
but
ther
e w
as n
o co
nsis
tent
incr
ease
in a
ntib
odie
s to
the
fung
al s
pore
s T
here
wer
e no
dif
fere
nces
in le
vels
of
anti
bodi
es to
Leg
ione
lla
pneu
mop
hila
bet
wee
nex
posu
re g
roup
s a
nd n
o an
tibo
dies
to H
isto
plas
ma
caps
ulat
um w
ere
dete
cted
Com
post
wor
kers
had
grea
ter
IgG
ant
ibod
y le
vels
aga
inst
com
post
-der
ived
endo
toxi
n e
leva
ted
C3
and
hem
olyt
ic c
ompl
emen
tle
vels
and
hig
her
whi
te-
Cla
rk e
t al
1984
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
115
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Stu
dy T
ype
End
Poi
nts
Eva
luat
edF
indi
ngs
Ref
eren
ces
bloo
d-ce
ll a
nd e
osin
ophi
lic c
ount
s I
n pu
lmon
ary
func
tion
test
s v
ital f
orce
d ca
paci
ty w
as g
reat
erat
the
end
of th
e w
eek
than
at t
he b
egin
ning
of
the
wee
k fo
r co
mpo
st w
orke
rs
Abb
revi
atio
ns C
I c
onfi
denc
e in
terv
al P
CB
s p
olyc
hlor
inat
ed b
iphe
nyls
VO
Cs
vol
atil
e or
gani
c co
mpo
unds
ppb
par
ts p
er b
illi
on m
met
er n
g n
anog
ram
HA
V
hepa
titi
s A
vir
us I
g im
mun
oglo
buli
n
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
116
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
bull gation conducted before current regulatory requirements for biosolidswere initiated demonstrates the possibility of chemical contaminationfrom biosolids No other studies of farm or nonfarm biosolids users werefound
bull Populations near agricultural application sites One study of apopulation near a biosolids land-application site was found (Dorn et al1985) That study reported no differences in symptoms or serologicalconversion between farm residents living near the application site and acomparison group
bull Workers in biosolids production andor application industry Onestudy by the National Institute for Occupational Safety and Health(NIOSH) reported a history of gastrointestinal illness in workers handlingClass B biosolids (Burton and Trout 1999) Environmental assessmentfound potential worker exposure to enteric bacteria After the study wasissued Lodor (2001) reported that the biosolids to which the workerswere exposed did not meet Class B requirements NIOSH (2002)subsequently released a guidance document for controlling potential risksto workers exposed to Class B biosolids that supercedes its earlier HazardID document on Class B biosolids
bull Populations near sewage treatment plants The committee evaluatedfour studies of populations living near sewage treatment plants Thesestudies cover a wide spectrum of outcomes and exposures and include oneto a few studies of any particular area Increases in gastrointestinal andrespiratory illnesses (Fannin et al 1980) an increase in diarrhea (Camannet al 1980) and decrease in school absenteeism (Camann et al 1980)were reported However these studies are not sufficient to evaluate thesafety of populations near sewage treatment plants
bull Sewage treatment plant workers Fourteen studies of sewage treatmentplant workers were evaluated These studies reported both increases(Brugha et al 1998 Weldon et al 2000) and no increases (Trout et al2000) in hepatitis A infection increased complaints of nasal irritationtiredness and diarrhea which were considered compatible with exposureto endotoxin (Rylander et al 1977) increased prevalence ofgastroenteritis (Khuder et al 1998) a confirmed outbreak of Pontiac fever(Gregersen et al 1999) evidence of pesticide absorption (Elia et al1983) no differences in illnesses rates nor isolation of virus or bacteria(Clark et al 1984) increased rates of protozoan infection (Scholsser et al1999) and increased rates of reports of skin disorders diarrhea andgastrointestinal symptoms (Lundholm and Rylander 1983) These studiesare sufficient to suggest transmission of specific infectious diseases tosewage treatment plant workers (eg Pontiac Fever) However no firmconclusions can be drawn at this time
bull Compost workers Studies of compost workers have reported significantincreases in diseases of the airways and skin and evidence of increased
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exposure to fungi and actinomycetes (Buumlnger et al 2000) and eye andskin irritation and fungal colonization but no serological evidence ofinfection (Clark et al 1984) These two studies provide suggestiveevidence of colonization of compost workers with fungi
Observed Health Outcomes
bull Toxic exposures Two studies (Baker et al 1980 Morse et al 1979)documented the potential for industrial chemicals to be present inwastewater Sewage workers can be exposed as can those who usebiosolids for agriculture or other land-application purposes Morse et al(1979) investigated occupational exposure resulting from a one-timecontamination of the wastewater and Baker et al (1980) studiedoccupational and residential exposure resulting from an ongoingcontamination of wastewater These two studies demonstrate that workersand community residents can be exposed to chemical hazards that enterinto the municipal waste stream
The epidemiological literature on exposure to toxic substances inbiosolids provides no information by which to gauge two issues The firstissue concerns the adequacy of routine monitoring of wastewater in orderto capture common toxicants and toxicants that might be idiosyncratic tothe industrial processes in a particular locale Although wastewater isperiodically examined for chemical contamination the number ofchemicals sought is much less compared with the number of chemicalsused commercially Second the periodicity of testing and the periodicityof discharge will determine the probability of identification of ahazardous chemical in a sample of effluent
bull Viral infection The potential for viral infection of wastewater workerswas documented in several studies (Brugha et al 1998 Weldon et al2000) and not in others (Clark et al 1980 Northrop et al 1980) Onestudy documented the absence of serological evidence of viral infectionamong populations near application sites (Dorn et al 1985) No studyexamined viral infection among workers in biosolids production orapplication sites
The epidemiological literature provides no evidence for or against thepotential for biosolids to serve as a vehicle for viral infection Theprobability that biosolids are a potential vector for infection might berevealed by other lines of research such as environmental viral studies
bull Bacterial and protozoan infection Some studies have documentedcomplaints of gastrointestinal illness related to sewage sludge (Fannin etal 1980 Johnson et al 1980 Burton and Trout 1999) and others have not(Dorn et al 1985) Similarly some studies have detected enteric bacteriain air and
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bulk samples (Burton and Trout 1999) and others have not (Johnson et al1980) One study found evidence of protozoan infection among sewerworkers (Schlosser et al 1999)
For bacterial and protozoan infection there is neither evidence ofinfection nor evidence of no infection Evidence of viable organisms inbiosolids would strengthen the biological plausibility of a causalassociation as would demonstration of the potential for exposure duringspecific aspects of production and application of biosolids
bull Irritation and allergic reaction Several studies reported allergy orirritation among sewer workers (Rylander 1999) and workers in compostproduction (Clark et al 1984 Buumlnger et al 2000) The role of endotoxinin these observations is strengthened by demonstration of endotoxincontent of biosolids but is weakened by lack of evidence showing arelationship between level of exposure and effect
Assessment of Causality
Assessment of causality requires judgment of epidemiological and otherinformation Conclusions that an association is causal rest on demonstration ofsuch factors as consistency of findings in independent studies strength ofassociation temporal sequence and biological plausibility (demonstration ofdose-response relationships) (Bradford-Hill 1966) There is a small body ofepidemiological literature on the potential adverse health effects of biosolidsThe literature is even more sparse considering the varying populations that arepotentially exposed to biosolids via wastewater treatment biosolids productionoccupational exposure during application and community exposure
For some exposures such as chemical exposure it is fairly clear thatchemical contamination of sewage with industrial chemicals can result inproduct contamination leading to exposure of workers and communityresidents It is unclear whether the system for preventing chemicalcontamination of sewage and monitoring sewage is sufficient to ensureprotection from chemical exposures
Although there is evidence of infection of sewage workers it is unclearbased on design criteria for production of biosolids or based on sampling fordetection of viable organisms whether viral bacterial or protozoal infection ofworkers or community residents exposed to biosolids is plausible There is arelative absence of evidence documenting infection and limited evidencedocumenting the lack of infection from biosolids A similar assessment can bemade for the evidence of a causal relationship of symptoms of irritation andallergy and exposure to endotoxins
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Some have contended that there is evidence of lack of health hazard fromoccupational exposure in wastewater treatment plants and that by extrapolationrisk from biosolids must be negligible This reasoning is problematic for severalreasons First as described earlier in this chapter the knowledge base regardingwastewater treatment workers is thin and contradictory Second the exposurecharacteristics will be quite different in the wastewater treatment industrycompared with biosolids land-application For example potential exposures toairborne contaminants from wet sewage sludge are quite different from thosefrom dried biosolids Third the routes of exposure may be different betweenpopulations exposed to raw sewage sludge compared with those exposed tobiosolids Fourth the populations exposed to biosolids may not be equivalent tothe occupational population exposed to sewage sludge Farm families andcommunity residents will include subpopulations unlikely to be found in theworkplace such as children and individuals with respiratory diseases Thuslack of compelling evidence of adverse health effects among wastewatertreatment workers should not be used to infer that there will be a lack of adversehealth effects from exposure to biosolids
There are two types of health studies that will reduce uncertainty regardinghealth effects of biosolids exposuremdashresponse studies and preplanned studiesResponse studies are initiated rapidly on notification that there has been eitheran unusual exposure or occurrence of disease among workers or communityresidents exposed to biosolids Such studies are intended to assess and attemptto relate measures of exposure with measures of disease Response studiesshould be conducted in a short time frame (weeks to months) Whether responsestudies are conducted by state or federal agencies or academia on behalf ofEPA a priority setting mechanism must be established so that limited resourcesare used to maximize the probability that the response studies will effectivelycontribute to the sparse information on the health consequences of exposure ofworkers andor residents to biosolids during production and manufacture
Preplanned studies on the other hand are conducted to test a specifichypothesis The hypothesis might be generated by researchers who compete forresearch funding or more specific questions may be formed by EPA or otheragencies Preplanned studies must be well designed and conducted to reduceuncertainty concerning issues of importance For example a preplannedepidemiological study must be sufficiently large characterize exposure includean adequate interval between exposure and observation to allow for occurrenceof disease if it were to occur measure confounders and be able to delineateadverse outcomes and evidence of their occurrence
There are two types of preplanned studiesmdashexposure assessment andcomplete epidemiological studies In exposure assessment studies the goal is
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to define the distribution and determinants of exposure to an agent or chemicalof interest This information may then be used in formal risk assessments
The second type of preplanned study is the complete epidemiologicalstudy The goal of this study is to assess the association of the occurrence anddistribution of disease with measurement of prior exposure (provided through aconcurrent or prior exposure assessment) The purpose of preplanned studies isto determine if exposure is related to increased occurrence of disease or itscorollary
In contrast with response studies preplanned studies are more expensivebecause they are larger require more effort in planning and involve moreextensive data analysis and more effort in assessment of exposureConsequently more effort will be expended in setting priorities in preplannedstudies Priorities should include probability of the study reducing uncertaintyseriousness of the disease outcome incidences of the disease outcome a priorilevel of uncertainty and importance of the results in protecting against adversehealth consequences
It is also important to recognize that worker populations and communitiesare not homogenous in their susceptibility to disease or subsequent adverseconsequences Thus in response and preplanned studies it is important toinclude all or a sample of the potentially susceptible subpopulations Examplesof susceptible subpopulations include children the elderly pregnant womenand individuals with chronic disease
In addition stakeholders should be involved in review of the designconduct and interpretation of studies Stakeholders may include representativesof workers and management community representatives health care providersand victims of disease
FINDINGS AND RECOMMENDATIONS
The committee concludes that because of the lack of epidemiological studyand the need to address the publicrsquos concerns about potential adverse healtheffects EPA should conduct studies that examine exposure and potential healthrisks to worker and community populations Studies of wastewater treatmentworkers should not be used as substitutes for studies of actual biosolidsexposure While routine human health surveillance of all populations exposedto biosolids is impractical the committee recommends that EPA promote andsupport a research effort to reduce uncertainty about the possible healthconsequences of exposure to biosolids Stakeholders should be involved inreview of the design conduct and interpretation of studies The committeerecommends the following types of study
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Response Studies
bull Studies in response to unusual exposure and unusual occurrence ofdisease On occasion unplanned events occur that can provideinformation on the agents of disease An example might be an outbreak ora symptom of disease following a known exposure or an unusualexposure scenario In both instances exposure and health outcomesshould be determined
Preplanned Studies
bull Biosolids exposure-assessment studies Such studies should characterizethe exposures of workers such as biosolids appliers and farmers and thegeneral public who come into contact with constituents of biosolids eitherdirectly or indirectly The studies would require identification ofmicroorganisms and chemicals to be measured selection of measurementmethods for field samples and collection of adequate samples inappropriate scenarios A possible exposure-assessment study would be tomeasure endotoxin exposure of workers at biosolids production andapplication sites and of communities nearby
bull Complete epidemiological studies of routine biosolids use These studiesshould be conducted to provide evidence of a causal association or a lackthereof between biosolids exposure and adverse human health effectsThey should include an assessment of the occurrence of disease and anassessment or measurement of potential exposures An example of alongitudinal epidemiological study would be an evaluation of healtheffects in a cohort of biosolids appliers these workers should becharacterized by duration and level of exposure with appropriate follow-up
REFERENCES
Baker Jr EL PJLandrigan CJGlueck MMZack Jr JALiddle VWBurse WJHousworthand LLNeedham 1980 Metabolic consequences of exposure to polychlorinatedbiphenyls (PCB) in sewage sludge Am J Epidemiol 112(4)553ndash563
Bradford-Hill A 1966 The environment and disease Association or causation Proc Royal SocMed 58295ndash300
Brugha R JHeptonstall PFarrington SAndren KPerry and JParry 1998 Risk of hepatits Ainfection in sewage workers Occup Environ Med 55(8)567ndash569
Buumlnger J MAntlauf-Lammers TGSchulz GAWestphal MMMuumlller P Ruhnau andEHallier 2000 Health complaints and immunological markers
EPIDEMIOLOGICAL EVIDENCE OF HEALTH EFFECTS ASSOCIATED WITHBIOSOLIDS PRODUCTION AND APPLICATION
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rigin
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ompo
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from
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es c
reat
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rom
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inal
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er b
ook
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heor
igin
al ty
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tting
file
s P
age
brea
ks a
re tr
ue to
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orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
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hic
erro
rs m
ay h
ave
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his
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thor
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e ve
rsio
n fo
r attr
ibut
ion
of exposure to bioaerosols among biowaste collectors and compost workers OccupEnviron Med 57(7)458ndash464
Burton NC and DTrout 1999 NIOSH Health Hazard Evaluation Report BioSolids LandApplication Process LeSourdsville Ohio HETA 98ndash0118ndash2748 US Department ofHealth and Human Services Public Health Service Centers for Disease Control andPrevention National Institute for Occupational Safety and Health Cincinnati OH
Camann DE HJHarding and DEJohnson 1980 Wastewater aerosol and school attendancemonitoring at an advanced wastewater treatment facility Durham Plant Tigard OregonPp 160ndash179 in Wastewater Aerosols and Disease Proceedings of A SymposiumSeptember 19ndash21 1979 HRPahren and W Jakubowski eds EPA-6009ndash80ndash028 NTISPB81ndash169864 Health Effects Research Laboratory Office of Research and DevelopmentUS Environmental Protection Agency Cincinnati OH
Clark CS HSBjornson JSchwartz-Fulton JWHolland and PSGartside 1984 Biologicalhealth risks associated with the composting of wastewater treatment plant sludge J WaterPoll Control Fed 56(12)1269ndash1276
Clark CS GLVan Meer CCLinnemann ABBjornson PSGartside GM Schiff SETrimbleDAlexander EJCleary and JPPhair 1980 Health effects of occupational exposure towastewater Pp 239ndash264 in Wastewater Aerosols and Disease Proceedings of ASymposium September 19ndash21 1979 HRPahren and WJakubowski eds EPA-6009ndash80ndash028 NTIS PB81ndash169864 Health Effects Research Laboratory Office of Research andDevelopment US Environmental Protection Agency Cincinnati OH
Dorn CR CSReddy DNLamphere JVGaeuman and RLanese 1985 Municipal sewagesludge application on Ohio farms Health effects Environ Res 38(2)332ndash359
Elia VJ CSClark VAMajeti PSGartside TMacDonald NRichdale CR Meyer GLVanMeer and KHunninen 1983 Hazardous chemical exposure at a municipal wastewatertreatment plant Environ Res 32(2)360ndash371
Fannin KF KWCochran DELamphiear and ASMonto 1980 Acute illness differences withregard to distance from the Tecumseh Michigan Wastewater Treatment Plant Pp 117ndash135 in Wastewater Aerosols and Disease Proceedings of A Symposium September 19ndash211979 HRPahren and WJakubowski eds EPA-6009ndash80ndash028 NTIS PB81ndash169864Health Effects Research Laboratory Office of Research and Development USEnvironmental Protection Agency Cincinnati OH
Gregersen P KGrunnet SAUldum BHAndersen and HMadsen 1999 Pontiac fever at asewage treatment plant in the food industry Scand J Work Environ Health 25(3)291ndash295
Jakubowski W 1986 US EPA-sponsored epidemiological studies of health effects associated withthe treatment and disposal of wastewater and sewage sludge Pp 140ndash153 inEpidemiological Studies of Risks Associated with the Agricultural Use of Sewage SludgeKnowledge and Needs JCBlock AHHavelaar and P LrsquoHermite eds New York NYElsevier Applied Science Publishers
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from
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es c
reat
ed f
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inal
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er b
ook
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heor
igin
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pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
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iden
tally
inse
rted
Ple
ase
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sion
of t
his
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icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Johnson DE DECamann JWRegister RJPrevost JBTillery REThomas JMTaylor andJMHosenfeld 1980 Health effects from wastewater aerosols at a new activated sludgeplant John Egan Plant Schaumburg Illinois Pp 136ndash 159 in Wastewater Aerosols andDisease Proceedings of A Symposium September 19ndash21 1979 HRPahren andWJakubowski eds EPA-6009ndash80ndash028 NTIS PB81ndash169864 Health Effects ResearchLaboratory Office of Research and Development US Environmental Protection AgencyCincinnati OH
Khuder SA TArthur MSBisesi and EASchaub 1998 Prevalence of infectious diseases andassociated symptoms in wastewater treatment workers Am J Ind Med 33(6)571ndash577
Lodor ML 2001 NIOSH reports omits significant details in LeSourdsville case BiosolidsTechnical Bulletin 7(4)11ndash13
Lundholm M and RRylander 1983 Work related symptoms among sewage workers Br J IndMed 40(3)325ndash329
Morse DL JRKominsky CLWisseman III and PJLandrigan 1979 Occupational exposure tohexachlorocyclopentadiene How safe is sewage JAMA 241(20)2177ndash2179
Nethercott JR and DLHolness 1988 Health status of a group of sewage sludge treatmentworkers in Toronto Canada Am Ind Hyg Assoc J 49(7)346ndash350
NIOSH (National Institute for Occupational Safety and Health) 2002 Guidance for ControllingPotential Risks to Workers Exposed to Class B Biosolids DHHS (NIOSH) 2002ndash149National Institute for Occupational Safety and Health Centers for Disease Control andPrevention Public Health Service US Department of Health and Human ServicesPreprint June 12 2002
Northrop R BCarnow RWadden SRosenberg ANeal LSheaff JHolden S Meyer andPScheff 1980 Health effects of aerosols emitted from an activated sludge plant Pp 180ndash227 in Wastewater Aerosols and Disease Proceedings of A Symposium September 19ndash211979 HRPahren and WJakubowski eds EPA-6009ndash80ndash028 NTIS PB81ndash169864Health Effects Research Laboratory Office of Research and Development USEnvironmental Protection Agency Cincinnati OH
Rylander R 1999 Health effects among workers in sewage treatment plants Occup Environ Med56(5)354ndash357
Rylander R KAndersson LBelin GBerglund RBergstrom LHanson M Lundholm andIMattsby 1977 Studies on humans exposed to airborne sewage sludge Schweiz MedWochenschr 107(6)182ndash184
Scarlett-Kranz JM JGBabish DStrickland and DJLisk 1987 Health among municipal sewageand water treatment workers Toxicol Ind Health 3(3)311ndash 319
Schlosser O DGrall and MNLaurenceau 1999 Intestinal parasite carriage in workers exposedto sewage Eur J Epidemiol 15(3)261ndash265
Trout D CMueller LVenczel and AKrake 2000 Evaluation of occupational transmission ofhepatitis A virus among wastewater workers J Occup Environ Med 42(1)83ndash87
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setti
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ay h
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Weldon M MJVanEgdom KAHendricks GRegner BPBell and LMSehulster 2000Prevalence of antibody to hepatitis A virus in drinking water workers and wastewaterworkers in Texas from 1996 to 1997 J Occup Environ Med 42(8)821ndash826
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4
Advances in Risk Assessment Since theEstablishment of the Part 503 Rule
The committeersquos review of the risk assessment used to support the Part503 rule was carried out in the context of current and emerging practice in riskassessment The committee determined that its review of the risk assessmentshould communicate the committeersquos interpretation of how the risk-assessmentprocess has evolved from the time the Part 503 rule was issued until present Ofparticular interest to the committee were documents from EPA and the NationalResearch Council (NRC) that propose and encourage methods that differsubstantially from the methods used in the Part 503 risk assessment Thischapter provides a foundation and context for the following chapters
This chapter first describes new approaches and considerations in riskassessment since the Part 503 rule (Standards for Use or Disposal of SewageSludge) was established in 1993 (40 CFR Part 503) It focuses on the changingpriorities of cancer versus noncancer end points acute versus chronic endpoints probabilistic risk-assessment approaches and the need to addressaggregate exposures and cumulative risk A brief description is then given ofthe changes in risk-assessment approaches of EPA over this period
THE RISK-ASSESSMENT PROCESS
Risk assessment is a process for identifying potential adverseconsequences along with their severity and likelihood In contrast to other tools
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used for environmental evaluation and policy the principal objective of the riskassessment and risk management approach is not to eliminate all risk but toquantify the risk and provide risk managers with tools to balance the level ofrisk against the cost of risk reduction against competing risks or against risksthat are generally accepted as trivial or acceptable Controlling the exposure ofhuman populations to environmental contaminants in biosolids using a risk-based approach requires a definition of both an appropriate metric for assessingthe impacts of contaminants on human health and a defensible process forassigning value to the predicted impacts The end product of a risk-basedapproach to environmental management is either to identify an acceptable levelof exposure or to prescribe the technical controls or political process needed toattain acceptable risk Intervention can be achieved through technical orpolitical controls
Components of the Risk-Analysis Process
The NRC (1982 1994) has divided and continues to divide the practice ofrisk analysis into two substantially different processesmdashrisk assessment andrisk management Along with these processes are concurrent efforts tocommunicate and evaluate risk (NRC 1989 1996) This section explores theevolution of the risk-assessment process over the last decade by considering thecomponent steps in the process
Risk assessment is the process of selecting and quantifying the adverseconsequences that result from an action such as application of biosolids tosoils or from inaction A risk assessment begins with efforts to identify thepotential hazards associated with a chemical or microbial agent and its use oroccurrence Hazard identification addresses the potential for harm but not thelikelihood of harm Risk characterization establishes the significance of anidentified hazard by quantifying the likelihood and severity of exposurescenarios linked to that hazard As applied to toxic agents risk characterizationhas five principal elements (1) quantification of sources and environmentalconcentrations in exposure media (2) quantification of exposure to the targetpopulation and distribution of the dose among the population (3)characterization of a dose-response function for all potential toxic agents thathave been identified (4) estimates of the number of people affected andseverity of consequences expected within the population at risk and (5) anassessment of the magnitude and sources of uncertainty that limit the precisionof the estimate of consequences
Risk management is the process of weighing policy alternatives andselecting the appropriate societal or institutional response Risk management is
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used to integrate the results of a risk characterization with social economic andpolitical valuation to reach a decision The goal of the risk-management processis to establish the significance of the estimated risk compare the costs ofreducing this risk with the benefits gained compare the estimated risks with thesocietal benefits derived from incurring the risk and carry out the political andinstitutional process of reducing risk
Linking the risk-assessment and risk-management processes are theconcurrent efforts to evaluate and communicate risk Risk evaluation is theprocess by which the risk-characterization and risk-management processes arereconciled with individual and societal valuations of risk (NRC 1996) A keystep in this link is effective risk communication According to the NRC (1989)risk communication has become more difficult in recent decades and commonmisconceptions often hamper communication efforts In considering theseissues the NRC (1989) emphasizes that solving the problems of riskcommunication is as much about improving procedures as improving thecontent of risk messages
Figure 4ndash1 provides a view of how the risk-analysis process might proceedfor assessing the health impacts of pollutants in biosolids Each of the majorsteps in this process involves one or more actions that are listed to the right ofeach major step
Confronting Uncertainty and Variability
An important and often ignored final step in the risk characterizationprocess is the characterization of uncertainties Important sources of uncertaintyand variability in risk assessments involve the data and models used Withincomplete data and models used to characterize contaminant transportrepresenting heterogeneous geographic and climate regions the variability anduncertainty associated with the resulting risk estimates are large
In evaluations of uncertainty in risk assessment Morgan et al (1990) andFinkel (1990) distinguish among parameter uncertainty model uncertaintydecision-rule uncertainty and natural variability in any of the parameters andcall for separate treatment of the different types of uncertainty Probabilisticmethods such as Monte Carlo analysis are available to evaluate uncertainty inparameters According to Finkel (1990) model uncertainty derives from anumber of actions including the use of simplifications that might excluderelevant variables from the analysis the use of surrogate variables that mightnot be appropriate for the variable of interest the appearance of abnormalconditions that might occur in nature but that might not be appropriate in themodel and the use of incorrect model forms Morgan et al (1990) noted that
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FIG
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E 4
ndash1 T
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relatively little research has been done on uncertainty or disagreementabout what form of model to use Decision-rule uncertainty applies to riskmanagement and arises whenever ambiguity or controversy exists aboutquantifying or comparing social objectives According to Finkel (1990 p 16)ldquoto take any actions using the outputs of a risk assessment including thedecision not to take action one must be prepared to make a series of potentiallycontroversial value judgmentsrdquo
An important source of uncertainty in risk characterization is thedevelopment and application of dose-response models Among the many issuesthat complicate the process of establishing a dose-response function is thevariation in human susceptibility In large heterogeneous populations there arelarge variations in susceptibility to toxic effects Those variations are due in partto variations in genetic predisposition to certain disease states variations in ageand large variations in physical stresses and other chemical or non-chemicalexposures that might be extant in the system of interest
NEW APPROACHES AND CONSIDERATIONS IN RISKASSESSMENT
This section reviews new approaches to risk assessment that weredeveloped since the Part 503 rule was issued A summary of key documentsfrom the NRC the PresidentialCongressional Commission on Risk Assessmentand Risk Management and EPA are provided Then consideration is given tohow those documents have altered the standard practice in each of the key stepsof the risk-assessment process
Recent Reports Define New Directions in Risk Assessment
Among the reports that have had particular impact are two reports issuedby the NRC The first report titled Science and Judgment in Risk Assessmentprovided an update on the process of risk assessment and management (NRC1994) This report made seventy-five specific recommendations but among itsoverarching recommendations are those to address explicitly uncertainty andvariability in risk assessment to address multimedia exposures and cumulativeintake through multiple exposure pathways to and foster more interactionamong risk assessors and risk managers The second report titledUnderstanding Risk Informing Decisions in a Democratic Society (NRC 1996)used several case studies to evaluate the emerging trends in risk-assessmentmethodology
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The PresidentialCongressional Commission on Risk Assessment and RiskManagement was created through the 1990 Clean Air Act amendments to makerecommendations for improving the risk-assessment and risk-managementprocess In 1997 the commission issued Framework for Environmental HealthRisk Management The report emphasizes how to present a risk assessment andhow to work with community concerns in an iterative fashion It identifies aclear need to modify the traditional approaches used to assess and reduce risksTraditional approaches rely on a chemical-by-chemical medium-by-mediumrisk-by-risk strategy The report states the need to focus less attention onrefining assumption-laden mathematical estimates of the small risks associatedwith exposures to specific chemicals and the need to focus instead on theoverall goal of reducing risk and improving health status There is strongemphasis on stakeholder participation Stakeholders are groups who arepotentially affected by the risk groups who will manage the risk and groupswho will be affected by efforts to manage the source of the risk Involvingstakeholders throughout the risk-assessment process provides opportunities togather information and to bridge gaps in understanding language values andperspectives
Over the last decade EPA issued a number of reports that are having animpact on the framework and process of regulatory risk assessment Ofparticular note are the 1992 Habicht memo which provides guidance to EPAmanagers on risk characterization (Habicht 1992) a journal report onbenchmark dose (Barnes et al 1995) which provides guidance for a moreharmonized approach for addressing cancer and noncancer health end pointsand the proposed guidelines for carcinogen risk assessment (EPA 1996a) TheHabicht memo emphasizes the need to avoid point estimates of risk and toprovide instead details on the scientific basis of decisions including clearstatement of assumptions and uncertainties Barnes et al (1995) recommend theuse of the benchmark-dose approach as an alternative to using the no-observed-adverse-effect level EPArsquos proposed guidelines for carcinogen risk assessmentput more emphasis on ldquomargin of exposurerdquo (relative to a benchmark dose)weight of evidence and the use of uncertainty factors in the riskcharacterization process Also of note is EPArsquos (1997a) Exposure FactorsHandbook which provides a large compendium of information on humanactivities that relate to exposuremdashincluding time-activity data exposureduration consumption of homegrown food and water ingestion
In addition there is an ongoing effort to address aggregate exposures to thesame substances from multiple sources and pathways and cumulative exposuresand risk from mixtures The 1996 Food Quality Protection Act (FQPA)explicitly calls for addressing aggregate exposure and cumulative risk in settingstandards for pesticide residues in food
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From a risk assessment perspective this report will clearly establish thatbiosolids are a complex mixture of chemical and biological agents the exactcomposition of which can change from time to time and place to placeMoreover it will never be possible to account for all the components of themixture although the stable components are well characterized As discussed indetail in various sections of this report considerable effort has been devoted toan enumeration of the hazardous constituents of biosolids During the course ofits study the committee found that it remains necessary to conduct riskassessments on biosolids based on their component parts
Figure 4ndash2 provides a time line showing when a number of significant risk-guidance documents have been issued relative to the year when the Part 503rule was issued
Advances in Hazard Identification
Since EPA issued cancer and mutagenicity risk-assessment guidelines in1986 (EPA 1986ac) the types and reliability of methods used to identifypotential hazard have advanced In the 1986 guidelines the stated goal of ahazard assessment was to provide a review of the relevant biological andchemical information on an agent that might pose cancer or other healthhazards At that time the recommended elements of the hazard identificationincluded (1) a summary of an agentrsquos physical-chemical properties and routesand patterns of exposure and (2) a review of toxic effects structure-activityindicators of toxicity metabolic and pharmacokinetic properties short-termanimal and cell tests long-term animal tests and human studies Theseelements have remained the core components of hazard identification but thearsenal of methods the reliability of techniques and the relative emphasis onthe various hazard identification elements have changed over the past decade Inparticular risk assessors can now make use of better markers of genetic damage(toxicogenomics) for rapid assessment improved structure-activityrelationships (SAR) and improved quantitative structure-activity relationships(QSAR) However to date these emerging methods have seen only limited usein regulatory risk assessment Health-effects research has focused more on earlyindicators of outcome making it possible to shorten the time between exposureand observation of an effect Use of measures of exposure as hazard indicators(eg Hertwich et al 2001) has increased and more-sophisticated measures ofhazard such as the human toxicity potential have been developed Humantoxicity potential includes emissions exposure potential and toxic hazardindicators in a single measure of potential harm It has been used as acumulative-exposure screening tool for multiple chemical agents
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FIG
UR
E 4
ndash2 T
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art 5
03 r
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Public-health and environmental concerns about biosolids foster a need forhazard assessments that can address multiple and complex issues Among theseissues are health hazards from chemical mixtures and pathogens as well asconcerns about specific categories of chemical hazard such as metals persistentorganic pollutants (POPs) and high-production-volume chemicals (HPVs)Recent advances in hazard assessment provide EPA with better tools for thoseissues Community issues are not adequately addressed in the current risk-assessment paradigm (eg property intrusions odor and truck traffic) Otherissues have been addressed in EPA programs but have not been explicitlyaddressed in the risk-management goals of the biosolids program Thoseinclude potential health effects from added diesel exhaust and potentialenvironmental effects from added nitrogen burdens runoff damage toendangered species habitat and conversion of inorganic mercury to organicmercury in situ and in water bodies following runoff
Advances in the Dose-Response Characterization Process
A number of important changes have been proposed and in some casesapplied to dose-response characterization over the last decade In 1993 theNRC considered the scientific basis inference assumptions regulatory usesand research needs in risk assessment and focused on two dose-response issuesmdashthe use of maximum tolerated dose in animal bioassays and the use of two-stage models of carcinogenesis (NRC 1993) The report presented options forrevising those default procedures Recent EPA documents (EPA 1996a 2001a)proposed that dose-response characterization be handled differently from thatproposed in the 1986 risk-assessment guidelines (EPA 1986a) According to the1986 guidelines risk for carcinogens is modeled using potencymdashthe increase ofrisk per unit increase of dose or exposure Risk for noncarcinogens is addressedusing a hazard indexmdashthe ratio of the predicted dose to the reference doseMore recently efforts have been made to harmonize those two approaches byusing a margin of exposure (MOE) to characterize risk for both carcinogens andnoncarcinogens MOE is the ratio of a dose derived from a tumor bioassayepidemiologic study or biologic marker study to an actual or projected humanexposure
Changes in Dose-Response Methods
Several proposals within and outside EPA have been made to modify thestandard approach for building dose-response models on the basis of animal orhuman data The most important and comprehensive proposal is EPArsquos
ADVANCES IN RISK ASSESSMENT SINCE THE ESTABLISHMENT OF THE PART503 RULE
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1996 proposed revisions to its carcinogen risk-assessment guidelines (EPA1996a) These guidelines which are still undergoing review and revision withinEPA propose a different weight-of-evidence classification and the option ofusing an MOE in place of potency to estimate risk Risk-assessment literaturehas provided proposals for the use of time-to-tumor models (Krewski et al1983) Bayesian methods for constructing and revising dose-response models(Taylor et al 1993 Evans et al 1994 Wilson 2001) and meta-analysis
EPArsquos Proposed 1996 Carcinogen Risk-Assessment Guidelines
In 1996 EPA issued its proposed Guidelines for Carcinogen RiskAssessment (EPA 1996a) for a 120-day public review and comment periodEPA issued the guidelines as a replacement for the 1986 Guidelines forCarcinogen Risk Assessment (EPA 1986a) The revised guidelines were issuedin part to address changes in the understanding of the variety of ways in whichcarcinogens can operate For example because many laboratories now use testprotocols aimed at mode of action the 1996 proposed guidelines provide aframework that allows for incorporation of all relevant biological informationand flexibility to consider future scientific advances
In contrast to the single default dose-response relationship (the linearizedmultistage model for extrapolating risk from upper-bound confidence intervals)used in the 1986 cancer guidelines the 1996 guidelines provide several optionsfor constructing the dose-response relationship Biologically basedextrapolation that is extrapolation from animals to humans based on a similarunderlying mechanism of action is the preferred approach for quantifying riskHowever because data for the parameters used in such models are not likely tobe available for most chemicals the 1996 guidelines allow for alternativequantitative methods including several default approaches In the defaultapproaches dose-response assessment is a two-step process In the first stepresponse data are modeled in the range of observation in the second step adetermination is made of the point of departure (benchmark) or the range ofextrapolation below the range of observation In addition to modeling tumordata the new guidelines call for the use and modeling of other kinds ofresponses if they are considered measures of carcinogenic risk Three defaultapproachesmdashlinear nonlinear or bothmdashare provided Curve fitting in theobserved range provides the effective dose corresponding to the lower 95limit on a dose associated with a 10 response (LED10) The LED10 is thenused as a point of departure for extrapolation to the origin as the linear defaultor for an MOE as the nonlinear default The LED10 is the standard point ofdeparture but other departure points can be used when the data justify it
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Other modifications of interest in the 1996 guidelines include the following
bull Emphasis is placed on all biological information rather than only tumorfindings in the hazard-assessment phase of risk assessment
bull Mode of action is emphasized to reduce the uncertainty in describing thelikelihood of harm and in determining the dose-response approaches
bull A weight-of-evidence narrative replaces the current alphanumericclassification categories (A B1 B2 C D E) from the 1986 cancerguidelines The narrative summarizes the key evidence describes theagentrsquos mode of action characterizes the conditions of hazard expressionand recommends appropriate dose-response approaches The overallconclusion on the likelihood of human carcinogenicity is given by routeof exposure Only three descriptors for classifying human carcinogenicpotential are now availablemdashknownlikely cannot be determined and notlikely
bull In contrast to the 1986 guidelines that provide very little guidance for riskcharacterization the 1996 guidelines provide direction on how the overallconclusion and the confidence of risk are presented for the risk managerand call for assumptions and uncertainties to be clearly explained
Time-to-Tumor Models
Because dose-response functions for many chemical substances arederived from lifetime animal-feeding studies results apply to lifetime risk ofcancer The most common dose-response model derived from suchtoxicological experiments describes the lifetime change in cancer incidencewith dose However the stage theory of cancer and other diseases emphasizesthat many harmful exposures can be more accurately characterized as reducingthe time to tumor induction rather than increasing the lifetime risk of tumor(Armitage and Doll 1954) In a time-to-tumor dose-response model importantinformation is disclosed by the time it takes for a fraction of the test subjects toget tumors (Krewski et al 1983) Some animal bioassay data indicate whenindividual bioassay animals died before scheduled terminal sacrifice andwhether they died with or without tumors In some human populations time totumor or other disease is also available Use of time-to-tumor data in theanalysis of the tumor dose-response relationship provides a credible estimate ofthe potency of the carcinogen by incorporating considerable information Thesemodels are not common but have much potential when data are substantial
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Use of Subjective Statistics Bayesian Methods
Bayesian analysis is an important tool now widely used in many domainsincluding some parts of risk analysis (Taylor et al 1993 Evans et al 1994) Itprovides the foundation for the technical field of decision analysis Bayesianapproaches have begun to be applied to assessments of exposure for humanhealth and environmental risks In 2000 Resources for the Future (RFF) inconjunction with EPA and other organizations held a workshop to discuss waysin which Bayesian approaches could be useful in improving techniques forestimating exposure-response functions Participants in the workshop agreedthat wider use of Bayesian approaches can improve human health risk-assessment practices (Wilson 2001) The areas judged to have the mostsignificant opportunities include estimating exposure-response functionsinferring causality especially when interpreting results of epidemiologicalstudies and performing complex exposure assessments
Use of Meta-Analysis in Place of Single-Species Data Sets
In the evaluation of chemical compounds for carcinogenic risk regulatoryagencies have traditionally fit a low-dose linear dose-response model to datafrom rodent bioassays Recently there is much interest in incorporatingadditional scientific information on the properties of the chemical underinvestigation into the risk-assessment process including biological mechanismsof cancer induction However few attempts have been made to investigate theoverall relationship between the shape of dose-response curves and mutagenicity
Assessment of Mixtures
In 1986 EPA issued risk-assessment guidelines for chemical mixtures(EPA 1986b) This framework described three approaches to conduct aquantitative risk assessment for the potential health effects associated withexposure to chemical mixtures First when data are available on the healthimpacts of the mixture of concern or similar mixtures these data should be usedin formulating the risk models When data are not available on the actualmixture or similar mixture of concern data from risk assessments of individualcomponents are then used to estimate the risk of the mixture of concern byapplying a dose-additivity model (second approach) for systemic toxicants and
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a response-additivity model (third approach) for carcinogens Both of thesemodels assume that no interaction occurs among chemicals The two mostaccepted dose-additivity models are the hazard-index (HI) model and thetoxicity-equivalency-factor (TEF) model The response-additivity model is usedprimarily in cancer risk assessment of chemical mixtures it is assumed that thecomponents in the mixture act independently on the same target site but bydifferent mechanisms of action thus the toxicological responses to eachcomponent in the mixture are summed
A significant advance in chemical-mixture risk assessment was the newlydeveloped interaction-based method in which Mumtaz and Durkin (1992) usedbinary interaction data to modify the dose-additive HI Recently EPA (2000a)issued a revised guidance document for chemical mixtures as a supplement tothe original guidelines of 1986 The document Supplementary Guidance forConducting Health Risk Assessments for Chemical Mixtures provides details onthe nature of mixtures and the procedures to use for data analyses It alsodescribes recent scientific advances in the area of chemical-mixture riskassessment including methods for using whole-mixture data on atoxicologically similar mixture methods for incorporating information ontoxicological interactions into an HI (modified from the original methoddeveloped by Mumtaz and Durkin [1992]) procedures for including carcinogeninteractions in mixture risk characterization and generalized procedures forassessing mixtures of similar chemicals
The incompleteness of the classic risk-assessment process as applied tobiosolids can be illustrated by reference to the EPA guidance document (EPA2000a) which details EPArsquos current thinking on the mixture issue A complexmixture is defined as ldquoa mixture containing so many components that anyestimation of its toxicity based on its componentsrsquo toxicities contains too muchuncertainty and error to be useful The chemical composition may vary overtime or with different conditions under which the mixture is produced Complexmixture components may be generated simultaneously as by-products from asingle source or process intentionally produced as a commercial product ormay coexist because of disposal practices Risk assessments of complexmixtures are preferably based on toxicity and exposure data on the complexmixturerdquo (EPA 2000a) Chapter 3 shows that health risk data on the completemixture are insufficient in the case of biosolids to provide the basis for a riskassessment Hence assessors are dependent on a component-based assessmentstrategy that while not containing ldquotoo much uncertainty and error to beusefulrdquo will be incomplete as a basis for defining a strictly prospective strategyfor risk management (EPA 2000a)
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Advances in the Exposure Characterization Process
There have been a number of important changes in the exposurecharacterization process over the past decade Among the changes of note areincreasing focus on indoor and residential environments methods formonitoring biological agents in exposure media (air water and soil) amovement away from simple bounding estimates to probabilistic assessmentsthat include explicit treatment of uncertainty and variability and the use ofmultimedia and multiple-pathway exposure assessments In the sections belowthe committee highlights the changes in exposure assessment methods that haveparticular relevance to biosolids risk assessments A review and evaluation ofspecific exposure pathways in the Part 503 rule risk assessment are provided inChapter 5
Ten years ago it was common to conduct an exposure assessment usingsimple models that define a maximum exposed individual (MEI) The MEI wasone who obtained all of his or her air water andor food from an areacontaminated by the pollutant of interest over a lifetime The implicit andunquantified overestimate of exposure in the MEI as well as the failure of theMEI to capture all exposure pathways led to a search for alternative schemesAt first there was an effort to define a highly exposed individual (HEI) assomeone who had a plausibly high exposure but less exposure than the MEIHowever the HEI was found to have many of the same limitations as the MEICurrent practice is to use a reasonable maximum exposure (RME) receptorEPA (1989) specifies that calculation of the RME requires a combination ofaverage and upper-bound values for various exposure parameters so that thefinal exposure estimate will represent an upper bound exposure that couldreasonably be expected to occur This is commonly interpreted to be a 90th to95th percentile of exposures for each pathway Due to its inconsistentcombination of upper percentile and mean values the RME approach can bearbitrary and fail to fully account for population exposure variabilityNevertheless the use of RME in place of HEI has fostered the increasing use ofprobabilistic methods in exposure assessments (EPA 2001b) In its recentassessment of exposures to dioxins in biosolids EPA partially makes use of aprobabilistic risk-assessment approach (EPA 2001c)
Increased Focus on Indoor and Residential Environments
One theme that is clear in the literature on exposure assessment is theimportance of the indoor environment and residential factors in understand
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ing human exposure to many agents Indoor and residential scenarios receivedlittle attention in the Part 503 rule risk assessment but those issues havereceived much greater attention in risk-assessment practice over the last decade
Assessments of the human health impact of airborne pollutants revealedthe importance of cumulative exposure to microenvironments such as indoorair and of household sources such as consumer products combustionappliances and tracked-in soil Efforts to better understand urban air pollutantssuch as particulate matter revealed the importance of increased indoorconcentrations of certain pollutants (Melia et al 1978 Dockery and Spengler1981 Spengler et al 1983) Subsequent studies most notably EPArsquos TotalExposure Assessment Methodology (TEAM) studies demonstrated that for avariety of contaminants residential indoor air is often a more significant sourceof exposure than outdoor air (Pellizzari et al 1986 Thomas et al 1993 Wallace1993)
Methods for Monitoring Biological Agents in Exposure Media
Although the issue of exposure to and risk from pathogens is addressed inChapter 6 it is of note here that methods available for monitoring exposure topathogens have improved greatly in the last decade Traditional detection ofmicroorganisms is performed using microscopy culture biochemistry orimmunoassay Microscopy is used to detect total microbial populations in agiven sample without regard to the physiological state of the organism bothviable and nonviable organisms can be detected Culture-based assay is limitedto detection of those organisms that will proliferate under the growth conditionsof the analysis design Biochemical and immunological-based analyses haveimproved the identification and enumeration of specific microbial contaminantsin environmental samples Improved detection and identification ofmicroorganisms have been achieved using advanced biotechnology-basedmethodologies including polymerase chain reaction (PCR) amplificationmicrochips molecular beacons electrochemiluminescence biosensors massspectrometry and flow cytometry
Explicit Treatment of Uncertainty and Variability
Estimating potential human exposures and source-to-dose relationships forharmful substances in biosolids involves the use of models and large amounts ofdata Because these data and models must be used to predict individualbehaviors engineered system performance contaminant transport humancontact and uptake and dose among large and often heterogeneous
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populations variability and uncertainty associated with these predictions arelarge
Over the last decade explicit assessment of sensitivity and uncertainty hasbecome common practice in many risk assessments This practice has beendriven in large part by the ready availability of software for uncertainty andsensitivity analysis improvements in computers that make it possible to runlarge numbers of repeated simulations and the availability of Monte Carloguidance from EPA (1997b) Also supporting this process is the wideravailability of summary statistics for exposure factors available in referencessuch as the EPA (1997a) Exposure Factors Handbook
One of the key issues in uncertainty analysis that has been addressed overthe last decade is how to distinguish between the relative contribution of trueuncertainty and that of interindividual variability (heterogeneity) to characterizethe predicted population risk (Bogen and Spear 1987 NRC 1994) Uncertaintyor model-specification error (eg statistical estimation error) can be modeledusing a random variable but the characteristics of this variable are oftensubjective In contrast variability refers to quantities that are distributedempirically within a defined population Such factors as food ingestion ratesexposure duration and expected lifetime are considered as variable but notuncertain The recognition of the difference between uncertainty and variabilityhas resulted in efforts to carry out assessments in which both uncertainty andvariability are characterized in the final results
The Habicht memo (1992) seems to have encouraged the growth in effortsto address uncertainty The recent Exposure Factors Handbook (EPA 1997a)the Monte Carlo guidance document (EPA 1997b) and the recent report onpolicy for use of probabilistic risk assessment (EPA 1997c) reveal that EPA hasand will continue to support and encourage more explicit treatment ofuncertainty and variability In its 1997 Monte Carlo guidelines and itsSuperfund guidance for conducting probabilistic risk assessment EPAidentified a tiered scheme for updating and calibrating a model as more databecome available (EPA 1997b 2001b) As a first step in this scheme thevariance of all input values should be clearly stated and the impact of thesevariances on the final estimates of risk should be assessed using sensitivityanalysis Here it helps to provide a clear summary and justification of theassumptions used for each aspect of a model In addition it should be statedwhether these assumptions are likely to result in representative values orconservative (upper bound) estimates The next step in this scheme is the use ofvariance propagation methods (including but not necessarily limited to MonteCarlo methods) to map how the overall precision of risk estimates is tied to thevariability and uncertainty associated with model choice inputs and scenarios
The risk assessment for the Part 503 rule does not provide a clear analysisof uncertainties and their potential impacts on the assessment of risks A
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quantitative analysis would allow identification of critical parameters that havea strong influence on the outcome of the calculations of risk However thelimits of time and resources at EPA mean that choices must be made whenplanning whether and how to update risk assessments and collect site-specificdata in support of the risk assessment calculations In making revisions to thebiosolids risk assessment EPA must strike a balance between expendingresources to carry out site-specific data collection and expending resources tomodel and assess risk using existing information
Multimedia and Multiple-Pathway Exposure Assessments
Efforts to assess human exposure to contaminants from multipleenvironmental media have been evolving over the past several decadesKnowledge of potential environmental pathways is an important component ofa health risk assessment for biosolids The need to assess human exposure toglobal fallout in the 1950s resulted in the development of a framework thatincluded transport of contaminants through air soil surface water vegetationand food chains More recently reported concentrations of semivolatile organiccompounds and mercury species in water vegetation soil and food productshave increased interest in more accurate characterizations of chemical transporton a local regional and global scale In response to the need for bettercharacterization a number of multimedia transport and transformation modelsfor organic chemicals and metal species have appeared Multimedia models arealso being developed for pathogens Over the past decade or so relativelydetailed single-domain transport and transformation models have beendeveloped to model aspects of chemical transport and transformation within asingle medium or domain (eg groundwater models vadose zone modelssurface-water mixing models and air-dispersion and transformation models)
Multimedia multipathway assessments have fostered increasing interestabout indirect exposure pathways But only limited efforts have been made todevelop source-to-dose relationships using multimedia models Moreover thesecomplex source-to-dose models are difficult to validate The increasingsophistication of mass-transfer models has as yet had almost no impact onhuman exposure models None of the exposure models available to dateprovides an integrated simulation of major transport processes and indoor andoutdoor relationships for toxic substances in air water food and soil
The Food Quality Protection Act (FQPA) of 1996 draws attention to theneed for methods to assess aggregate intake of agents with similar target organs
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Biological Markers
Outside of occupational settings or specific research studies most currentexposure-sampling strategies do not rely on biological markers Although thereare reasonable biomarker methods for several metals (eg mercury arseniccadmium chromium) and some organic compounds the lack of reliable andnonintrusive biomarkers continues to limit their widespread use in exposuretracking studies For example the Centers for Disease Control and Prevention(CDC) is exploring biomarkers for classes of organophosphate (OP) pesticidesIn some occupational settings biological markers (eg for lead) are part of thesurveillance process It is feasible that a set of biomarkers could be createdusing less invasive methods (eg urine saliva and hair sampling) Urinarybiomarkers have worked well for some metals tobacco smoke and some otherpollutants As new biomarkers are developed and existing ones improvedemerging sampling strategies will rely more on them It is conceivable that inthe future EPA will be able to evaluate more DNA adducts possibly even afterexposure of embedded personal DNA worn by individuals as a monitor Formany contaminants of concern in biosolids biomarker approaches may be bothfeasible and informative However for the near future it is not likely thatbiomarkers will be of great value for monitoring exposures near biosolids-application sites
Challenges to the Risk-Characterization Process for Biosolids
The emphasis here is on how the process of risk characterization ischanging and how those changes impact the Part 503 rule Particular challengesto the risk-characterization process are to better link risk assessment to riskmanagement consider risk perception and risk valuation more explicitly andprovide better risk communication between risk assessors and affectedpopulations
To examine the Part 503 rule risk assessment in the context of the evolvingrisk-assessment paradigm EPA must consider the objectives of the Part 503rule risk assessment Was it to convince the community that it is safe Was it tojustify what is being done or what has been decided Was it to organizeinformation on exposures and health effects to communicate what is known andwhat the information gaps and key uncertainties are
One key risk characterization and management issue that emerged duringthe committee discussions was whether quality-of-life issues that have thepotential to affect health such as odors should be considered a factor in
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setting standards for land application of biosolids In particular couldminimizing odors be an effective way to manage some potential risks
Acceptance of a risk assessment by regulators and community groups oftenrequires surveillance and monitoring to ensure that the assumptions used in therisk assessment are in place Many of the chemical substances in municipalwaste streams are also in biosolids The chemicals in municipal solid-wastelandfills are monitored Should the same chemicals be monitored followingbiosolids application Answers to these questions help to put the riskassessment in both a scientific and political context That is once the objectivesof the risk assessment are established what and whose decisions are beinginformed by the assessment and the level of scientific confidence needed can beidentified
Characterizing Exposures to Children as a Subpopulation
Organizations such as EPA and the National Institutes for Health aregiving special consideration to childrenrsquos risks from exposure to environmentalcontaminants In 1996 EPArsquos Office of the Administrator issuedEnvironmental Health Threats to Children (EPA 1996c) and set an agenda thatcalled for consideration of childrenrsquos risks in all EPA actions The report alsoemphasized the need for more research to support childrenrsquos risk assessmentsChildren are considered a special subpopulation because their health risks candiffer from those of adults because of their immature physiology metabolismand differing levels of exposure due to factors such as greater food consumptionper unit of body weight and outdoor play activities
Differing levels of exposure for children are typically considered in riskassessments but the underlying toxicity database often does not specificallyaddress effects on children Such limitations in toxicity data are typicallyaddressed by application of uncertainty factors to protect susceptiblepopulations such as children Additional research would allow an assessment ofthe adequacy of such uncertainty factors
Participation of the Affected Populations
Local opposition to land application of biosolids appears to be growing inpart because regulators such as EPA have failed to systematically addressconcerns and experiences of residents near land-application sites Because noprocess is in place to register complaints EPA might be unaware of complaintslodged with a local or state agency Public meetings held by the com
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mittee have identified residents near land-application sites and biosolidsappliers who believe that they have suffered health impacts and believe thatthey have been excluded from having input in the risk-assessment processHealth complaints include irritation of the eyes nose and throat headachesnausea cough chest tightness congestion shortness of breath drowsinessskin lesions and mood disorders (Schiffman et al 2000 Shields1) Thecommittee was not charged with the task of evaluating the legitimacy of thecomplaints nor of determining whether application of sewage biosolids isrelated to the complaints However it notes that the primary concerns ofneighbors to land-application sites and the alleged health impacts associatedwith land application of biosolids have not been addressed in the riskassessments upon which the Part 503 rule is based
A critical aspect of the risk-assessment process is ensuring that thoseassessing risks are asking the right questions Potentially affected people oftenhave knowledge to contribute to the accurate characterization of exposures andto the assessment of risks When such knowledge is not tapped the outcome ofthe process can be flawed rejected by stakeholders or both Tapping localknowledge is necessary but not sufficient to characterize risks Some risks suchas secondary exposures or effects with long periods of latency might not beapparent to those exposed
The risk assessment in support of the Part 503 rule was the product ofagency and academic experts including individuals with long-term associationswith land applications and awareness of community concerns As requiredunder federal law EPA took public comment on the proposed regulationsNevertheless there was no evidence of efforts to engage people living adjacentto sites where biosolids are being or could be applied at the level recommendedby the PresidentialCongressional Commission on Risk Assessment and RiskManagement (1997) EPA guidance such as the supplement to Risk AssessmentGuidance for Superfund Part A (EPA 1999a) provides information to improvecommunity involvement in the Superfund risk-assessment process Specificallythis document identifies where community input can augment and improveEPArsquos estimates of exposure and risk and illustrates why communityinvolvement is valuable during the human health risk-assessment process
1HShields Citizens for a Future New Hampshire and the New Hampshire SierraClub Sludge Victims May 2001 Update Materials provided to the committee on June 42001
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Link Between Risk Assessment and Management of Land-Application Sites
Risk assessments are conducted with the assumption that specificmanagement practices are in place and remain in force If these practices are notfollowed the estimated risks can differ from those estimated under the assumedmanagement practices The risk assessment for the Part 503 rule was conductedwith the assumption that specific management practices are followed Forexample complete incorporation of biosolids into the soil is assumed inassessing runoff impacts For many sites however surface application topastures is normal practice and is allowed under the Part 503 rule Surfaceapplication provides the potential for erosion and off-site movement ofbiosolids and their constituents in a form much different from that assumed inthe risk assessment
The risk assessment for the Part 503 rule included the assumption thatspecific management practices are followed However because the rule doesnot explicitly require some of these practices it is difficult to confirm the extentto which site operators employ these management practices Some are measuresthat may be useful in minimizing risks however most are not requirementsunder the Part 503 rule
It should be recognized that even in cases in which specific managementpractices are clearly delineated and required under regulations there can becases in which management practices are not followed through oversightnegligence or willful noncompliance Efforts to make risk assessment morerealistic are challenged by the issue of dealing with the likelihood ofnoncompliance For example risks of home-use pesticides are assessedassuming that label directions are followed yet experience shows that asignificant number of users disregard such directions In the case of landapplication of biosolids concerns have been raised about the ability of EPA toenforce the Part 503 rule (EPA 2000b) When there are such alleged violationsas applying biosolids within buffer zones and grazing of livestock on land lessthan 30 days after Class B biosolids were applied any risk assessment thatignores the likelihood of those violations will not be applicable where thoseconditions exist No information is available on the frequency and severity ofviolations of management requirements Moreover the committee is not awareof any risk assessment that was carried out under the assumption that one ormore violations had occurred An assessment of the risks both with and withoutthe specified management practices would indicate the significance ofnoncompliance This would provide information to be used in risk-managementdecision-making Without a system that provides for registration investigationenforcement and documentation of complaints concerning management
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practices EPA will not be able to compile relevant data on the level ofcompliance with biosolids management requirements in the Part 503 rule
Odors present a challenge to risk assessors and managers Until recentlyodors were assumed to be an aesthetic issue Odor control however is animportant focus of recommendations for good practice (NBP 2001) andSchiffman et al (2000) have suggested that odors can affect health Odors anddisease vectors as health issues are clearly within the scope of EPA Less clearis whether EPA may address quality-of-life issues such as enjoyment ofproperty where odors or flies might be objectionable but not an unacceptablehealth risk
CHANGES IN RISK-ASSESSMENT APPROACHES IN EPAOFFICES
A number of EPA offices and programs are involved in developing risk-assessment protocols for chemical releases to ambient air indoor air surfacewater soil and groundwater The methods developed in these programs and theevolution of risk-assessment methods within these offices and programs overthe past 10 years provide benchmarks against which the relevance andreliability of the Part 503 rule risk assessments can be evaluated The committeerecognizes that other government agencies such as the CDC the USDepartment of Agriculture and the National Institute of Environmental HealthSciences have also been involved in research of risk-assessment methods andin developing risk-assessment protocols In some cases those agencies have hada direct interest in biosolids risk Nevertheless the committee believes that it isbeyond the scope of this report to explore the evolution of the risk-assessmentprocess in all US government agencies Moreover because EPA has leadresponsibility for biosolids risk and works closely with other agencies on issuesof risk assessment the committee decided to focus on the offices of EPA in itsreview of risk-assessment methods in the US government
Office of Research and Development (ORD)
EPArsquos ORD is the principal scientific and research arm of EPA Itconducts research and fosters the use of science and technology in fulfillingEPArsquos mission ORDrsquos two major programs involved in developing guidanceon risk assessment are the National Center for Environmental Assessment andthe National Exposure Research Laboratory A brief description of some
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of the major risk-assessment developments in each of these programs isprovided below
National Center for Environmental Assessment (NCEA)
NCEA serves as the national resource center for the overall process ofhuman health and ecological risk assessments It develops methods that reduceuncertainties in risk assessments (eg dose-response models and exposuremodels) conducts assessment of contaminants and sites of nationalsignificance and provides guidance and support to risk assessors Two majorprogram areas with important developments since the risk assessments wereconducted for the Part 503 rule are exposure assessment and cancer assessment
Exposure Assessment
In 1992 EPA promulgated a new set of exposure-assessment guidelines toreplace the 1986 version (EPA 1992a) The new guidelines explicitly considerthe need to estimate the distribution of exposures among individuals andpopulations and discuss the need to incorporate uncertainty and variabilityanalysis into exposure assessments The guidelines discuss the roles of bothanalytic measurement and mathematical modeling in estimating concentrationsand durations of exposure They do not recommend specific models but suggestthat models match the objectives of the particular exposure assessment beingconducted and that they have the accuracy needed to achieve those objectivesThey also call for detailed explication of the choices and assumptions that oftenmust be made when faced with incomplete data and insufficient resources
In 1997 NCEA published a support document to the guidelines called theExposure Factors Handbook (EPA 1997a) It contains a summary of humanbehaviors and characteristics that affect exposure to environmentalcontaminants and recommends values to use for these factors A new exposurefactors handbook dealing specifically with children is in development EPAgives special consideration to children because they can be more heavilyexposed to environmental contaminants than adults EPA released an externalreview draft of the handbook in June 2000 (EPA 2000c)
NCEA has also developed a guidance document on how to conduct dermalexposure assessments (EPA 1992b) The dermal route of exposure is notunderstood as well as the other major routes of exposure (ingestion andinhalation) NCEArsquos guidelines discuss the principles of dermal absorption
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from exposures to water soil and vapor media and presents methods forapplying those principles to human exposure assessment The guidelines weredeveloped primarily for evaluations of waste-disposal sites or contaminatedsoils but are applicable to land-applied biosolids The Office of Solid Waste andEmergency Response has also developed guidance for dermal risk assessment(EPA 2001a)
Guidance is also being developed for approaches to modeling health risksfrom indirect exposures to environmental contaminants For exampleMethodology for Assessing Health Risks Associated with Multiple Pathways ofExposure to Combustor Emissions (EPA 1998b) presents procedures forestimating exposures resulting from atmospheric pollutants emitted fromstationary combustors transferred through the atmosphere and deposited onenvironmental media and biota It discusses ways to estimate indirect exposuresthat could result from uptake and transfer from atmospheric agents through theterrestrial or aquatic food chains This example also illustrates the need forconducting multimedia and multiple-pathway exposure assessments
Cancer Risk Assessment
In 1996 NCEA proposed a revision to the 1986 EPA Guidelines forCarcinogen Risk Assessment to reflect new developments in understandingcarcinogenesis (EPA 1996a) Revisions have been made since that proposaland work on the guidelines is still in progress (EPA 1999b) The proposedrevisions include placing greater emphasis on analyzing all the biologicalinformation on an agent rather than analyzing only the tumor dataunderstanding an agentrsquos mode of action taking a weight-of-evidence approachto drawing conclusions about hazard and providing guidance on assessing risksto children When finalized the guidelines will provide an analytical frameworkthat will allow the incorporation of all relevant biological informationrecognize a variety of situations regarding cancer hazard and be flexibleenough to allow consideration of future scientific advances
National Exposure Research Laboratory (NERL)
NERL is EPArsquos resource for guidance on exposure assessment for allenvironmental stressors (eg chemicals biological agents and radiation)NERL conducts research on stressor sources pollutant transporttransformation and exposure and source-to-receptor predictive exposuremodels NERL is also involved in the development of innovative exposure-assessment technologies
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National Exposure Surveys
One of NERLrsquos major efforts is to address the need to reduce uncertaintyand variability in exposure assessments and the need to develop realisticexposure scenarios and assumptions A key determinant of exposure variabilityis human activity Between October 1992 and September 1994 NERLconducted the National Human Activity Pattern Survey (NHAPS) to collectdata on activity patterns of subjects over a 24-hour period The survey wasintended to provide comprehensive exposure information over broadgeographical and temporal scales that can be used for detailed exposure studiestargeted to specific populations in the United States Detailed tables of thesurvey results have been compiled (EPA 1996d) and some of the data wereincorporated into the Exposure Factors Handbook (EPA 1997a)
NHAPS provides a broad description of individual activities for distinctcombinations of location and time (macroactivity [eg amount of time spent inan enclosed vehicle]) For specific risk assessments activity patterns can beanalyzed in even greater detail using microactivity models which can be usedto describe specific contacts with exposure media (eg frequency of a childrsquoshand contact with soil and mouth) Exposures from residential environmentshave been given greater attention in recent years
Another survey that was undertaken is the National Human ExposureAssessment Survey (NHEXAS) This survey was designed to evaluatecomprehensive human exposure to multiple chemicals on a community andregional scale The first phase of the survey involved measuring concentrationsof chemicals in various exposure media (eg air food drinking water soil anddust) and in biological samples (eg blood and urine) and administeringquestionnaires to identify possible sources of exposure to chemicals Thesample collection and laboratory analyses were completed in 1998 andstatistical analyses of the data are being performed As the database isdeveloped it will be possible to use the data as a baseline to determine whetherspecific populations are exposed to increased levels of environmentalcontaminants
Pharmacokinetic Models and Biomarker Data
NERLrsquos Exposure Methods and Monitoring Branch develops indicators ofhuman exposure to environmental stressors One set of indicators that providesa direct measure of exposure is biomarker data sets Biomarkers are indicatorsspecific to a contaminant of variation in cellular or biochemical components orprocesses structure or function that are measurable in biological systems orsamples When used with pharmacokinetic data and informa
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tion on the interval between exposure and collection of the biomarkerinformation biomarker data can be used to reduce uncertainties about exposure
The study of pharmacokinetics provides an understanding of a chemicalrsquosabsorption distribution metabolism and excretion that occurs between the timea chemical enters the body and when it leaves Pharmacokinetic models are amathematical representation of those processes and can be used to describe thequantitative differences between an exposure dose a delivered dose and whenpossible a biologically active dose at the target organ EPArsquos strategic plan forevaluating data from NHEXAS (EPA 2000d) discusses the need to considerpharmacokinetic models and parameters in evaluating the time course andassociations between exposure and dose
Office of Air and Radiation (OAR)
EPArsquos OAR is responsible for national programs technical policies andregulations for controlling air pollution and radiation exposure Currently thereare OAR programs to address pollution prevention indoor and outdoor airquality industrial air pollution pollution from vehicles and engines radon acidrain stratospheric ozone depletion and radiation protection Of particularinterest for considering applications of risk-assessment policy are the RadiationProtection Division Indoor Air Quality Programs and the Office of Air QualityPlanning and Standards within OAR
Radiation Protection Division
The Radiation Protection Programs within the Radiation ProtectionDivision provide the methods and scientific basis for EPArsquos radiation exposuredose and risk assessments These assessments in turn support the developmentof EPA policy guidance and rule-makings concerning radiation protection andrisk management Among other functions the Radiation Protection Programdevelops radionuclide fate and transport models dose and risk models and doseand risk coefficients
Indoor Air-Quality Programs
Because of the importance of understanding the sources and pathways ofexposure in indoor environments EPA has established and promoted indoor air-quality programs over the past decade These programs deal with indoor
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exposures to contaminants originating from both outdoor and indoor sourcesAmong the sources of indoor pollution addressed by EPA are combustionsources such as oil gas kerosene coal and wood-combustion and tobaccoproducts building materials and furnishings such as wet or damp carpet andcabinetry or furniture made of certain pressed-wood products householdcleaning and maintenance products central heating and cooling systems andhumidification devices and outdoor sources such as radon pesticides andoutdoor air pollution Of particular interest to the issue of biosolids riskassessment is the potential for indoor exposures to pathogens
Office of Air Quality Planning and Standards (OAQPS)
EPArsquos OAQPS directs national efforts to meet air-quality goalsparticularly for smog air toxics carbon monoxide lead particulate matter (sootand dust) sulfur dioxide and nitrogen dioxide OAQPS is responsible forimplementing major provisions of the Clean Air Act including those related tovisibility permitting and emissions standards for a wide variety of industrialfacilities Of particular interest in risk assessment is the OAQPS effort todevelop methods to assess human exposure and health risks for particulatematter (PM) and multimedia pollutants released in urban air sheds As part ofthat effort OAQPS has formulated advanced and novel methods for addressingmultimedia pollutants Those methods are being incorporated into the OAQPStotal risk integrated model (TRIM) TRIM provides a multimedia fate analysisand multipathway exposure assessment for toxic air pollutants and aerosols(PM)
OAQPS is also working on the National Air Toxics Assessment (NATA)a program to assess the cumulative exposures of the US population to toxic airpollutants through a combination of monitoring and models
The OAQPS effort to assess PM exposure has particular relevance tobiosolids risk PM exposure from biosolids application is raised as a concern oflocal communities and some public-health officials From biosolids-applicationsites PM is produced by numerous sources including diesel emissions trafficand dust suspensions A related issue is raftingmdashpathogens catching a ride ondust particles Whether and how allergen proteins are transported from site toreceptor is still poorly understood
Office of Solid Waste and Emergency Response (OSWER)
OSWER provides policy guidance and direction for EPArsquos solid-wasteand emergency-response programs Within OSWER the Office of Solid
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Waste (OSW) develops guidelines for the land disposal of municipal andhazardous waste and the Office of Underground Storage Tanks (OUST)develops guidance for limiting the risks from leaks of underground storagetanks OSWER provides technical assistance to all levels of government toestablish safe practices in waste management OSWER is also home to theSuperfund program which addresses health concerns of communities withabandoned and active hazardous waste sites and accidental oil and chemicalreleases Superfund also encourages innovative technologies to addresscontaminated soil and groundwater
Office of Solid Waste (OSW)
OSW is responsible for setting limits on the concentrations of chemicalsthat can be placed in municipal landfills Limits are set through a risk-assessment process that identifies and evaluates multiple exposure pathwaysOSW has identified a number of potential exposure pathways linked to landfillsand uses multimedia risk assessments to link human exposure and health risk tochemicals in the landfill waste The assessment is a forward-calculating analysisthat evaluates the risks of multiple exposure pathways to human and ecologicalreceptors One of the pathways that the OSW landfill risk assessments addressesis the advection of chemicals out of the landfill due to forced convection thatresults from methane and carbon dioxide generation in the waste pile
Office of Underground Storage Tanks (OUST)
OUST was created in 1985 to carry out a congressional mandate todevelop and implement a regulatory program for underground storage tank(UST) systems OUST works with EPA regional offices and state and localUST programs to promote the use of risk-based decision-making In OUSTrisk-based decision-making (RBDM) is a process by which decisions are madeabout contaminated sites using a site-specific assessment of the risk each siteposes to human health and the environment In cooperation with the AmericanSociety for Testing and Materials (ASTM) OUST is evaluating whether itsRBDM programs are achieving their stated agency management goals
Office of Emergency and Remedial Response (OERR)
The EPA Superfund program is administered by the OERR After a
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hazardous waste site is listed on the National Priorities List risk assessment hasan important role in the characterization and cleanup of Superfund sites OERRprovides general tools and specific tools to assist in the major steps of the risk-assessment process In 1989 Risk Assessment Guidance for Superfund (RAGS)Part A was issued (EPA 1989) This document provides recommendedalgorithms and data for calculating potential exposures to chemicalcontaminants found at Superfund sites In contrast to the OUST risk methodsRAGS are more generic in providing uniform national risk-assessment defaultsAdditional RAGS documents were issued in 1991 in Part B (EPA 1991b)which provides guidance on using EPA toxicity values and exposureinformation to derive risk-based preliminary remediation goals and Part C(EPA 1991c) which provides guidance on the human health risk evaluations ofremedial alternatives In 1998 OERR issued Part D (EPA 1998c) and in 1999it issued a supplement to Part A (EPA 1999a) This document is of interest tobiosolids risk assessors because the supplement provides information toimprove community involvement in the Superfund risk-assessment processSpecifically the supplement suggests ways for Superfund staff and communitymembers to work together during the early stages of Superfund cleanupidentifies where community input can augment and improve EPArsquos estimates ofexposure and risk recommends questions that the site team should ask thecommunity and illustrates why community involvement is valuable during thehuman health risk assessment at Superfund sites A review draft of Part Eprovides dermal risk assessment guidance (EPA 2001a) OERR has alsodeveloped probabilistic risk assessment guidance for Superfund (EPA 2001b)
Office of Water (OW)
EPArsquos OW is responsible for all national water-quality activities includingthe regulation of surface water and groundwater supplies to protect humanhealth and the environment OW is responsible for implementing the CleanWater Act Safe Drinking Water Act and portions of other environmental lawsand treaties that apply to water quality Several organizations make up the OWincluding the Office of Wetlands Oceans and Watersheds the Office ofScience and Technology the Office of Wastewater Management (whichoversees EPArsquos biosolids program) and the Office of Ground Water andDrinking Water
A major task of OW is to set drinking-water standards Risk assessmentprovides a key input to this process Since 1986 OW has more than tripled thenumber of contaminants for which it has published drinking-water stan
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dards bringing the total to 94 A current challenge for OW in its effort tominimize health risks from water supplies is to find the appropriate balancebetween the risks from naturally occurring microbial pathogens and thechemical by-products of disinfection processes used to remove the pathogens Itis important to provide protection from these microbial pathogens whileensuring decreasing health risks to the population from disinfection by-products
As part of its effort to protect watersheds OW has established the totalmaximum daily load (TMDL) program A TMDL is a calculation of themaximum amount of a pollutant that a body of water can receive and still meetstate water-quality requirements TMDLs are determined in part by consideringmultiple sources of pollutants (from point nonpoint and background sourcesincluding atmospheric deposition) seasonal variations and margins of safetyThe calculations of these programs provide benchmarks for the continuingevaluation of biosolids standards
Office of Prevention Pesticides and Toxic Substances(OPPTS)
EPArsquos OPPTS develops national strategies for toxic substance control andpromotes pollution prevention and the publicrsquos right to know about chemicalrisks OPPTS has an important role in protecting public health and theenvironment from potential risk from toxic chemicals and pesticides OPPTS isdealing with issues such as endocrine disruptors and lead poisoning prevention
Within OPPTS the Office of Pesticide Programs (OPP) regulates the useof all pesticides in the United States and establishes maximum concentrationsfor pesticide residues in food As part of this effort OPP is expanding access toinformation on risk-assessment and risk-management actions to help to increasetransparency of decision-making and facilitate consultation with the public andaffected stakeholders OPP has a mandate under the FQPA of 1996 to addressaggregate exposure and cumulative risk from multiple sources of pesticideexposure To address that issue OPP developed a framework for conductingcumulative risk assessments for organophosphates and other pesticides thathave a common mechanism of toxicity (that act in the same way in the body)Through its cumulative risk-assessment framework OPP will be able toconsider whether the risks posed by a group of pesticides that act the same wayin the body meet the FQPA safety standard of ldquoreasonable certainty of noharmrdquo As part of that framework OPP is developing new methods to assesscumulative risk to assess residential exposure and to aggregate exposures fromall nonoccupational sources
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FINDINGS AND RECOMMENDATIONS
The Part 503 rule risk assessments were carried out more than a decadeago In this chapter the committee considered the likely impact of changes inrisk-assessment practice in general and in various EPA offices in particular onthe risk-assessment process for biosolids The committee found that thedevelopment of methods in the broader academic community and the evolutionof risk-assessment methods within various EPA offices and programs provideimportant benchmarks for the committeersquos assessment of the relevance andreliability of the Part 503 rule risk assessments Of particular note are updates tothe risk-assessment framework recommended by the NRC the PresidentialCongressional Commission on Risk Assessment and various EPA offices
The risk-assessment methods and policies practiced and advocated at EPAhave changed significantly although not at the pace recommended by the NRCand the risk commission As a result the Part 503 rule which has not beenmodified to account for any new methods and policies is now inconsistent withcurrent NRC recommendations and EPA policies within various officesParticularly relevant examples of the inconsistency are the absence ofstakeholder participation and the lack of explicit treatment of uncertainty andvariability
Recommendation Because of the significant changes in risk-assessmentmethods and policies over the last decade EPA should revise and update thePart 503 rule risk assessments Important developments include recognition ofthe need to include stakeholders throughout the risk-assessment processimprovements in measuring and predicting adverse health effects advances inmeasuring and predicting exposure explicit treatment of uncertainty andvariability and improvements in describing and communicating risk EPA should consider how the updated risk assessments would change the risk-management process A similar approach can be taken with the issue ofbiological agent risks
In recent years health-effects research has made use of large-scale studiesof human health end points at multiple sites Health-effects research has alsofocused on early indicators of outcome making it possible to shorten the timebetween the exposure and the observation of an effect In addition more use hasbeen made of meta-analysis better modeling of dose-response relationshipsand more sophisticated regression models These improvements make possiblemore site-specific assessments of the impacts of biosolids land-applicationpractices
Managing exposure of human populations to environmental contaminantsusing a risk-based approach requires an accurate metric for the impacts of
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contaminants on human health and a reliable process for monitoring andrecording the exposures within populations assumed to be at risk Over the pastdecade the practitioners of exposure assessment have made importantimprovements in methods to measure and model source-to-dose relationshipsThese improvements have been made through greater use of time-activitysurveys personal monitors and biomarkers of exposure and they have made itpossible to confirm some of the exposures predicted in risk assessments
Recommendation Many of the measures of risk used in developing thePart 503 rule guidelines cannot be monitored Because of that inability tomonitor the committee acknowledges that EPA must perform theoretical riskassessments Nevertheless there is a continuing need to provide some measuresof performance that can be monitored (eg concentrations of selectedchemicals in exposure media such as indoor air house dust or tap water ofresidences near land-application sites and exposure biomarkers in the blood or urine of nearby residents) Recent improvements in health surveillance andexposure monitoring provide new opportunities for EPA to develop moreexplicit and measurable metrics of performance for biosolids land-applicationpractices
Advancements in monitoring health outcomes and exposure have resultedin improvements in the description and communication of risk In particularimproved exposure assessments have led to better exposure classification inhealth-effects studies Better descriptions of risk are available using benchmarkdose and margin of exposure to communicate hazard and risk in place of risk ofdeath hazard quotients or exposure-potency product relationships There havealso been improved methods for prioritizing compounds using measures of risk
Recommendation In making revisions to the Part 503 rule riskassessment EPA must strike a balance between expending resources to carryout site-specific data collection and expending resources to model and assessrisk using existing information In light of improvements in exposure and healthmonitoring the committee encourages EPA to consider options carefully forcollecting new data in support of risk-assessment assumptions before resortingto another risk assessment that relies only on existing data models and defaultassumptions Among the data that would be of value are data on proximity of receptors to land-application sites surveys of activities that could increasedirect and indirect exposures and samples of biosolids air vegetation runoffgroundwater and soil in environments surrounding land-application sites Inaddition EPA should conduct site-specific surveys of performance (egmonitor the extent to which rates and depth of application are consistent withrisk-assessment assumptions) and scientifically relevant studies of health complaints
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Risk assessments make use of a number of assumptions to define chemicalloading in biosolids that pose no undue risk to surrounding populations Implicitin this process is the premise that these assumptions and the associateddemographic and operational conditions will persist However there are noguidelines to ensure that these conditions persist
Recommendation Because there are no guidelines to ensure thatconditions assumed in the risk assessment actually transpire the committeerecommends that the Part 503 rule provide guidance for periodic reassessmentsthat will be used to ensure that the demographic and operational conditions ofbiosolids land application are consistent with the assumptions of the applicablerisk assessment
REFERENCES
Armitage P and RDoll 1954 The age distribution of cancer and a multistage theory ofcarcinogenesis Br J Cancer 8(March)1ndash12
Barnes DG GPDaston JSEvans AMJarabek RJKavlock CAKimmel CPark andHLSpitzer 1995 Benchmark Dose Workshop Criteria for use of a benchmark dose toestimate a reference dose Regul Toxicol Pharmacol 21(2)296ndash306
Bogen KT and RCSpear 1987 Integrating uncertainty and interindividual variability inenvironmental risk assessment Risk Anal 7(4)427ndash436
Dockery DW and JDSpengler 1981 Indoor-outdoor relationships of respirable sulfates andparticles Atmos Environ 15(3)335ndash343
EPA (US Environmental Protection Agency) 1986a The Risk Assessment Guidelines of 1986EPA6008ndash87045 Office of Health and Environmental Assessment US EnvironmentalProtection Agency Washington DC August 1986
EPA (US Environmental Protection Agency) 1986b Guidelines for the Health Risk Assessment ofChemical Mixtures EPA630R-98002 Risk Assessment Forum US EnvironmentalProtection Agency Washington DC Fed Regist 51(185)34014ndash34025 (September 241986) [Online] Available httpwwwepagovncearafrafguidhtm [December 27 2001]
EPA (US Environmental Protection Agency) 1986c Guidelines for Mutagenicity RiskAssessment EPA630R-98003 Office of Research and Development USEnvironmental Protection Agency Washington DC September 1986
EPA (US Environmental Protection Agency) 1989 Risk Assessment Guidance for SuperfundVol 1 Human Health Evaluation Manual (Part A) Interim Final EPA5401ndash89002Office of Emergency and Remedial Response US Environmental Protection AgencyWashington DC December 1989
EPA (US Environmental Protection Agency) 1991a Part V Guidelines for DevelopmentalToxicity Risk Assessment Notice EPA600R91001 Fed Regist
ADVANCES IN RISK ASSESSMENT SINCE THE ESTABLISHMENT OF THE PART503 RULE
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ompo
sed
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L fil
es c
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ed f
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inal
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m t
heor
igin
al ty
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tting
file
s P
age
brea
ks a
re tr
ue to
the
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inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
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ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
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tally
inse
rted
Ple
ase
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the
prin
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sion
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icat
ion
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e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
56(234)63798ndash63826 (December 5 1991)EPA (US Environmental Protection Agency) 1991b Risk Assessment Guidance for Superfund
Vol 1 Human Health Evaluation Manual (Part B Development of Risk-BasedPreliminary Remediation Goals) Interim EPA540R-92003 Office of Emergency andRemedial Response US Environmental Protection Agency Washington DC December1991
EPA (US Environmental Protection Agency) 1991c Risk Assessment Guidance for SuperfundVol 1 Human Health Evaluation Maual (Part C Risk Evaluation of RemedialAlternatives) Interim EPA540R-92004 Office of Emergency and Remedial ResponseUS Environmental Protection Agency Washington DC December 1991
EPA (US Environmental Protection Agency) 1992a Guidelines for Exposure AssessmentEPA600Z-92001 National Center for Environmental Assessment Office of Researchand Development US Environmental Protection Agency Washington DC Fed Regist57(May 29)22888ndash22938 [Online] Available httpwwwepagovnceawww1exposurehtm [August 1 2001]
EPA (US Environmental Protection Agency) 1992b Dermal Exposure Assessment Principles andApplications Interim Report EPA6008ndash91011B Office of Research and DevelopmentUS Environmental Protection Agency Washington DC [Online] Available httpwwwepagovnceadermalhtm [August 10 2001]
EPA (US Environmental Protection Agency) 1996a Proposed Guidelines for Carcinogen RiskAssessment EPA600P-92003C Fed Regist 61(79)17960ndash18011 (April 23 1996)[Online] Available httpwwwepagovnceawww1rafcra_prophtm [August 1 2001]
EPA (US Environmental Protection Agency) 1996b Guidelines for Reproductive Toxicity RiskAssessment EPA630R-96009 Office of Research and Development USEnvironmental Protection Agency Washington DC October 1996
EPA (US Environmental Protection Agency) 1996c Environmental Health Threats to ChildrenEPA175-F-96ndash001 Office of the Administrator US Environmental Protection AgencySeptember 1996 [Online] Available httpwwwepagovepadocschildhtm [August 12001]
EPA (US Environmental Protection Agency) 1996d Descriptive Statistics Tables from a DetailedAnalysis of the National Human Activity Pattern Survey (NHAPS) Data EPA600R-96148 Report prepared by AMTsang and NEKlepeis Lockhead MartinEnvironmental Service Company Las Vegas NV for National Exposure ResearchLaboratory Office of Research and Development US Environmental Protection AgencyLas Vegas NV July 1996
EPA (US Environmental Protection Agency) 1997a Exposure Factors Handbook Vol I II IIIEPA600P-95002Fa-c National Center for Environmental Assessment Office ofResearch and Development US Environmental Protection Agency [Online] Availablehttpwwwepagovnceaexposfachtm [July 31 2001]
EPA (US Environmental Protection Agency) 1997b Guiding Principles for Monte
ADVANCES IN RISK ASSESSMENT SINCE THE ESTABLISHMENT OF THE PART503 RULE
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is P
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ompo
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L fil
es c
reat
ed f
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er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Carlo Analysis EPA630R-97001 March 1997 National Center for EnvironmentalAssessment Office of Research and Development US Environmental ProtectionAgency [Online] Available httpwwwepagovnceamonteabshtm [April 2 2001]
EPA (US Environmental Protection Agency) 1997c Policy for Use of Probabilitistic Analysis inRisk Assessment at the US Environmental Protection Agency May 15 1997 NationalCenter for Environmental Assessment Office of Research and Development USEnvironmental Protection Agency [Online] Available httpwwwepagovnceamcpolicyhtm [April 2 2001]
EPA (US Environmental Protection Agency) 1998a Guidelines for Neurotoxicity AssessmentEPA630R-95001F Risk Assessment Forum US Environmental Protection AgencyWashington DC April 1998
EPA (US Environmental Protection Agency) 1998b Methodology for Assessing Health RisksAssociated with Multiple Pathways of Exposure to Combustor Emissions EPA 600R-98137 National Center for Environmental Assessment Office of Research andDevelopment US Environmental Protection Agency Cincinnati OH [Online]Available httpwwwepagovnceawww1combusthtm [December 26 2001]
EPA (US Environmental Protection Agency) 1998c Risk Assessment Guidance for SuperfundVolume I Human Health Evaluation Manual (Part D Standardized Planning Reportingand Review of Superfund Risk Assessments) Interim OSWER 92857ndash01D Office ofEmergency and Remedial Response US Environmental Protection Agency WashingtonDC
EPA (US Environmental Protection Agency) 1999a Risk Assessment Guidance for SuperfundVol 1 Human Health Evaluation Manual Supplement to Part A Community Involvementin Superfund Risk Assessments EPA 540-R-98ndash042 Office of Solid Waste andEmergency Response US Environmental Protection Agency Washington DC March1999 [Online] Available httpwwwepagovsuperfundprogramsriskragsaci-rahtm[December 26 2001]
EPA (US Environmental Protection Agency) 1999b Guidelines for Carcinogen Risk AssessmentNCEA-F-0644 Review Draft July 1999 National Center for Environmental AssessmentRisk Assessment Forum US Environmental Protection Agency Washington DC[Online] Available httpwwwepagovncearafcrasabhtm [September 13 2001]
EPA (US Environmental Protection Agency) 2000a Supplementary Guidance for ConductingHealth Risk Assessment of Chemical Mixtures EPA630R-00002 National Center forEnvironmental Assessment Office of Research and Development US EnvironmentalProtection Agency Washington DC August 2000 [Online] Available httpwwwepagovnceawww1rafchem_mixhtm [December 26 2001]
EPA (US Environmental Protection Agency) 2000b Water Biosolids Management andEnforcement Audit Report No 2000-P-10 Office of Inspector General March 20 2000[Online] Available httpwwwepagovoigearthauditlist30000P0010pdf [December20 2001]
EPA (US Environmental Protection Agency) 2000c Child-Specific Exposure
ADVANCES IN RISK ASSESSMENT SINCE THE ESTABLISHMENT OF THE PART503 RULE
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age
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inal
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brea
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tyle
s a
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type
setti
ng-s
peci
fic fo
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can
not b
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grap
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erro
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Ple
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as th
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e ve
rsio
n fo
r attr
ibut
ion
Factors Handbook (External Review Draft) NCEA-W-0853 National Center forEnvironmental Assessment Office of Research and Development US EnvironmentalProtection Agency Washington DC June 2000 [Online] Available httpwwwepagovnceawww1csefh2htm [December 26 2001]
EPA (US Environmental Protection Agency) 2000d Strategic Plan for the Analysis of theNational Human Exposure Assessment Survey (NHEXAS) Pilot Study Data EPA600R-00049 National Exposure Research Laboratory and National Center for EnvironmentalAssessment Office of Research and Development US Environmental ProtectionAgency Washington DC November 2000 [Online] Available httpwwwepagovNERLresearchnhexasstrategypdf [August 6 2001]
EPA (US Environmental Protection Agency) 2001a Risk Assessment Guidance for SuperfundVol 1 Human Health Evaluation Manual (Part E Supplemental Guidance for DermalRisk Assessment) Interim Review Draft EPA540R99005 OSWER 92857ndash02EPPB99ndash963312 Office of Emergency and Remedial Response US EnvironmentalProtection Agency Washington DC September 2001 [Online] Available httpwwwepagovsuperfundprogramsriskragseintroductionpdf [March 12 2002]
EPA (US Environmental Protection Agency) 2001b Risk Assessment Guidance for SuperfundVol 3- Part A Process for Conducting Probabilistic Risk Assessment EPA 530-R-02ndash002 PB2002 963302 Office of Emergency and Remedial Response US EnvironmentalProtection Agency Washington DC December 2001 [Online] Available httpwwwepagovoerrpagesuperfundprogramsriskrags3apdfcontprefpdf [May 21 2002]
EPA (US Environmental Protection Agency) 2001c Exposure Analysis for DioxinsDibenzofurans and CoPlanar Polychlorinated Biphenyls in Sewage Sludge TechnicalBackground Document Draft EPA Contract No 68-W6ndash0053 RTI 7600-OP3040Prepared by Center for Environmental Analysis Research Triangle Institute ResearchTriangle Park NC for the Office of Water US Environmental Protection AgencyWashington DC November 30 2001 [Online] Available httpwwwepagovwatersciencebiosolidsriskasdraftpdf [February 26 2002]
Evans JS JDGraham GMGray and RLSielken Jr 1994 A distributional approach tocharacterizing low-dose cancer risk Risk Anal 14(1)25ndash34
Finkel AM 1990 Confronting Uncertainty in Risk Management A Guide for Decision-MakersWashington DC Center for Risk Management Resources for the Future
Habicht HF 1992 Guidance on Risk Characterization for Risk Managers and Risk Assessors EPAMemorandum from EPA Deputy Administrator FHenry Habict III to AssistantAdministrators and Regional Adminstrators (Publish as pages 351ndash374 in Science andJudgment in Risk Assessment 1994 Washington DC National Academy Press)
Hertwich EG SFMateles WSPease and TEMcKone 2001 Human toxicity potentials for life-cycle analysis and toxics release inventory risk screening Environ Toxicol Chem 20(4)928ndash939
ADVANCES IN RISK ASSESSMENT SINCE THE ESTABLISHMENT OF THE PART503 RULE
161
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t th
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s ne
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rigin
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ork
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ompo
sed
from
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L fil
es c
reat
ed f
rom
the
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inal
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er b
ook
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fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Krewski D KSCrump JFarmer DWGaylor RHowe CPortier DSalsburg RLSielken andJVan Ryzin 1983 A comparison of statistical methods for low dose extrapolationutilizing time-to-tumor data Fundam Appl Toxicol 3(3)140ndash160
Melia RJW CDVFlorey SCDarby EDPalmes and BDGoldstein 1978 Differences in NO2levels in kitchens with gas or electric cookers Atmos Environ 12(6ndash7)1379ndash1381
Morgan GM MHenrion and MSmall 1990 Uncertainty A Guide to Dealing with Uncertaintyon Quantitative Risk and Policy Analysis Cambridge UK Cambridge University Press
Mumtaz MM and PRDurkin 1992 A weight-of-evidence approach for assessing interactions inchemical mixtures Toxicol Ind Health 8(6)377ndash406
NBP (National Biosolids Partnership) 2001 Manual of Good Practice for Biosolids Interim FinalDraft March 13 2001 [Online] Available httpbiosolids policynetproactivenewsroomreleasevtmlid=20961 [January 18 2002]
NRC (National Research Council) 1982 Risk and Decision Making Perspectives and ResearchWashington DC National Academy Press
NRC (National Research Council) 1989 Improving Risk Communication Washington DCNational Academy Press
NRC (National Research Council) 1993 Issues in Risk Assessment Washington DC NationalAcademy Press
NRC (National Research Council) 1994 Science and Judgement in Risk Assessment WashingtonDC National Academy Press
NRC (National Research Council) 1996 Understanding Risk Informing Decisions in a DemocraticSociety Washington DC National Academy Press
Pellizzari ED TDHartwell RLPerritt CMSparacino LSSheldon HSZelon RWWhitmoreJJBreen and LAWallace 1986 Comparison of indoor and outdoor residential levels ofvolatile organic chemicals in five US geographic areas Environ Int 12(6)619ndash623
PresidentialCongressional Commission on Risk Assessment and Risk Management 1997Framework for Environmental Health Risk Management Final Report Vol 1Washington DC The Commission
Schiffman SS JMWalker PDalton TSLorig JHRaymer DShusterman and CMWilliams2000 Potential health effects of odor from animal operations wastewater treatment andrecycling of byproducts J Agromed 7(1)7ndash81
Spengler JD CPDuffy RLetz TWTibbets and BGFerris Jr 1983 Nitrogen dioxide insideand outside 137 homes and implications for ambient air quality standards and healtheffects research Environ Sci Technol 17(3)164ndash168
Taylor AC JSEvans and TEMcKone 1993 The value of animal test information inenvironmental control decisions Risk Anal 13(4)403ndash412
Thomas KW EDPellizzari CAClayton RLPerritt RNDietz RWGoodrich WCNelsonand LAWallace 1993 Temporal variability of benzene exposures for residents in severalNew Jersey homes with attached garages or tobacco smoke J Expo Anal EnvironEpidemiol 3(1)49ndash73
ADVANCES IN RISK ASSESSMENT SINCE THE ESTABLISHMENT OF THE PART503 RULE
162
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t th
is P
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s ne
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ork
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ompo
sed
from
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L fil
es c
reat
ed f
rom
the
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inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
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ks a
re tr
ue to
the
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inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
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the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Wallace LA 1993 A decade of studies of human exposure What have we learned Risk Anal 13(2)135ndash139
Wilson JD 2001 Advanced Methods for Dose-Response Assessment Bayesian Approaches FinalReport based on a workshop held September 18ndash20 2000 Discussion Paper 01ndash15Resources for the Future Washington DC
ADVANCES IN RISK ASSESSMENT SINCE THE ESTABLISHMENT OF THE PART503 RULE
163
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ompo
sed
from
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es c
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fro
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heor
igin
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pese
tting
file
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age
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ks a
re tr
ue to
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inal
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e le
ngth
s w
ord
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ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
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ase
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his
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e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
5
Evaluation of EPArsquos Approach to Setting ChemicalStandards
The US Environmental Protection Agency used risk-assessment methodsto set biosolids chemical standards (termed ldquopollutant limitsrdquo under the Part 503rule) to be protective of human health and the environment Risk-basedstandards are generally maximum levels that should not be exceeded Risksexperienced by a typical receptor population are likely to be lower and in mostcases much lower than target risk levels used to derive risk-based standardsHowever the protectiveness of the risk-based standards is dependent on thedata and methods used to establish the standards as well as on compliance withspecified conditions of use
The risk-assessment methods for establishing the Part 503 rule weredeveloped in the mid-1980s Since that time EPA has refined risk-assessmentmethods and approaches and has issued a number of guidance documents tosupport standardized approaches to risk assessment (see Chapter 4) In thischapter the methods used for the Part 503 rule risk assessments are reevaluatedin light of the current practice of risk assessment Specific assumptions made inthe risk assessments are also reevaluated on the basis of available scientificinformation
Risk assessments typically include four steps hazard identificationexposure assessment toxicity (dose-response) assessment and riskcharacterization (NRC 1994) Elements of all four steps are considered in thefollowing sections The first section considers the hazard-identificationapproach used to select chemicals for inclusion in the risk assessment (EPA1985 1992ab) Subsequent sections address general issues for exposureassessment and risk
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 164
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fro
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heor
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al ty
pese
tting
file
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age
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ks a
re tr
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inal
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e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
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iden
tally
inse
rted
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ase
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t ver
sion
of t
his
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icat
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as th
e au
thor
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e ve
rsio
n fo
r attr
ibut
ion
characterization These sections are followed by a discussion of issues relevantto specific inorganic and organic chemicals including toxicity assessment
HAZARD ASSESSMENT AND CHEMICAL SELECTION
To date EPA has conducted two rounds of assessments to identifychemicals to regulate in the Part 503 rule Round 1 was conducted to identify aninitial set of chemical pollutants to regulate and Round 2 was conducted toidentify additional pollutants for regulation Standards for the Round 2pollutants have not been established but EPA is considering regulation ofdioxins (a category of compounds that has 29 specific congeners ofpolychlorinated dibenzo-p-dioxins polychlorinated dibenzofurans and coplanarpolychlorinated biphenyls) for land application Therefore although evaluationof EPArsquos dioxin risk assessments for biosolids is outside the scope of thecommitteersquos charge the committee believes that evaluating the selection ofdioxins for regulation is within the charge
Round 1 Pollutant Selection
EPA used a two-stage process to select its initial set of contaminants toregulate under the Part 503 rule First a list of chemicals was subjected to ahazard screening Second chemicals found to represent a potentially significantrisk were subject to formal risk assessment
In 1984 using available data on effects in humans plants domesticanimals wildlife and aquatic organisms and frequency of chemical occurrencein biosolids EPA identified 200 potential chemicals of concern in biosolids Apanel of scientific experts selected 50 chemicals of potential concern forevaluation by EPA A screening process was then used to select 22 pollutantsfor potential regulation (Table 5ndash1) The process involved developingenvironmental profiles for each pollutant for which data were readily availableon toxicity occurrence fate and pathway-specific hazards When relevantaggregate cancer risks from exposure via several pathways were assessed Risksposed by some of the pathways subsequently analyzed in the risk assessmentwere not used in the screening process (pathways 11ndash14 see Table 5ndash4 insummary of exposure pathways)
To determine whether a full risk assessment was warranted for a particularchemical via a specific exposure pathway a hazard index was calculated foreach contaminant and pathway that had sufficient data (EPA 1985) This indexis the ratio of the estimated concentration of the pollutant in the envi
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 165
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t th
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ompo
sed
from
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es c
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rom
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er b
ook
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heor
igin
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tting
file
s P
age
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ks a
re tr
ue to
the
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e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
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iden
tally
inse
rted
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ase
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his
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e au
thor
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e ve
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r attr
ibut
ion
TABLE 5ndash1 Pollutants Selected for Potential Regulation
Inorganic Chemicals Organic ChemicalsArsenic Aldrin and dieldrinCadmium Benzo[a]pyreneChromium ChlordaneCopper DDT DDD DDELead HeptachlorMercury HexachlorobenzeneMolybdenum HexachlorobutadieneNickel LindaneSelenium N-NitrosodimethylamineZinc Polychlorinated biphenyls
ToxapheneTrichloroethylene
Abbreviations DDT 111-trichloro-22-bis(p-chlorophenyl)ethane DDE 11-dichloro-22-bis(p-chlorophenyl)ethylene DDD 11-dichloro-22-bis(p-chlorophenyl)-ethaneSource EPA 1992a
ronment (soil plant or animal tissue water or air) to the establishedhuman health or other regulatory criteria (eg acceptable daily intake fornoncarcinogens or a cancer risk-specific intake) The calculated soilconcentrations were based on ldquotypicalrdquo and ldquoworstrdquo concentrations of thecontaminant found in biosolids and were evaluated at application rates of 5 and50 metric tons per hectare (mtha) and a cumulative application of 500 mthabased on the assumption of 5 mtha per year for 100 years Data onconcentrations of pollutants in sewage sludge were obtained primarily fromsurvey data collected in a 40-city study (EPA 1982) Median values were usedto represent typical concentrations and the 95th percentile was used torepresent the worst-case concentrations It is not clear how calculations ontypical concentrations and low application rates were used in the screeningprocess because the hazard index was reportedly derived using worst-caseconditions
After the screening process pollutants with a hazard index equal to orgreater than 1 were evaluated further The hazard index for each of thesepollutants was adjusted so that it reflected the hazard attributable only to
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 166
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t th
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ompo
sed
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heor
igin
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tting
file
s P
age
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ks a
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ue to
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e le
ngth
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ord
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eadi
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tyle
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ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
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grap
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erro
rs m
ay h
ave
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iden
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rted
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ase
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thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
biosolids for the specific pathway of exposure being evaluated This adjustmentwas done by excluding background exposure to the pollutant from sources otherthan biosolids When adjusted values exceeded 1 the pollutant was evaluatedfor that particular pathway in a detailed risk assessment Thus backgroundexposure was eliminated and only pollutants for which the hazard index wasgreater than 1 for the increment contributed by biosolids were subjected tofurther analysis through risk assessment This analysis assessed exposure viaeach pathway to each chemical For human-health-related pathways thisprocedure resulted in the elimination of fluoride and lindane from considerationin several pathways
After the proposed Part 503 rule was issued in 1989 EPA completed aNational Sewage Sludge Survey (NSSS) (EPA 1990) The NSSS collected dataon more than 400 pollutants from approximately 180 sewage treatment plantsthroughout the country to produce national estimates of concentrations ofpollutants in sewage sludge Using the NSSS data and information from the riskassessments EPA conducted a further screening analysis to eliminate fromregulation any pollutant that was not present at concentrations deemed to pose asignificant public health or environmental risk On the basis of this screeninganalysis the 12 organic chemicals were exempted leaving only inorganicchemicals for regulation by the Part 503 rule The following criteria forexempting organic pollutants were used
1 The pollutant has been banned from use has restricted use or is nolonger manufactured for use in the United States
2 The pollutant has a low frequency of detection in sewage sludge(less than 5) based on data from the NSSS
3 The concentration of the pollutant in sewage sludge is already lowenough that the estimated annual loading to cropland soil wouldresult in an annual pollutant-loading rate within allowable risk-based levels
Aldrin and dieldrin chlordane 111-trichloro-22-bis(p-chlorophenyl)ethane 11-dichloro-22-bis(p-chlorophenyl)ethylene 11-dichloro-22-bis(p-chlorophenyl)ethane (DDT DDE DDD) heptachlor lindane N-nitrosodimethylamine polychlorinated biphenyls (PCBs) and toxaphene wereeliminated on the basis of criterion 1 All the organics except aldrin anddieldrin bis(2-ethylhexyl)phthalate and PCBs met criterion 2 On the basis ofagricultural application assumptions all the organics except benzo[a]pyrenehexachlorobenzene N-nitrosodimethylamine and PCBs met criterion 3 Underdifferent application scenarios some of these same organics might not meetcriterion
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 167
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t th
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er b
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heor
igin
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tting
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age
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ks a
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e le
ngth
s w
ord
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ks h
eadi
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tyle
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ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
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rted
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itativ
e ve
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r attr
ibut
ion
3 For example EPA (1992b) noted that under scenarios for applications toforests and public contact sites toxaphene and the organics eliminated under theagricultural scenario do not meet criterion 3
Round 2 Pollutant Selection
Subsequent to the promulgation of biosolids regulations in 1993 anotherevaluation was conducted to develop a list of Round 2 pollutants to consider forregulation (EPA 1996a) As with the Round 1 pollutants EPA conducted apreliminary hazard identification followed by a risk assessment for thosecontaminants and pathways identified as potential hazards In this evaluationdegradation products of organic contaminants were assumed to be nontoxicThe list of 411 pollutants analyzed in the NSSS (EPA 1990) was the startingpoint of the Round 2 assessments Pollutants were eliminated fromconsideration if they were not detected (254 pollutants) or were detected in lessthan 10 of sewage sludge (69 pollutants) Pollutants present in more than 10of sewage sludge but with insufficient toxicity data were also eliminated fromRound 2 consideration (see Table 5ndash2) Some of these chemicals lack toxicityvalues due to a relative lack of toxicity Several pollutants were grouped intoclasses of congeners (eg PCBs chlorinated dioxins and furans)
The screening process identified 30 pollutants that had a frequency ofdetection of 10 or greater in the NSSS and that had data on human health andor ecological toxicity (Table 5ndash3) Asbestos which was not analyzed in theNSSS was added as another potential candidate for regulation because it istoxic persistent and can be in biosolids These 31 pollutants were subject tofurther analysis in a comprehensive hazard identification study The study useda mix of conservative and average value assumptions similar to those used inthe Round 1 risk assessments The aggregate exposure through more than onepathway was not assessed Analysis of a particular pathway of exposure forcertain candidate chemicals was not conducted when EPA determined thatchemical-specific data were insufficient for that pathway The result of theevaluation was that only dioxins furans and coplanar PCBs (considered as agroup) were subject to further risk assessment (EPA 1996a) That riskassessment led to a proposed standard in December 1999 (EPA 1999a) EPAsponsored a peer review of that risk assessment and proposed standard (Versar2000) On the basis of review comments and the agencyrsquos reassessment ofdioxin risks EPA decided to revise the risk assessment A peer-review draftwas released November 30 2001 (EPA 2001a) and a notice of data availabilitywas subsequently issued for public comment on June 12 2002 (EPA 2002)
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 168
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ompo
sed
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heor
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tting
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age
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ks a
re tr
ue to
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inal
lin
e le
ngth
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ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
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iden
tally
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rted
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ase
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prin
t ver
sion
of t
his
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e au
thor
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e ve
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r attr
ibut
ion
TABLE 5ndash2 Chemicals Eliminated from Consideration in the Round 2 AssessmentsBecause of Lack of Toxicity DataCalcium MagnesiumDecane n- Octacosane n-Dodecane n- SodiumEicosane n- Tetracosane n-Hexacosane n- Tetradecane n-Hexadecane n- Triacontane n-Hexanoic acid YttriumIron
Source EPA 1996a
Limitations of the Assessment and Selection Process
Survey Data
Accurate data on pollutant concentrations in biosolids are crucial to theselection of chemicals to regulate under the Part 503 rule Many of the decisionsmade in the chemical selection process were based on concentration data fromthe NSSS (EPA 1990) The NSSS was an ambitious undertaking and providesthe most comprehensive data on the content of sewage sludge in the UnitedStates to date However the survey was conducted over a decade ago and thereis a need to conduct a new survey to characterize the concentrations anddistribution of chemicals now present in biosolids For example state surveydata presented in Chapter 2 show that concentrations of some of the regulatedinorganic elements have generally decreased over the past decade Furthermorethe accuracy of the NSSS data was called into question by an earlier NRCcommittee that was asked to evaluate the use of biosolids on croplands (NRC1996) That committee found inconsistencies in the surveyrsquos sampling analysesand data-reporting methods that undermined the reliability of the dataTherefore it recommended that another comprehensive survey be conducted torectify the NSSSrsquos sampling and analytical limitations To date no such surveyhas been done
Some chemicals that were undetected because of analytical problems ordetection limits that exceeded risk-based concentrations were likely eliminatedmistakenly Each of the chemicals in the NSSS was assigned a ldquodetectionlimitrdquo which was equivalent to the minimum concentration of pollutant thatcould be quantitated (EPA 1990) The detection limits are difficult to discern
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 169
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tting
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ord
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eadi
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tyle
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nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
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e ve
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ibut
ion
TABLE 5ndash3 Candidate Pollutants for Round 2 Regulationsa
Acetic acid (24-dichlorophenoxy) Methylene chlorideAluminumb NitrateAntimony NitriteAsbestosc PentachloronitrobenzeneBarium PhenolBeryllium Polychlorinated biphenyls-coplanarBis(2-ethylhexyl)phthalate Propanone 2-Boron Propionic acid 2-(245-trichlorophenoxy)Butanone 2- SilverCarbon disulfide ThalliumCresol p- TinCyanides (soluble salts and complexes) TitaniumDioxins and dibenzofurans TolueneEndosulfan-II Trichlorophenoxyacetic acid 245-Fluoride VanadiumManganese
aPollutants detected at a frequency of at least 10 with human health andor ecological toxicity dataavailablebAluminum does not have human health or ecological toxicity data available but is included becauseof its potential for phytotoxicitycAsbestos was not tested in the NSSS but is toxic persistent and can be in sewage sludgeSource EPA 1996a
from the NSSS data and actual detection limits for a given chemicalvaried over a wide range of concentrations among samples (Figures 5ndash1through 5ndash4) Data presented in the technical support document for the Round 2assessment (EPA 1996a) indicated that some detection limits exceeded severalhundred parts per million for some of the organic chemicals At the request ofthe committee detection limits of NSSS samples for eight chemicals four ofwhich were not detected in the NSSS (ideno[123-cd]pyrene N-nitrosodimethylamine pentachlorophenol and toxaphene) were provided byEPA (Charles White EPA personal communication February 2001) Beforeconducting a risk assessment the adequacy of the available chemicalconcentration data to support the risk assessment is typically evaluated (EPA1991) It is
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FIGURE 5ndash1 Detected concentrations ( ) and detection limits (times) fornondetects (as a function of solids content of sewage sludge) compared withsiol screening levels (A ingestion and dermal B inhalation) forhexachlorobenzene and mercury Source NSSS data from EPA 1990
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FIGURE 5ndash2 Detected concentrations ( ) and detection limits (times) fornondetects (as a function of solids content of sewage sludge) compared withsoil screening levels (A ingestion and dermal) for indeno(123-cd)pyrene andPCB-1254 Source NSSS data from EPA 1990
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FIGURE 5ndash3 Detected concentrations ( ) and detection limits (times) fornondetects (as a function of solids content of sewage sludge) compared withsoil screening levels (A ingestion and dermal) for toxaphene andpentachlorophenol Source NSSS data from EPA 1990
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FIGURE 5ndash4 Detected concentrations ( ) and detection limits (times) fornondetects (as a function of solids content of sewage sludge) compared withthe soil screening levels for dieldrin and the EPA Region 9 preliminaryremediation goal (A ingestion and dermal) and for N-nitrosodimethylamine(B ingestion) (EPA 2002b) Note The PRG for N-nitrosodimethylamine isapproximately 1 microgkg and could not be shown grapically on the figureSource NSSS data from EPA 1990
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current risk-assessment practice to evaluate the adequacy of analyticaldetection limits by comparing them with conservative risk-based screeningconcentrations (RBCs) For example EPA (2001b) has developed soilscreening levels (SSLs) which are based either on incidental ingestion of anddermal contact with soil or on inhalation of vapors or resuspended soilparticulates Figures 5ndash1 through 5ndash4 show chemical concentrations anddetection limits for selected chemicals in sewage sludge as a function of thepercent solids in the sample (elevated detection limits were sometimesassociated with low percent solids) These values compared with the SSLs1
show that for some of those chemicals most sample detection limits exceed thelowest SSL Thus the NSSS failed to achieve sufficient detection for four of theeight chemicals selected as examples to determine whether they were presentat concentrations requiring further evaluation in a risk assessment
Data regarding detection frequency were used to make critical decisions inRounds 1 and 2 For example chemicals were eliminated from consideration inRound 1 if they were detected at a frequency of less than 5 in the NSSS (EPA1992a) and in Round 2 if detected at a frequency of less than 10 (EPA 1996a)On a national scale a 10 elimination criterion might seem reasonablehowever because of the local use of most biosolids that criterion couldoverlook potentially significant site-specific risk
NSSS data were also used in calculating the hazard screening indexes thatdetermined whether a chemical would be evaluated in a risk assessment Forexample some organic chemicals were excluded from regulation because theirconcentrations in biosolids were already low enough and their estimated annualloading to cropland soil would result in an annual pollutant loading rate withinallowable risk-based levels EPA compared the annual pollutant loading rate(APLR) of a specific chemical based on its 99th percentile concentration in theNSSS with the annual pollutant loading concentrations calculated by the Part503 exposure assessment If the 99th percentile concentration of a pollutantresulted in an APLR less than the loading rate calculated through the risk-basedexposure assessment EPA did not regulate the pollutant However as noted bythe 1996 NRC committee the 99th percentile concentrations of four pollutants(PCBs benzo[a]pyrene hexachlorobenzene and N-nitrosodimethylamine)resulted in calculated APLRs higher than those calculated by the exposureassessment (NRC 1996) The four compounds were eliminated from regulationbecause they were either no longer manufactured
1When an SSL was unavailable the EPA Region 9 preliminary remediation goal wasused
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(PCBs and N-nitrosodimethylamine) or had a low frequency of detection in theNSSS (benzo[a]pyrene and hexachlorobenzene) If these pollutants are presentin biosolids at concentrations approaching the 99th percentile they can posemore of a risk than would be considered acceptable in the exposure assessment
Additional Chemicals of Potential Concern
A number of contaminants not included in the NSSS have since beenidentified as biosolids pollutants Some of these chemicals enter wastewaterfrom industrial releases but analyses for them are not routinely conductedwhereas other chemicals entering wastewater primarily from domestic releasesare not typically included in environmental analyses which usually focus onindustrial chemicals found at hazardous waste sites
Some categories of chemicals such as pharmaceuticals personal-careproducts and chemicals added to condition and dewater sewage sludge that areespecially likely to be present in domestic sewage remain unstudied inbiosolids Only a few studies have been conducted on the wide variety ofodorants present in sewage sludge New data described below and otherconsiderations demonstrate the need for a new hazard assessment of biosolids toexpand the suite of chemicals evaluated Some categories of pollutants inaddition to those mentioned above that should be considered in futureassessment are discussed later in this chapter in the section Organic Chemicals
The Toxics Release Inventory which tracks the release of over 600pollutants that are discharged by businesses meeting certain thresholdsdocuments that pollutants continue to be released to sewer systems fromindustrial and commercial sources Although data on a core set of chemicalstracked consistently between 1988 and 1999 show that transfers to publiclyowned treatment works (POTWs) substantially decreased (for example transferof metals decreased by 65) trend data between 1995 and 1999 indicate atransfer increase for all tracked chemicals of about 76 to POTWs withgreater increases for tracked metals2 (EPA 2001c) Over the same periodwastewater flows into sewage treatment plants and sewage sludge volumesincreased approximately 85 (calculated based on data in Appendix A of EPA[1999b])
2Transfers of tracked TRI metals increased 31 during this four-year period It shouldbe noted that the tracked metals are not the same as the inorganic chemicals regulatedunder the Part 503 rule
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This suggests that overall industrial discharges to POTWs are increasing at asimilar rate as sewage sludge volumes
Under the Clean Water Act EPA is required to review the regulations inPart 503 at least every 2 years to identify additional toxic pollutants andpromulgate regulations for such pollutants (33 USC Section 1345(d)(2)(C)) Anew hazard assessment should include review of new studies from the UnitedStates Canada Europe and elsewhere to identify additional pollutants to beevaluated In addition to evaluating more industrially used chemicalsconsideration must be given to identifying and characterizing nonindustrialchemicals that are released into sewer systems (eg pharmaceuticals andpersonal-care products) or added to wastewaters during treatment processes(eg dewatering agents)
Data Gaps
Some pollutants and exposure pathways were eliminated in the screeningprocesses and risk assessments when chemical-specific data were insufficient toperform pathway-specific calculations or when toxicity data were insufficientfor a given pollutant For example a plant uptake factor for lindane was notavailable so no assessments were conducted for any pathway that relied on thatfactor Thus the potential risks from lindane via those particular pathways werenot assessed The technical support documents for EPArsquos Round 1 and Round 2assessments do not provide a list of data gaps nor do they specify the chemicalsand pathways that were eliminated from consideration because of data gapsThe lack of that information makes it impossible to identify the implications ofthe data gaps Lack of information does not equate to lack of risk Thereforedata gaps should not be used as a criterion for eliminating chemicals fromconsideration but should be used to identify important areas for future research
In conclusion new studies of the contaminant concentrations in biosolidsshould include evaluation of pollutants such as surfactants flame retardantsand pharmaceuticals not included in previous surveys Biosolids should bemonitored periodically as new pollutants are identified and analytical methodsimproved As analytical methods are identified risk-based screeningconcentrations should be used to ensure that detection limits are adequate tosupport risk assessment Use of a lower frequency of detection to eliminatecontaminants from regulation should be considered Data gaps that result in theinability to assess risks need to be identified so that research can be conductedto fill those gaps
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EXPOSURE ASSESSMENT
As described in Chapter 4 exposure assessment is the identification andquantification of potential exposures For exposure to chemicals to occur acomplete exposure pathway must exist A complete pathway requires thefollowing elements (EPA 1989)
bull A source and mechanism for release of chemicalsbull A transport or retention mediumbull A point of potential human contact (exposure point) with the affected
mediumbull An exposure route at the exposure point
These elements are typically identified in a conceptual site model If anyone of these elements is missing the pathway is not considered complete Forexample if human activity patterns and the location of human populationsrelative to the location of an affected medium prevent human contact then thatexposure pathway is not complete One of the primary differences between thePart 503 rule risk assessment and current risk-assessment practice is that thePart 503 rule risk assessment derived separate risk-based levels for eachindividual exposure pathway evaluated whereas current practice is to performaggregate risk assessments in which risk-based standards are derived afteraggregation of exposures by all pathways to which a single individual is likelyto be exposed
EPA has used a conceptual site model in a new analysis of risks associatedwith dioxins in biosolids (EPA 2001a) The conceptual site model used by EPAfor agricultural application is shown in Figure 5ndash5 A number of importantassumptions that may be questioned are embedded in such a model (eg thenotion of the buffer zone) However this figure provides an example of how aconceptual site model illustrates the mechanisms by which contaminants inbiosolids are transported from the site of application to a point of contact with ahuman receptor For each category of receptor identified exposures from allidentified pathways are summed to provide an estimate of total exposures
This section reviews the approach used by EPA to select exposurepathways for the Round 1 Part 503 rule risk assessment describes current EPAexposure-assessment procedures (focusing on multipathway risk assessment)and then attempts to assess the implications of the differences in current versushistorical approaches The final section reviews and compares the historical andcurrent exposure assumptions for pathway-specific parameters and examinesmethodological issues for derivation of some chemical-specific parameters
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FIG
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E 5
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EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 179
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Summary of Approach Used to Select Exposure Pathways
The Part 503 risk assessment evaluated 14 exposure pathways 9 of whichincluded human pathways (Table 5ndash4) The human exposure pathways considerdirect ingestion of biosolids by a child ingestion of produce grown on biosolids-amended soil by either a home gardener or consumers buying the produce instores ingestion of animal products derived from livestock exposed via food orsoil ingestion inhalation by a farmer of dust or inhalation of vapors containingchemicals released from biosolids-amended soils and ingestion of fish andwater affected by release of chemicals from amended soils Although thesepathways may include the primary exposure pathways for a resident nearbiosolids-amended fields EPA did not identify a single common receptor andcalculate exposures in such a way that exposure via multiple pathways could beadded The conservatism in the exposure assumptions varies widely in the Part503 rule risk assessment The variability in the conservatism of the assumptionsfor the various pathways results in the highest risks being associated with thepathway with the most conservative assumptionsmdashthat is the child ingestingundiluted biosolidsmdashrather than the pathways most likely to contribute toexposures A more robust assessment of potential exposures to contaminants inbiosolids would be provided by an aggregate assessment of total exposuresfrom all pathways that a single receptor is likely to encounter Although it islikely that one or two pathways will be the dominant contributors to exposurefor any one chemical the dominant pathways may vary with chemicals and arenot always correctly predicted before conducting the risk assessment
Description of Conceptual Model and Exposure ScenarioApproach
For each biosolids-application scenario being evaluated a conceptualmodel should be developed to describe the scenarios under which exposurescould occur Agricultural forestry and land-reclamation applications may allresult in somewhat different conceptual models A conceptual site model shouldidentify the biosolids source (eg biosolids tilled into soil or applied to thesurface for agricultural soils) the pathways by which biosolids constituents maybe released and transported and the nature of human contacts with theconstituents The limitations of the assessment should be clearly articulated(eg whether exposures are evaluated only after land application) and anyexclusion of exposures associated with processing and transporting biosolidsshould be reported
The conceptual site model developed for the risk assessment for dioxins inbiosolids (EPA 2001a) provides an illustration of this approach for the
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 180
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TA
BL
E 5
ndash4 E
xpos
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Ass
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hway
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ioso
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ioso
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Eco
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Hum
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ioso
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ound
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uman
Sour
ce E
PA 1
995
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 181
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agricultural application scenario Although some of the assumptions of thesite model are open to question the model is clearly laid out The dioxin riskassessment examines exposures of two primary kinds of human receptors afarm family living adjacent to and downhill from the land-application site (in anarea termed a buffer) and a recreational fisher catching fish from a streamdownhill from the land-application site For the farm family aggregateexposures by the following pathways are assessed
bull Incidental ingestion of soil in the bufferbull Ingestion of above- and below-ground produce grown on croplandbull Ingestion of beef and dairy products from a pasturebull Ingestion of home-produced poultry and eggs from the bufferbull Inhalation of ambient air (particulates and vapor)bull Ingestion of motherrsquos milk by an infant
Only chronic exposures to dioxins are evaluated and one pathway(groundwater ingestion) considered in setting the Part 503 standards isexcluded The inclusion of some pathways and exclusion of others in thisfocused risk assessment reflects both assumptions about the exposure such asthe absence of a farm pond used for fishing and the expected behavior of thechemicals being evaluated Dioxins dibenzofurans and coplanar PCBs arepersistent lipophilic chemicals that are expected to partition into meat eggs andmilk but are not expected to leach to groundwater Similarly the focus onchronic exposures is appropriate for persistent chemicals present in biosolids inlow concentrations
In developing a conceptual site model that could form the foundation for amultipathway risk assessment for a great variety of chemicals it is necessary tothink more broadly about the exposure pathways and exposure durations to beevaluated Consequently groundwater ingestion and short-term exposures tovolatile chemicals should be included in a biosolids risk assessment Similarlydifferent application practices such as forestry land reclamation or directapplication of biosolids to home gardens by consumers would require separateconceptual site models
Evaluation of Exposure Models and Parameters
Estimation of potential exposures to chemicals for the purpose of derivingrisk-based concentrations requires theoretical calculations based onunderstanding how people come into contact with chemicals in environmentalmedia and how chemicals move among various environmental media Thesecalculations include assumptions for many parameters beginning with fate and
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 182
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transport models for predicting chemical concentrations in the exposure mediaSome of the assumptions for each of the pathways evaluated in the Part 503 rulerisk assessment are presented in Table 5ndash5 Working backward from landapplication of biosolids it is necessary to predict chemical concentrations insoil in plants grown in the soil in livestock grazed in the fields or fed foragefrom the fields and in other media identified in the various exposure pathwaysOnce chemical concentrations in the exposure media are estimated assumptionsmust be made about the values of other parameters that control the degree ofexposure to the media Some of these parameters are specific to the exposurepathway being evaluated For example to evaluate incidental ingestion ofchemicals in soil an assumption must be made about the amount of soil aperson will ingest Other parameters are chemical specific such as the relativebioavailability of a chemical in soil
In addition several management requirements in the Part 503 rule couldaffect predicted chemical concentrations in exposure media The riskassessments assume compliance with those requirements Managementrequirements and compliance with them are discussed in more detail inChapter 2 The committee found that EPA does not have an adequate programfor ensuring compliance with those requirements Some of the criticalmanagement practices and assumptions are discussed in Box 5ndash1
As discussed in Chapter 4 there have been several important advances inrisk assessment since the Part 503 rule was promulgated One of the mostsignificant advances in exposure assessment has been the development ofprobabilistic risk assessment methods that provide a quantitative description ofvariability and uncertainties in exposure estimates (EPA 2001d) EPArsquos mostrecent risk assessment for dioxins in biosolids (EPA 2001a) includes bothdeterministic and probabilistic risk assessments In the following sections themethods and assumptions used to identify exposure parameters in the Part 503rule risk assessment are reviewed in light of those advances The assumptionsmake use of scientific data and knowledge but policy decisions are inherent inmaking choices about what estimates to use While general issues related toexposure parameters are addressed specific values are not recommendedbecause such values must be identified in the context of the risk assessmentbeing conducted Similarly no recommendation is made regarding usingdeterministic or probabilistic approaches because the relative utility of theseapproaches varies (EPA 2001d)
HEI Receptor Versus RME Receptor
One of the most critical policy decisions in conducting the biosolids riskassessments was the decision to use the highly exposed individual (HEI) as the
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 183
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EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 184
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EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 185
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BOX 5ndash1 MANAGEMENT PRACTICES AND ASSUMPTIONS
Management Practices
bull Biosolids shall not be applied to land if it is likely to adversely affect athreatened or endangered species or its designated critical habitat
bull Biosolids cannot be applied to flooded frozen or snow-covered land insuch a way that bulk biosolids enter a wetland or other waters of theUnited States unless allowed in a permit The implementation of thisrequirement is unclear
bull A 10-meter setback from watercourses is required for biosolids notmeeting Class A and vector attraction reduction requirements andpollutant-concentration limits
bull Regulations require that bulk biosolids be applied to agricultural fieldsforests and public contact sites at a rate equal to or less than thenitrogen-based agronomic rate This requirement also applies toreclamation sites unless otherwise approved by the permit authority Itis not applicable to bagged products or bulk application of Class Abiosolids meeting pollutant-concentration limits
Management Assumptions
bull EPA (1992a) states that surface application is normally limited toslopes of 6 or less to reduce surface runoff That is not arequirement and how or whether that slope limitation was used in thebiosolids risk assessments is unclear
bull Field storage of biosolids at the site of land application is a commonpractice that is allowed under the Part 503 rules Recognizing thepotential for stockpiling and field storage to cause problems includingodors EPA developed nonregulatory guidance (EPA 2000a) The Part503 risk assessments and rules do not address stockpiling
bull Tile drains (drainage pipes installed at shallow depths in agriculturalfields) are common in some portions of the United States Designed todry out soils these drains provide conduits for the rapid movement ofcontaminants from land-applied biosolids into surface waters The Part503 risk assessments and rules did not consider the potential for thistype of exposure
bull Different methods of biosolids application are not addressed and mayhave different implications for risks particularly those associated withairborne emissions
receptor of concern (EPA 1992a) The HEI is an individual who remainsfor an extended period at or adjacent to the site where maximum exposureoccurs Current practice is to use a reasonable maximum exposure (RME)receptor EPA (1989) specifies that calculation of the RME in a deterministicrisk assessment requires a combination of average and upper-bound values forvari
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 186
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ng-s
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ous exposure parameters so that the final exposure estimate will be an upper-bound exposure with a reasonable expectation of occurrence This calculation iscommonly interpreted to be a 90th to 95th percentile of exposures for eachpathway For some exposure pathways the use of more than one or two upper-bound exposure parameters might result in exposure estimates with noreasonable expectation of occurrence Thus the impact of multiple conservativeassumptions must be evaluated carefully For probabilistic risk assessmentrisks corresponding to the 90th to 999th percentiles of the risk distribution areconsidered plausible high-end risks for selection of the RME (EPA 2001d)However EPA notes that very high percentiles may be numerically unstableand should only be used if reproducible
The goal of the Part 503 rule is to establish pollutant limits that areprotective of reasonably anticipated adverse effects But this standard should beapplied to all settings to all biosolids and to all land-application practices thatare reasonably anticipated to occur That goal necessitates assessing risks underthe most sensitive exposure setting that is likely to occur For example a farmfamily living near a land-application site may produce much of their own foodand have exposures via multiple pathways In addition parameters that arelinked should be identified and those links should be maintained throughout therisk assessment For example in the revised risk assessment for dioxins inbiosolids (EPA 2001a) dioxin and PCB congener data were linked withinsamples and those links were maintained throughout the probabilistic riskassessment
Determination of Chemical Concentrations in Exposure Media
Most of the exposure pathways evaluated by EPA require that chemicalconcentrations be estimated in one or more exposure media The exposuremedia for which concentrations were estimated in the Part 503 rule riskassessment are soil plants livestock airborne dust vapors surface water fishand groundwater Estimates of chemical concentrations in those media arebased on a number of assumptions such as assumptions about chemical fateand transport This section reviews one of the more important assumptionsabout chemical fate (mass balance and distribution of contaminants) andevaluates EPArsquos approach to estimating concentrations in environmental mediaSpecial emphasis is given to the determination of soil and plant concentrationsThis section is followed by a brief assessment of assumptions about humanintake parameters
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 187
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Mass Balance and Distribution of Contaminants
For pathways involving exposure via surface water air or groundwater(Pathways 12ndash14 Table 5ndash5) losses of pollutant mass from soil due topartitioning to other media are assumed by EPA For example pollutant masslosses from soil are assumed to occur to surface water through erosion to airthrough volatilization and to groundwater through leaching For organicchemicals it is assumed that degradation occurs and that degradation productsare nontoxic an assumption that is not universally true In assessing risk viathese pathways the assumption is made that pollutant mass is conserved Thusfor example the amount of a pollutant in sediment eroded from a site isadjusted to account for the amount that is predicted to be removed because ofleaching degradation and volatilization Many of these estimates are based onmodels that make a number of assumptions on scant data resulting in a highdegree of uncertainty For example data on partition coefficients for specificchemicals were based on a single study of only one type of biosolids (seediscussion below)
Soil Concentrations
Most of EPArsquos exposure pathways begin with estimated soilconcentrations resulting from the mixing of biosolids into soil the exceptionsbeing Pathway 3 (inadvertent direct ingestion of biosolids) and Pathway 5(biosolids applied to pastures and not mixed with soil) Consequently theaccuracy of the exposure assessment is highly dependent on the accuracy of thepredicted soil concentrations These predictions are based on assumptionsregarding the incorporation of biosolids into soil and the depth of theincorporation chemical retention in soils and the frequency duration andloading rates of application
Incorporation In exposure scenarios in which biosolids are incorporatedinto soil EPArsquos risk assessment assumed a tillage depth of 15 centimeters (cm)The revised dioxin risk assessment assumes 20 cm (EPA 2001a) However 10cm has been proposed as a more realistic figure when biosolids are incorporatedby disking rather than plowing (Versar Inc 2000) and for home gardens handtillage could be shallower than 15 cm Surface application withoutincorporation is typical in some scenarios such as pasture-land application orconservation tillage
Retention Inorganic chemicals in biosolids were assumed to stay in soilfor all pathways except Pathways 12ndash14 where a mass-balance approach was
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 188
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used to predict soil concentrations Retention or release of metals and organiccontaminants in soils is highly dependent on the characteristics of thecontaminants the mineralogical composition of the biosolids and the soil towhich it is applied and the pH wetting and drying and ionic strength of thesoil solution
Soils that are sandy and that contain low amounts of clay and organicmatter (eg those in the Atlantic Coastal Plain Region) will have less capacityto retain metals and organic chemicals than those that have high amounts ofclay and organic matter The latter soils are often accompanied by metal oxidecoatings electrostatically bound to the clay minerals and organic matterenhancing the soilrsquos ability to retain contaminants In higher clay and organic-matter soils metals and organic chemicals can be strongly bound and resistantto release into groundwaters Organic matter is especially important in theretention of organic contaminants
In many instances an ldquoagingrdquo effect is observed with metals oxyanionsand organic chemicals in soilsmdashthat is the longer the time of contact betweenthe contaminant and the soil the more sequestered the contaminant It is welldocumented that with many organic chemicals the release of the chemical andits bioavailability is greatly diminished as time in soil increases (Alexander2000 Pignatello 1999 Young et al 2001) The aging effect with organicchemicals has been largely ascribed to interparticle diffusion into the organicmatter of the soil The aging effect has also been observed with such metals ascadmium zinc cobalt and nickel (Barrow 1998 McLaren et al 1998 Scheckelet al 2000) This effect has been attributed to diffusion into the inorganiccomponents of the soils inner-sphere complex interactions and surfaceprecipitation It should not be assumed that the aging effect precludes release ofchemicals from soil For example certain metals including cadmiummolybdenum and zinc show continued availability for plant uptake frombiosolids-amended sites despite aging (McBride et al 1997 McGrath et al2000 Broos et al 2001)
The aging effect must be considered when predicting the fate ofcontaminants in biosolids in soils and waters Traditionally partitioncoefficients (Kps) are based on a 24-h reaction time however if the rates ofretention and release are slow and a residence time effect is pronounced the Kpvalues can be greatly underestimated when a 24-h reaction time is assumed inthe calculation Consequently the mobility of the contaminant would beoverpredicted
Application Rates and Duration The Part 503 rule addresses severalapplication scenarios including agricultural use silvicultural use and landreclamation Different biosolids-application techniques are used in thesescenarios and can affect the resulting contaminant concentrations in soils Forexample the rate of application at reclamation sites is usually much higher
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 189
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TABLE 5ndash6 Estimated Biosolids Application Rates for Different Scenarios
Scenario Number ofObservations
MeanApplicationRate (metrictonshay ofDW)
StandardDeviation
75thPercentile(metrictons hayof DW)
Agricultural 87 68 105 16Forest 2 26 26 34Public contact 11 19 122 125Reclamation 7 74 148 101
Abbreviation DW dry weightSource EPA 1992b
than that at agricultural sites although reclamation applications typicallyinvolve one-time or limited-time applications rather than repeated applicationsEstimates of application rates were based on data from the NSSS (EPA 1990)and are presented in Table 5ndash6 The number of applications before regulatorycumulative pollutant loading rates are reached at these application rates isapproximately 13 32 55 and 100 years for reclamation public contact forestand agricultural uses respectively (EPA 1992a) EPA based its chemicalstandards on the scenario of biosolids application to agricultural land for 100years which was considered applicable to the other types of land applicationsthat would not occur as routinely or for as long a duration
Plant Concentrations
Plant uptake of metals from biosolids-amended soils is another importantfactor in several of the exposure pathways To determine plant uptake EPA(1992a) derived plant uptake coefficients (UCs) for each pollutant A UC is theuptake-response slope of a pollutant in plant tissue for each food group and isestimated by the increase in pollutant in plant tissue for each kilogram ofpollutant added to the soil from biosolids Five main steps were used to estimateUCs (1) the primary literature was reviewed and evaluated (2) the relevantdata were compiled in a database (3) the uptake slope for each study wascalculated by linear regression of the concentration of the pollutant in planttissue against the application rate of the pollutant (4) the plants were placed incategories (eg leafy vegetables and garden fruits) and (5) the uptake slope ofeach plant group was calculated for each pollutant by using the geometric meanof the uptake slopes from relevant studies
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 190
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The likely concentrations of the pollutant in food groups were thencalculated for the risk assessment by using information on the amount of soilcontamination and the UC Data for those calculations were derived from threecategories of studies (1) field studies of biosolids (2) non-field studies ofbiosolids (greenhouse or potted) or field studies with biosolids spiked withadditional metals and (3) studies of metal salts metal-contaminated soils ormine tailings Obviously the first category of studies was the most relevant tothe risk assessments Studies have unequivocally demonstrated that greenhouseor potted plants and added inorganic metal salts do not mimic the characteristicsof metals within biosolids Such studies are irrelevant to real land application ofbiosolids For the metals regulated on the basis of human health the UCs werebased on field studies for cadmium field and nonfield studies for selenium andmercury and primarily studies of metal salts metal-contaminated soils or minetailings for arsenic
Factors affecting the estimates of UCs and limitations in the UCs selecteddue to the variation in bioavailability of metals to plants in different situationsare discussed below
Plant Response to Metals Some field-plot experiments with biosolidsshow that plant concentrations of some metals do not increase with high rates ofbiosolids application (Corey et al 1987 Mahler et al 1987 Chancy and Ryan1994) EPA (1992a 1995) attributes that observation to the binding of metalsby biosolids and uses it to support the concept of a plateau response in plantuptake (The rate of pollutant uptake by plants in the biosolids-soil mixturedecreases with increasing biosolids loadings because adsorptive materials inthe biosolids become as important as or more important than the adsorptivematerials initially in the soil) One of the main limitations of the availabledatabase is that the data are insufficient to separately characterize the changes inuptake with the metal concentration at a constant biosolids loading rate ascompared with the changes in uptake with increasing biosolids loadingAccurate prediction of plant concentrations requires both characterizations
EPA used a linear-response rather than a plateau-response assumption forthe low biosolids loading linear portion of the uptake curve in its riskassessments because it was a conservative approach and assumed that the linearresponse would overestimate pollutant uptake by plants EPArsquos assertion thatmetals bind to biosolids and are thus less available for plant uptake should bevalidated using the latest direct molecular scale techniques That assumptiondoes not consider the extent to which the proposed binding is reversible (Bell etal 1991) If soil conditions and land use change such as the soil acidifyingwhen organic matter decays uptake could increase (Heckman et al 1987Mulchi et al 1987ab Bell et al 1988 Adamu et al 1989 Chaney
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 191
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1990) although this was not the case for cadmium uptake by lettuce after 13ndash15 years in one experiment (Brown et al 1998) Other researchers believe thatthe plateau effect could be due to plant physiological factors rather thanattenuation due to biosolids chemistry (Hamon et al 1999) If that is the casethe conservatism of the linear assumption will depend on the metalconcentration at the plateau as compared with the concentration used in thebiosolids standards For example Sloan et al (1997) show some evidence ofcurve linearity in uptake of cadmium by lettuce above about 8 mgkg ofcadmium in soil
EPA pointed out that the linear approach underestimates the UC at lowconcentrations As the metal concentrations in biosolids have been reduced andresult in low-end concentrations in soil EPArsquos approach may underestimateuptake Thus any further risk assessment should focus on plant uptake over thelikely loading rates and range of soil concentrations resulting from biosolidsapplications in practice In addition other explanations for a plateau effectshould be investigated For example higher rates of biosolids application mighthave other effects such as increasing soil pH or enhancing plant growth whichresults in the ldquogrowth dilutionrdquo effect on metal concentrations
Many studies on plant uptake of metals have been published since the riskassessments were conducted for the Part 503 rule Some of the most relevantstudies to review are those of Sauerbeck and Luumlbben (1991) McGrath et al(2000) Chang et al (1997) Logan et al (1997) Sloan et al (1997) Brown etal (1996 1998) and Chaudri et al (2001)
Older data on trace elements in soils and plants must be carefullyevaluated as most of those data were derived using analytical methods that hadhigher detection limits than those that are characteristic of methods used todayError in crop analyses of low-concentration cadmium mercury and lead is welldocumented (Tahvonen 1996) Those errors may be associated with the highvalues observed in crops grown on some control plots used for UC calculationsin the EPA database Erroneously high values for controls have the effect ofdecreasing the slope of the UC Real UCs may be higher if accuratemeasurements on control plots are used (McBride 1998)
Finally the observed concentration in plant materials used as foodincluding both above-and below-ground produce is assumed in the abovestudies to be derived from actual uptake into the tissues However dust and soilparticles can be deposited on plant surfaces by wind harvesting and soilldquosplashrdquo after rain In the case of metals especially those that are relativelyinsoluble in soil these particles may become included in the plant tissue (Preeret al 1984) This ldquoentrapmentrdquo can be a substantial proportion of theconcentration of leafy or root vegetables (eg up to 5 of dry weight of leafygreens may be soil particles) (Cary et al 1994) Although these particles maynot be
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 192
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strictly taken up into the tissues they strongly adhere and are not efficientlywashed off during food preparation Consequently the metals in soil embeddedin plant tissue will be included in estimated plant metal concentrations
Exposure to Plants In the database used by EPA (1992ab) to deriveUCs some experiments have concentrations measured in the topsoil of eachexperimental rate whereas others were not measured and only the loading ofmetal added to the soil was recorded EPA used metal loading rates to calculateplant uptake of metals for all studies necessitating conversion to loadings forthose with concentrations given by multiplying the concentration by the weightof topsoil The studies that gave loading rates rather than soil concentrationshave several problems associated with their use First loading assumes that allthe metals remain on the plot for the duration of the experiment Thatassumption ignores two factors leaching losses (McBride et al 1997 1999Barbarick et al 1998 Richards et al 1998) and physical movement of soillaterally due to cultivation Both factors have the effect of decreasing the actualconcentrations of metals that plants are exposed to and make the plant uptakeslopes less steep Only those studies in the database for which actual soilconcentrations were recorded avoid this underestimation Second in the mainlyshort-term experiments that constitute the majority of the evidence plant rootsrespond to the concentration of metals in their environment and not to loadingrates That factor is important for assessing exposure For example in the short-term studies typical of the experiments used for the risk assessment if biosolidswere surface applied and not incorporated into the soil the roots might not havebeen exposed to the full metal concentration Alternatively if the biosolids wereploughed deeper than the assumed 15 cm crop roots would be exposed to asmaller concentration than anticipated
Soil concentrations of metals are therefore better estimates of exposure toplants than loading rates However several additional factors must be taken intoconsideration when using soil concentrations or loadings The rate at whichmetal concentrations in experimental field plots decrease due to cultivation anddispersion is proportional to the plot size the repetition of application thenumber of cultivations and the amount of control soil surrounding each plotand the difference in concentration (Sibbesen and Andersen 1985 Sibbesen etal 1985 Sibbesen 1986 McGrath and Lane 1989 Berti and Jacobs 1998 Sloanet al 1998) If a metal is added once or only on a few occasions theconcentration within the original treated area declines particularly rapidly withincreasing number of cultivations on small experimental plots (McGrath andLane 1989 Berti and Jacobs 1998) Decreasing metal concentrations in soilshave the effect of making the dose-response curve for plant uptake steeper asillustrated in Figure 5ndash6 The data in Table 5ndash7 show
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 193
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FIGURE 5ndash6 Effect of dilution of soil zinc concentration by cultivation Datafrom Table 5ndash7
that 5050 mixing of a biosolids-treated soil results in a plant uptake slopethat is twice that when cultivation effects are ignored
Another effect of mixing due to cultivation is the increase in metalconcentrations in nearby control plots That effect might be another explanationfor the unusually high concentrations of metals in plants from some of thecontrol treatments in the database Lack of proper controls may have madesome of the reported UC curves shallower and underestimated the real UCvalues (McBride 1998) This may not be as important in the few experimentsthat used large treatment plots (eg 30times73 meter plots used by Sloan et al[1998])
Calculations Two basic methods were used for calculating plant uptakeslopes
1 For studies in which one metal application rate and one plant tissueconcentration were given the following algorithm was used
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 194
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TABLE 5ndash7 Effect of Soil Mixing on Actual Soil Concentrations Due to Cultivationof Field Experimental Plots
Biosolids rate 1 Biosolids rate 2Metal in plant (mgkg of dry weight) 44 56Soil (mgkg) calculated from the loadinga 75 300Soil (mgkg) actualb 575 170
aLoadings 150 and 600 kgha both divided by 2 to account for mixing to 15 cm in soil of 133density (EPA 1992a) UC=12(300`75)=005bLoadings assumed to be 5050 mixed with surrounding control soil with 40 mgkg backgroundconcentration so actual concentrations (75+40)2=575 and (300+ 40)2=170 UC=12(170`575)=011
2 For studies in which multiple application rates and tissueconcentrations were given the slope was determined by least-squares linear regression
The first method is not an accurate method of measuring an uptake slopeas a full response curve is not used The second method also has problems Forexample using data on cadmium in spinach EPA fitted a linear function forfive data points The ldquobest-fitrdquo line for those data points resulted in an interceptfor cadmium at nearly 10 mgkg in spinach The control (no biosolids added)was in fact only 5 mgkg The effect of that difference is to make the UC slope040 (less steep than if the four data points had been treated separately in thesame way as the single-point UC calculations) resulting in UCs of 175 175075 and 045
EPA grouped crop species into seven categories and used the geometricmean of all available UC data on metals from field experiments for each ofthose crop groups There are a number of reasons why the geometric mean maynot be the appropriate statistic to use to represent these data In many cases anarithmetic mean will best approximate exposure for use in risk assessment EPAshould reexamine the statistic used to represent the UC after considering therisk assessment goals (ie identifying a reasonable maximum exposure [RME])and the causes of variation in the data set The number of data points used byEPA to determine the geometric mean UC value varies significantly for eachpollutant with only four points available for arsenic and 167 available forcadmium Data included a range of study conditions including varied pHObviously if the data set is very small the causes of variation will be difficultto elucidate However for the large data sets such as the one for cadmium amore sophisticated evaluation of the causes of variation should
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 195
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be possible and should be used to derive the most appropriate statistic for therisk assessment
Within a category such as leafy vegetables results were not weightedaccording to the fraction of diet Thus for example cadmium uptake into leafyvegetables constitutes a major component of the potential dietary dose ofcadmium Data on crucifers compose a high proportion of the available data yetmost diets contain a lower fraction of crucifers than lettuce The UC forcadmium into crucifers is generally much lower than the UC for lettuce Thustaking the geometric mean of available data gives greater weight to the lower-UC crucifers than lettuce Weighting the UCs by the fraction of diet would givea more representative UC for dietary exposures
Environmental and Crop Considerations A variety of environmentalfactors affect contaminant bioavailability including soil organic matterbuffering capacity oxide content pH temperature and rainfall In additiondifferent crops and even different cultivars of the same crop type vary greatly intheir tendency to take up pollutants from the soil That variation highlights theimportance of considering regional variations in environmental conditions andcrop types when assessing plant uptake assumptions for national applications
EPA recognized that soil pH has a significant influence the uptake ofmetal cations generally being higher at lower pH and the uptake of such anionsas arsenate and molybdate being higher at higher pH EPA also indicated thatthe data set considered included studies with pH as low as 45 However pHdifferences between untreated controls and biosolids-treated plots might also beanother contributory reason for the apparent plateau effect in the relationshipbetween loading and crop uptake Compared with control soil pH biosolids soilpH frequently increases after initial application of biosolids especially whenlime is part of the treatment process However that effect does not persist andpH can fall by 1ndash15 units because of leaching of cations and the mineralizationof the added organic matter (Chaney et al 1977) In the database the durationof many of the experiments is restricted to a few years after biosolids areapplied and that might also underestimate the UC slopes for many metals
EPA stated that agricultural biosolids-applied soils rarely have a pH below55 That is true but taking the median calculated UC from the data collectedtends to have the effect of biasing the effective UC to the near-neutral pH range(Stern 1993) Because the risk assessment does not take into account pH andinstead sets allowable loading for all soils this approach relies on the practiceof maintaining pH at near neutral values for crop production reasons
Cadmium zinc and chloride in soil have important effects on crop uptakeand consequences for human or animal nutrition (Chaney et al 1998 Reevesand Chaney 2001) Zinc in soil has a competitive effect on cadmium uptake
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 196
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by crops thus reducing cadmium uptake whereas chloride ions (present insaline soils or derived from irrigation water) preferentially increase cadmiummobility and crop uptake compared with zinc (McLaughlin et al 1994 Chaneyet al 1998) In earlier experiments that were used in the original risk assessmentdatabase zinc was of course present when cadmium uptake was studied
Livestock Concentrations
EPA used assumptions about transfer of pollutants from biosolids tolivestock and resulting human exposures to contaminants in meat organ meatpoultry dairy products and eggs in its screening process for identifyingpollutants to regulate and in its risk assessments for Pathways 4 and 5 (humanconsumption of animal products affected by chemicals taken up into foragefrom biosolids or by direct ingestion of biosolids) It is not clear why these twopathways were not combined to estimate chemical concentrations in livestockbecause of both soil ingestion and plant ingestion A much more appropriateintegrated approach was used by EPA in the revised risk assessment for dioxinsin biosolids (EPA 2001a) and in the dioxin reassessment (EPA 2000b) Thisapproach developed by Fries and Paustenbach (1990) involves the predictionof chemical concentrations in livestock based on the proportions of soil grassand feed in dry-matter intake
In the initial screening process to select contaminants for detailed riskassessment biosolids intake by livestock was assumed to be 5 of diet(presumably dry matter) even though intake could be 10 from a combinationof adherence to forage crops and direct ingestion of treated soil (EPA 1985) Inthe pathway-specific risk assessments used to develop the Part 503 rule EPA(1992a) assumed that 15 of a grazing animalrsquos diet is biosolids That valuewas based on the assumption that biosolids are applied to pasture once every 3years and that biosolids intake is 25 of diet in the year of application and 1in the other 2 years
Assumptions about pollutant intake due to biosolids should be based onestimated pollutant concentrations in soil pollutant uptake into crops soilintake by livestock and the relative bioavailability of the pollutant in soilrelative to the bioavailability in forage The proportion of biosolids in ingestedsoil is variable depending on the type and form of biosolids applicationclimate grazing habits percent of time spent in pasture percent of diet obtainedfrom pasture season and management conditions Soil ingestion by cattlefeeding on pasture can range from 1 to 18 of the diet depending on thegrowing season and climate (Fries 1995) and sheep might ingest as much as30 depending on the seasonal supply of grass and grazing management
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 197
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(Thornton and Abrahams 1983) On average soil is estimated to comprise about6 of the total dry matter intake of most grazing stock (Fries 1995 Wild et al1994) In risk-assessment documents EPA (1998 2000b 2001a) assumed thatsoil ingested by cattle averages 4 of diet dry matter and soil ingested by dairycattle averages 2ndash3 of diet because dairy cows spend less time in pasture Foruptake of pollutants from soil into animal tissue a relative bioavailability factoris needed to adjust for differences in the relative bioavailability of a chemical insoil as compared with that in forage In 1998 EPA suggested using a defaultassumption of 1 (no difference in bioavailability) in the absence of morespecific supporting data In risk assessments for dioxins (EPA 2000b 2001a)default values of less than 1 were used (eg 065 for the relative bioavailabilityof dioxins in soil to cattle) In the Part 503 rule risk assessment bioavailabilitywas calculated as the geometric mean of values obtained from researchliterature The appropriate statistic to use should be selected in the context ofcharacterizing RME exposures
In addition to direct ingestion of biosolids applied to soil biosolids sprayedonto forage adhere to plant surfaces It is important that pollutants in biosolidssprayed onto and adhering to crops be included in the forage chemicalconcentrations
Air Concentrations
Exposure to biosolids pollutants in air is considered in Pathway 11(airborne dusts) and Pathway 13 (volatilization from soil) Critical parametersthat influence air concentrations of pollutants such as wind velocity andtemperature should be reconsidered EPA (1992a) used a ldquotypicalrdquo windspeedof 45 ms in its risk assessments but data from the National Oceanic andAtmospheric Administration (NOAA 2000a) show that at 115 of 275 locationsin the United States for which long-term data are collected average annualwindspeeds exceed 45 ms For air temperature EPA used a national annualaverage of 15degC but average daily temperatures are higher than that forapproximately one-third of the United States (NOAA 2000b) The revised riskassessment for dioxins in biosolids (EPA 2001a) addressed regional differencesby relying on a database that divides the country into 41 distinct regions on thebasis of climate and other factors Meteorological data from each region wereused in the risk assessment to predict a distribution of annual average airconcentrations Whether average values are appropriate in assessing risks issubject to question however the use of regional data as part of a probabilisticassessment is a useful approach
Biosolids are generally spread during the growing season and not underwinter conditions Therefore warmer temperatures and higher rates of volatil
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 198
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ization would be expected at the time biosolids are applied This issue will beparticularly important in the valuation of short-term exposures For theseexposures risks posed under high-wind and high-temperature conditions shouldbe assessed
Surface-Water Concentrations
Calculations of the concentration of contaminants in surface water rest onseveral assumptions including watershed ratio contaminant load fromsediments and dilution EPArsquos risk assessment for Pathway 12 (human drinkingwater and ingesting fish from surface water contaminated by biosolids) assumedthat the biosolids-amended area is 1074 ha which is based on data from theNSSS (90th percentile for the size of agricultural areas used by publicly ownedtreatment works) The water body for which risks were assessed was assumedto have a watershed of 440300 ha (mean watershed size for the United States)an area greater than the size of Rhode Island and representing a fifth- to sixth-order stream Only 024 of the watershed is thus assumed to receive biosolidsEPA (1998) protocol suggested that the impacts on farm ponds be assessedbecause the farm family might be exposed through fishing and swimming Inthe EPA (2001a) reassessment of risks for dioxins in biosolids a much smallerthird-order stream was assumed and chemicals were assumed to enter thestream via wet and dry deposition from air and via runoff and erosion from thelocal (farm with agricultural fields and a buffer zone) and regional watershedsIt is not clear however what proportion of the watershed was assumed toreceive biosolids
In the original assessment of exposures from surface water EPA assumedthat the entire watershed is agricultural and that soil loss is the same throughoutthe watershed It is also assumed that all pollutants in the receiving stream arefrom biosolids and that no other pollutants enter the stream For a watershed aslarge as that postulated significant portions are likely to be forested areas thathave lower erosion rates than agricultural areas and other areas will be pavedincreasing storm runoff and erosion Thus a higher proportion of the sedimentin receiving water would be from agricultural areas including those amendedwith biosolids For a large watershed other sources of pollutants would beexpected
The Part 503 rule risk assessment used an average soil loss estimated fromagricultural lands of 85 metric tons (mt)ha-y This rate appears to be low asthe average annual soil loss has been measured to be 357plusmn564 kgsquaremeters and loss of 85 mtha-year was below the 50th percentile for measuredrates (Risse et al 1993) Sand was used as a worst-case soil type in the Part 503risk assessment Although sand would be a worst case for leaching it
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 199
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would not necessarily be that for erosion (Brady and Weil 1999) Also noconsideration was given to heavy rainfall events Many of these issues could beappropriately addressed by using a probabilistic surface-water model
In estimating the amount of pollutant available via surface water the totalconcentration in biosolids is reduced by estimating the fractions lost throughleaching volatilization and degradation (see earlier discussion of massbalance) The eroded material thus adjusted is assumed to be biosolids dilutedwith soil because of tilling into the top 15 cm of soil For surface applicationsuch as that on pastures or in conservation tillage scenarios that assumptionwould not be valid In the draft revaluation of dioxins in biosolids EPA (2001a)assumed that over time biosolids are mixed with the top 2 cm of soil inpastures however it is not clear whether or how this assumption wasincorporated into the runoff and erosion model
Groundwater Concentrations
Prediction of groundwater concentrations that might result from biosolidsapplication requires modeling and making assumptions about criticalparameters such as the partition coefficient leaching and dilution andattenuation Partition coefficients are used in the Part 503 rule risk assessmentto estimate the proportion of a contaminant that dissolves and is thus leachablePartition coefficient values for the regulated contaminants were taken from thework of Gerritse et al (1982) who studied only one type of biosolids andseveral soil types Recent studies suggest that processing methods for biosolidshave an influence on metal mobilities (Richards et al 1997 2000) as does pHand soil type A single partition coefficient based on a single type of aerobicallydigested biosolids and on a sandy loam soil of pH 8 was used for eachcontaminant in the risk assessment Some contaminants such as cadmiumshow much greater movement at lower pH and in sands Thus the partitioncoefficients used by EPA are not necessarily representative of the range ofconditions that exist in the United States
Leaching calculations are based on a model of contaminant movementthrough soil However there are several limitations of the model usedincluding failure to account for rapid transport through preferential flow pathsand for facilitated transport of contaminants in association with organicconstituents (McCarthy and Zachara 1989) For a number of inorganic andorganic contaminants evidence indicates that leaching might be greatestimmediately after application (Beck et al 1996 Richards et al 2000) Moreaccurate modeling is needed to estimate rates of leaching Soil-screeningguidance (EPA 1996b) pertaining to groundwater impacts from leachingsuggests a dilution
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 200
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and attenuation factor (DAF) of 1 or 20 in initial screening evaluations EPAnoted that those values can be used at sites with shallow water tables fracturedmedia or karst topography However in the Part 503 rule risk assessmentmuch higher dilution factors appear to have been used In the example given byEPA a DAF of 152 was used in evaluating arsenic in groundwater
Groundwater conditions vary greatly throughout the United States For thePart 503 rule to be applicable nationwide reasonable worst-case scenarios suchas areas with karst or gravel conditions need to be evaluated Groundwater wasnot evaluated in the reassessment of dioxins in biosolids (EPA 2001a) becausedioxins are unlikely to leach to groundwater to an appreciable degree howeverthe regional climate and soils database developed for that risk assessment couldbe adapted to support a more robust groundwater model
Human Intake Parameters
Assumptions regarding the intake behavior and characteristics of thehuman receptor should be updated using the most recent EPA (1997) guidanceon exposure factors (see Chapter 4 for more details) as well as newly publishedstudies One broad issue for both deterministic and probabilistic risk assessmentapplies to many of the intake parameters This issue is the reliability ofidentified distributions and upper percentile values for many intake parametersestimated from short-term studies with observations occurring over a period ofdays (EPA 1997) Upper percentiles identified in such studies are values forshort-term intakes only It is not appropriate to apply these values to representvariability in chronic intakes without assessing the potential for bias due toshort survey periods (Wallace et al 1994 Buck et al 1997) A number offactors contribute to overestimation bias in the upper percentiles of suchdistributions (Chaisson et al 1999) The various approaches proposed to correctthese biases (Wallace et al 1994 Buck et al 1997 Chaisson et al 1999) shouldbe considered prior to using biased distributions or upper percentile values inrisk assessments If the biases cannot be corrected use of extreme upperpercentile values should be avoided and the impact of the biases should beexamined in an uncertainty assessment This issue is an important considerationin assessing intakes of soil food and water The potential impacts are describedin greater detail below for soil ingestion The uncertainty and variabilityassociated with many of these parameters might be characterized by usingprobabilistic risk-assessment approaches (Stern 1993)
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 201
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Some important parameters and special considerations that should be givento biosolids exposures are duration of exposure bioavailability soil ingestiondietary intake of vegetables and animal products water consumption inhalationrate and body weight
Duration of Exposure Default assumptions about length of residence arebased on data on the amount of time people reside in one home Data on lengthof residence in one location vary among different populations Farm residentshave an average residence time nearly four times that of other households(Israeli and Nelson 1992) In performing a risk assessment pertaining to landapplication of biosolids the human receptor for many of the exposure pathwaysis a farm family member Residence times also vary regionally the northeasternregion having residence times nearly twice those in the western United States(Israeli and Nelson 1992)
Bioavailability The relative bioavailability of individual chemicals tohuman receptors can vary with exposure medium and should be accounted forin risk assessments if sufficient supporting data are available (EPA 1989) Soil-ingested chemicals typically are less bioavailable than soluble forms ofdrinking-water-ingested chemicals (NEPI 2000ab) Even for a given exposuremedium such as soil many factors can affect relative bioavailability includingthe characteristics of the biosolids matrix and the form of the contaminant (egmetal salt and organic complex) The contaminantrsquos form and relativebioavailability can change over time and with environmental conditions ThePart 503 rule risk assessment did not make adjustments to reflect differences inthe relative bioavailability of chemicals in different exposure media There is noEPA guidance regarding relative bioavailability but the default assumption istypically 10 The reassessment of dioxins in biosolids (EPA 2001a) is silent onthis issue
Soil Ingestion Incidental soil ingestion by children and adults is assumedto occur primarily from adherence of fine soil particles to hands or objects thatare subsequently placed in the mouth (EPA 1997) In the Part 503 rule riskassessment soil ingestion was considered only for children who were assumedto ingest 200 mgday of pure biosolids for 5 years It was calculated as the mostlimiting pathway for four of the regulated contaminants This pathway shouldbe revised to use estimated soil concentrations rather than biosolidsconcentrations and should use the same exposure duration as other exposurepathways Estimates of soil intakes should include intakes by teenagers andadults and particularly for home gardeners and farm family members whoseingestion of soil might be relatively high
The assumption that children ingest 200 mg of soil per day is consistentwith current EPA guidance that describes this value as a conservative estimateof the mean (EPA 1997) More recent studies suggest that this value might
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 202
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exceed a 95th percentile for long-term average daily exposure (Stanek andCalabrese 2000 Stanek et al 2001) Reported upper percentiles in soil-ingestion studies typically represent the upper percentiles among theobservations reported for all subjects during a short study period (eg among64 children observed for 7 days) Estimates of true average 95th percentile soilingestion over longer periods might be much lower (Table 5ndash8) It is criticalthat new more reliable information on the distributions of soil ingestion beconsidered in new risk assessments
Pica behavior for soil was considered in the screening process to selectchemicals for regulation but the child with pica was not used as a receptor inthe risk assessments There is no evidence that geophagia occurs routinely inchildren over long periods however many children might occasionally ingest1ndash10 g or more of soil (EPA 1997) This finding suggests that consideration ofpica behavior is most important when assessing acute exposures (EPA 1997)
The average amount of soil ingested by adults was estimated to be 10 mgday (Stanek et al 1997) EPA recommended that 50 mgday be used as aldquoreasonable central estimate of adult soil ingestionrdquo (EPA 1997) however theestimate was based on an earlier study by Calabrese et al (1990) and did notinclude this grouprsquos more recent analysis (Stanek et al 1997) Given the highdegree of uncertainty in soil-ingestion data EPA should make further researchon soil ingestion among children and adults a high priority Probabilisticassessments might also be useful for characterizing uncertainty and variabilityof this parameter
Dietary Intake of Vegetables The risk assessment of vegetable intakeevaluated risks based on an average nonmetropolitan diet around 1980 (USDA1982) A limitation of the 3-day food-consumption survey in this study is that 3days is insufficient to ascertain typical dietary intake (Anderson 1986) and islikely to overestimate long-term average upper-percentile intake Vegetableconsumption varies greatly and surveys suggest that vegetable intake has beenincreasing in the general population (EPA 1997) Biosolids exposure of thevegetarian home gardener would be a reasonable maximum exposure Dataused by EPA in its risk assessment for developing the biosolids standards showthat farm households on average consume 25 times more vegetables than thenonmetropolitan population (EPA 1997) Consumption also varies within aparticular population Unfortunately no data could be found that addressvegetarians who would be expected to have high rates of intake Considerationshould also be given to regional differences in production and assessment of thefraction of homegrown and nonhomegrown crops that are grown on biosolids-amended soils for the RME receptor
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 203
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TABLE 5ndash8 Estimates of True Average 95th Percentile Soil Ingestion for ChildrenOver Various Time Periods
95th Percentile Soil Ingestion Per Day (mg)Time (days) Anacondaa Amherstb
1 141 2107 133 17730 112 13590 108 127365 106 124
aStudy of 64 children aged 1ndash4 years residing in Anaconda MT mean soil ingestion =31 mgdaybStudy of 64 children aged 1ndash4 years residing in Amherst MA mean soil ingestion= 57 mgdaySource Data from Stanek and Calabrese 2000
Dietary Intake of Animal Products The risk assessment of animal-product intake (not including poultry or eggs) is based on an averagenonmetropolitan diet from around 1980 (USDA 1982) and is limited by itsshort-term surveys that do not adequately predict long-term average upper-percentile intake Consumption of animal products varies greatly An RMEreceptor would be represented by a livestock farm family consuming home-raised products (meat poultry and dairy) Data show that those householdsconsume far more animal products than the average nonmetropolitan consumerFarm resident mean meat intake is approximately four times that ofnonmetropolitan residents and mean dairy intake is approximately nine timesgreater for farm residents (EPA 1997) Consideration should be given to theassumptions made for the RME receptor about the fraction of the animalproducts coming from animals exposed to biosolids
Water Consumption Water-consumption rates should reflect more recentstudies and account for variations in expected activity and climate The studythat forms the basis for EPArsquos default water-ingestion rates was conducted over20 years ago Consequently the distribution of tap-water-ingestion rates used inthe model does not reflect expected reductions in tap-water ingestion because ofincreases in consumption of soft drinks and bottled water An analysis based ona 1994ndash1996 food consumption survey suggested as much as a 30 drop inmean tap-water consumption during the last two decades (EPA 2000c) Inaddition the tap-water-intake data reported by Ershow and Cantor (1989) werecollected for only a 3-day period therefore the extrapolation to chronic intakeis uncertain particularly for the upper percentiles (EPA 1997)
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 204
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Inhalation Rate Assumptions about inhalation rates should be based onthe specific RME receptor and likely activities by the receptor during exposureAssessment of acute exposures should reflect the higher inhalation rates thatmay be sustained for shorter periods whereas assessment of chronic exposuresshould reflect the variation in average population breathing rates over longerperiods Age-related variations in inhalation rate should also be part of theevaluation
DERIVATION OF RISK-BASED STANDARDS
The risk assessment conducted to support the Part 503 rule was designed tosupport the development of risk-based standardsmdashthat is to identifyconcentrations of specific chemicals in biosolids that could be applied to land inthe manner specified by the rule without posing unacceptable risks Four typesof standards were developed (1) cumulative pollutant loading rates (2) annualpollutant loading rates (3) pollutant concentration limits and (4) ceilingpollutant concentration limits A deterministic approach was used to calculatethe various standards (see Table 5ndash9) for the nine regulated metals EPAidentified an allowable dose for each chemical as a starting point and then usedpathway-specific algorithms that incorporate a number of exposure parameters(discussed previously in this chapter) to calculate the biosolids standards Theexposure pathway with the lowest pollutant limit was considered the ldquolimitingrdquopathway and this lowest value was used to establish the cumulative pollutantloading rates annual pollutant loading rates and pollutant concentration limitsThe ceiling concentration limits were set at either the 99th percentile levelfound in the NSSS or the risk-based number whichever was greater The majoraspects of the process are discussed below
Toxicity Assessment
The starting point of EPArsquos calculations was to identify a chemical dosethat is not expected to cause unacceptable adverse effects in humans For mostof the chemicals the starting point was an EPA-established measure of eithertoxicity (reference dose [RfD] or reference concentration [RfC]) orcarcinogenicity (cancer potency value [q1]) For two chemicals copper andzinc a recommended daily allowance (RDA) was the starting point This wasdone for copper because EPA has not established toxicity or carcinogenicityvalues for it An RfD is available for zinc but that value was consideredinsufficient to meet daily nutritional requirements so the higher RDA value
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 205
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TABLE 5ndash9 Pollutant Concentration Limits and Loading Rates for Land Applicationin the United States Dry Weight BasisContaminant Ceiling
ConcentrationLimit (mgkg)
CumulativePollutantLoadingRate Limit(kgha)
PollutantConcentrationLimit (mgkg)
AnnualPollutantLoadingRate (kgha-yr)
Arsenic 75 41 41 20Cadmium 85 39 39 19Copper 4300 1500 1500 75Lead 840 300 300 15Mercury 57 17 17 085Molybdenuma 75 mdash mdash mdashNickel 420 420 420 21Selenium 100 100 100 50Zinc 7500 2800 2800 140
aStandards for molybdenum were dropped from the original regulation Currently only a ceilingconcentration limit is available for molybdenum and a decision about establishing new pollutantlimits for this metal has not been madeSource 40 CFR Part 503
was used (EPA 1992a) None of the regulated contaminants were assessedas carcinogens
All the starting points are based on chronic exposure scenarios EPA riskassessments typically focus on chronic exposures because long-term exposureis generally a more sensitive end point than acute or short-term exposures (Theuse of chronic toxicity data will yield a lower or more protective standard) EPAperiodically reviews the literature and updates the dose-response assessmentsfor individual chemicals Thus any reassessment of risks associated with landapplication of biosolids should include verification that the most recent toxicityvalues are used Consideration should also be given to evaluating risks fromshort-term episodic exposures which may be important for volatile chemicals
Calculations
In deriving the risk-based standards a number of calculations andalgorithms were used to determine the concentration of a specific chemical thatcan be present in biosolids and not result in exceedance of the acceptable doseBecause EPArsquos acceptable doses include consideration of chemical
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 206
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ion
exposures to the evaluated inorganic contaminants from all sources the firststep was to determine the dose of the chemical from biosolids alone bysubtracting total background in take (TBI) of a chemical from the EPA-established acceptable dose The adjusted health parameter was then used inalgorithms specific to each exposure pathway The algorithms incorporatedpathway-specific information and assumptions regarding chemical intake suchas plant uptake of the pollutant to derive a pollutant limit In most casescalculation of the pollutant limit involved two or more algorithms
Target Risks
Selection of target risks is a policy decision made by EPA For carcinogensin biosolids EPA used a target incremental cancer risk of 1 in 10000 (1 times10`4)the high end of the 1times10`6 to 1times10`4 risk used by EPA in establishing variousregulations For noncancer health effects a hazard index of 1 (the ratio of thepredicted exposure either to the threshold dose for toxicity or to the predictedcancer risk) was used It was beyond the committeersquos charge to assess theadequacy of target risks used to derive risk-based standards however actualrisks might be substantially less than the target risks because in many cases theconcentrations of the regulated contaminants in biosolids are generally less thanthe regulatory limits
In developing the Part 503 rule EPA sought to develop one standard foreach chemical that would be protective in all circumstances that could bereasonably anticipated to occur Thus a standard derived for use nationwidemust provide adequate protection for all reasonably anticipated environmentalconditions biosolids types and application practices anywhere that biosolidsapplication might occur This goal necessitates assessing risks for exposureconditions that might occur anywhere in the United States
The Part 503 rule standards were derived to be protective for landapplication in accordance with the regulations Exposures that might occur dueto failure to comply with the regulations were not considered during thedevelopment of the biosolids standards An assessment of risks associated withnoncompliance is an enforcement issue and is not related to a determination ofthe adequacy of the methods used to derive risk-based standardsNoncompliance associated with risk assessment is thus beyond the scope of thisreport
INORGANIC CHEMICALS
In light of the advances made in risk-assessment methods discussed inChapter 4 and the need to update many of the exposure parameters used in
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 207
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t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
the risk assessment process the existing biosolids standards for inorganicchemicals clearly need to be reevaluated As noted in Chapter 2 averageconcentrations of some regulated inorganics in biosolids decreased substantiallythroughout the 1980s and early 1990s and have stabilized since that time (seeTables 2ndash23 and 2ndash24) Recent survey data from Pennsylvania that includes95th percentile values as well as median values suggest that in Pennsylvaniaand perhaps in other states pollutant limits will only rarely be exceeded formost inorganics (Table 5ndash10)
In order to assess the potential impacts of reevaluating the standards it isinstructive to compare the pollutant limits for biosolids with current risk-basedsoil screening levels (SSLs) for residential scenarios Such a comparison ispredicated on the assumption that inorganic chemical concentrations in soil towhich biosolids are added will never exceed the pollutant limits EPA (1995)has projected that at such time as the cumulative loading rate (kgha) has beenachieved the risk-based limit of acceptable soil concentration (mgkg) will alsohave been reached and would be 50 of the cumulative loading rate plus theinitial background concentration of the pollutant As can be seen fromTable 5ndash11 most of the pollutant limits are lower (ie more conservative) thanthe EPA residential SSLs based only on dermal and direct ingestion pathways
A limitation of such a comparison is that the residential SSLs are based onexposures via a limited number of exposure pathways including soil ingestiondermal contact with soil and inhalation of resuspended particulates The SSLsmay not be adequately protective for chemicals for which other exposurepathways may be especially important This limitation is of particular concernfor cadmium due to potential uptake into plants and for mercury due to thepotential for mercury entering surface water via runoff from soil to be convertedto methylmercury and bioaccumulated in aquatic organisms For this reasonTable 5ndash11 also shows risk-based screening levels developed by the British(UK Environment Agency 2002) that include consideration of home gardenexposure The importance of differing assumptions in assessing risk is pointedout by comparing the UK and EPA values (columns 2 and 3) which for someelements are significantly different The potential impact of including the plantuptake pathway on risk-based soil concentrations for some pollutants (egcadmium) is demonstrated by comparing the values in columns 3 and 4 ofTable 5ndash11
In addition to SSLs based on exposure pathways involving direct contactwith chemicals EPA has also devised soil SSLs for the protection ofgroundwater (EPA 2001b) A comparison of selected pollutant concentrationlimits
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 208
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TABLE 5ndash10 Median and 95th Percentile Trace Element Concentrations inPennsylvania Sewage Sludge Produced in 1996 and 1997 Compared with LimitsContained in the Part 503 RuleTrace Element Concentration in Sewage Sludge (mg
kg)Pollutant ConcentrationLimit (mgkg)
Median 95th PercentileArsenic 360 187 41a
Cadmium 226 739 39a
Chromium 351 314 1200bc
Copper 511 1382 1500c
Mercury 154 601 17a
Molybdenum 818 360 18bd
Nickel 226 845 420c
Lead 649 202 300a
Selenium 428 847 100a
Zinc 705 1985 2800c
aBased on risks for child eating biosolidsbThe current Part 503 rule does not include chromium and there is no cumulative pollutant loadinglimit or pollutant concentration limit for molybdenum The values given in this table were includedin the original Part 503 rulecBased on plant phytotoxicitydBased on animal eating feedSource Adapted from Stehouwer et al 2000
in biosolids with US background soil concentrations and soil screeninglevels for groundwater are presented in Table 5ndash12
A comparison of the biosolids pollutant limits with risk-based SSLssuggests that the pollutant standards are adequately protective for someexposure pathways (ie soilbiosolids ingestion) but may need to bereevaluated for others (ie ingestion of homegrown produce grown onbiosolids-amended soil) In this section two factors that are important forassessing human exposure to inorganic compounds and their toxicitymdashbioavailability to human receptors and metal speciationmdashare discussed Otherfactorsmdashplant uptake of metals and bioavailability of metals to plantsmdashwereaddressed earlier in the section on exposure parameters The general discussionis followed by a description of issues specific to several of the regulated metals
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 209
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TA
BL
E 5
ndash11
Pol
luta
nt C
once
ntra
tion
Lim
its
in S
ewag
e S
ludg
e C
ompa
red
wit
h R
isk-
Bas
ed S
oil C
once
ntra
tion
s (I
tali
c nu
mbe
rs r
epre
sent
ris
k-ba
sed
soil
conc
entr
atio
ns b
elow
the
Par
t 503
rul
e po
llut
ant c
once
ntra
tion
lim
its
)T
race
Ele
men
tP
art 5
03 P
ollu
tant
Con
cent
rati
on L
imita
(mg
kgD
W)
EP
A R
esid
enti
al S
SL
s(i
nges
tion
and
der
mal
) (m
gkg
DW
)
UK
Res
iden
tial S
GV
s(i
nges
tion
) w
itho
ut p
lant
upta
keb
(mg
kg D
W)
UK
Res
iden
tial S
GV
s(i
nges
tion
) w
ith
plan
tup
take
c (m
gkg
DW
)A
rsen
ic41
04
(40)
d20
20C
adm
ium
3970
301
(pH
6)
2 (p
H 7
)8
(pH
8)
Chr
omiu
mN
Ae
230
120
000f
200g
130g
Lea
d30
040
045
045
0M
ercu
ry17
231
0h15
8N
icke
l42
01
600
7550
Sel
eniu
m10
039
026
035
a Pol
luta
nt c
once
ntra
tion
lim
its
for
bios
olid
s ba
sed
on h
uman
hea
lth
risk
s e
xcep
t for
nic
kel (
plan
t phy
toto
xici
ty)
b Hou
se o
r ap
artm
ent w
ith
no p
riva
te g
arde
n ar
ea
c Hou
se w
ith
a ga
rden
wit
h th
e po
ssib
ilit
y of
inge
stio
n of
hom
egro
wn
vege
tabl
es
d Ars
enic
SSL
is 0
4 m
gkg
bas
ed o
n a
1 in
10
000
00 c
ance
r ri
sk V
alue
of
40 in
par
enth
eses
ref
lect
s th
e ca
ncer
ris
k of
1 in
10
000
used
for
the
Part
503
rul
ee C
hrom
ium
was
del
eted
fro
m th
e Pa
rt 5
03 r
ule
beca
use
of a
cou
rt s
uit
f Chr
omiu
m S
SL a
ssum
es th
at a
ll ch
rom
ium
is C
r(V
I) V
alue
for
Cr(
III)
is 1
200
00
g The
UK
SG
V f
or c
hrom
ium
ass
umes
that
all
chro
miu
m is
CR
(VI)
h M
ercu
ry S
SL is
bas
ed o
n th
e re
fere
nce
dose
for
mer
curi
c ch
lori
de S
SL f
or in
hala
tion
is 1
0 m
gkg
A
bbre
viat
ions
DW
dry
wei
ght
NA
not
app
lica
ble
SG
V s
oil g
uide
line
val
ue S
SL s
oil s
cree
ning
leve
l U
K U
nite
d K
ingd
om
Sour
ces
40
CFR
Par
t 503
EPA
200
1b U
K E
nvir
onm
ent A
genc
y 20
02
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 210
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
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not
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m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
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ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
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ting
how
ever
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not b
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tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
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ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
TA
BL
E 5
ndash12
Pol
luta
nt C
once
ntra
tion
Lim
its
in B
ioso
lids
Com
pare
d w
ith
Bac
kgro
und
Con
cent
rati
ons
and
Soi
l Scr
eeni
ng L
evel
s fo
r G
roun
dwat
er
Bac
kgro
und
Con
cent
rati
onsb
SS
L f
or G
roun
dwat
erc
Tra
ce E
lem
ents
Par
t 503
Pol
luta
ntC
once
ntra
tion
Lim
it (
mg
kg D
W)a
Ari
thm
etic
mea
n (m
gkg
)G
eom
etri
cm
ean
(mg
kg)
Geo
met
ric
stan
dard
devi
atio
n (m
gkg
)
Ran
ge (
mg
kg)
DA
F=
20 (
mg
kg)
DA
F=
1 (m
gkg
)
Ars
enic
417
25
22
23lt
01ndash
9729
1C
adm
ium
390
02ndash1
67d
017
52
70N
D-1
1d8
04
Chr
omiu
mN
Ae
5437
237
1ndash2
000
38f
2f
Lea
d30
019
161
86lt
10ndash7
00-g
-g
Mer
cury
170
090
058
252
lt0
01ndash4
62
01
Nic
kel
420
1913
231
lt5ndash
700
130
7S
elen
ium
100
039
026
246
lt0
1ndash4
35
03
a CFR
40
Part
503
Pol
luta
nt c
once
ntra
tion
lim
its
for
bios
olid
s ba
sed
on h
uman
hea
lth
risk
s e
xcep
t for
nic
kel (
plan
t phy
toto
xici
ty)
b Dat
a fo
r U
S s
oils
Sha
ckle
tte
et a
l 19
84
c EPA
200
1b
d Ran
ge o
f m
eans
rep
orte
d in
Dra
gun
and
Cha
isso
n (1
991)
for
var
ious
sta
tes
and
soil
type
s S
ingl
e U
S m
ean
not r
epor
ted
e Chr
omiu
m w
as d
elet
ed f
rom
the
Part
503
rul
e be
caus
e of
a c
ourt
sui
tf S
SL f
or to
tal C
r an
d C
r(V
I) T
his
path
way
is n
ot o
f co
ncer
n fo
r C
r(II
I)
g A s
cree
ning
leve
l of
400
mg
kg h
as b
een
set f
or le
ad
Abb
revi
atio
ns D
AF
dil
utio
n at
tenu
atio
n fa
ctor
NA
not
app
lica
b le
ND
not
det
ecte
d S
SL s
oil s
cree
ning
leve
l
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 211
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t th
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s ne
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igita
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ntat
ion
of t
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rigin
al w
ork
has
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ompo
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from
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the
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pese
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file
s P
age
brea
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re tr
ue to
the
orig
inal
lin
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ngth
s w
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brea
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s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
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tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
Bioavailability to Humans
The term ldquobioavailabilityrdquo may have different meanings in differentcontexts In the context of human exposures to chemicals in environmentalmedia bioavailability is the degree to which a chemical present in anenvironmental medium is capable of being absorbed into the systemiccirculation Bioavailability depends on the release of the chemical from themedium and the absorption efficiency of the released chemical Oral toxicityassessments of metals are often based on studies in which a metal salt isdissolved in water or mixed with food If the toxicity factors (reference dosesand cancer slope factors) used in risk assessments in soil or other heterogeneousexposure media are based on studies using soluble forms of the metals theimpacts of soil exposures could be overestimated
Reduced absorption of metals from biosolids-amended soils ingested byhuman receptors might be due to sorption and precipitation reactions of themetals with soil components such as metal oxides and humic substances anddue to the presence of metals in compounds with limited water solubility (Rubyet al 1999) For example it is well established that metals such as cobaltmanganese nickel and zinc can form metal hydroxide surface precipitates onmetal oxides clay minerals and soils The formation of these surfaceprecipitates significantly reduces the release of the metal even when strongacids and complexing organic ligands are used as dissolution agents(Scheidegger et al 1997 1998 Ford et al 1999 Scheckel et al 2000) Arseniclead mercury and nickel also occur in soils in compounds exhibiting a widerange of water solubility Thus metal dissolution from ingested soil could belimited during movement through the gastrointestinal tract Accordinglyabsorption will be reduced as the major mode of absorption of many metals ispassage of dissolved metal species across the small intestine epithelium(Whitehead et al 1996)
Risk-assessment guidance from EPA (1989) acknowledges the need tomake adjustments in exposure assessments to account for differences in relativebioavailability between the exposure medium in toxicity studies and theexposure medium in risk assessments These adjustments for reducedbioavailability of chemicals from such media as soils are typically termedrelative absorption factors (RAF) RAFs typically take the form of a fractionaladjustment in the exposure algorithms used to estimate intake or dose
In the Part 503 risk assessment EPA considered making such adjustmentsfor relative bioavailability (using the term rdquorelative effectivenessldquo) butconcluded that available data were inadequate to support default adjustments forthe metals being evaluated During the past decade substantial research bettercharacterizing the occurrence of reduced metal bioavailability in soils has been
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 212
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t th
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he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion
published (NEPI 2000a) Reduced metal bioavailability in biosolids-amendedsoils is very likely and several laboratories have active research programs onthe use of biosolids amendments as a method of reducing metal bioavailabilityin contaminated soils (Basta and Sloan 1999 Henry and Brown 1997)
Metal Speciation and Availability
The lack of direct information on the speciation of metals and metalloids inbiosolids and soil-biosolids mixtures complicates attempts to assess bothtoxicity and bioavailability of these chemicals Although a great deal ofinformation on metal contents of biosolids and soils exists the total content isnot indicative of the forms or species of the metals For several of the regulatedmetals toxicity varies with different forms of the metal and it is important todistinguish differences in the nature of toxicity from differences in solubilityand bioavailability of different metal forms
Mercury may be present in three forms with varying toxicity (ieelemental mercury inorganic mercury compounds and methylmercury) Theexposure routes of concern are different for the different mercury formsInhalation is the primary route of exposure to elemental mercury released fromsoil and ingestion is the exposure route of concern for inorganic andmethylmercury Consequently for evaluation in risk assessment the forms ofmercury in soil and other exposure media must be known or assumptions mustbe made regarding the forms present Arsenic compounds also exhibit markedvariation in toxicity The organic forms are practically nontoxic and inorganicforms are quite toxic Typically only inorganic arsenic compounds are assumedto be present in soil but for the reasons described below that assumption mightnot apply to biosolids In contrast the toxicity of inorganic cadmium and leadcompounds expected to be present in biosolids does not vary althoughsolubility and bioavailability can be highly variable
Most bioavailability studies of metals in soil have relied on animal speciesthat have anatomical and physiological characteristics different from humansOnly a few studies have assessed metal absorption from ingested soil byhumans The relative bioavailability of metals in soil is dependent on speciationof the metal size distribution of soil particles and composition of the soil
Chemical extractions (eg sequential extractions) can provide someinformation on the extraction ease such as readily exchangeable or occludedfrom various phases but the order of extractions and extractants that are usedcan create artifacts Such extractions also do not mimic dissolution rates likelyto occur in the human gastrointestinal tract Sequential extractions do notprovide direct speciation analyses For example many metals can exist as inor
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 213
Abou
t th
is P
DF
file
Thi
s ne
w d
igita
l rep
rese
ntat
ion
of t
he o
rigin
al w
ork
has
been
rec
ompo
sed
from
XM
L fil
es c
reat
ed f
rom
the
orig
inal
pap
er b
ook
not
fro
m t
heor
igin
al ty
pese
tting
file
s P
age
brea
ks a
re tr
ue to
the
orig
inal
lin
e le
ngth
s w
ord
brea
ks h
eadi
ng s
tyle
s a
nd o
ther
type
setti
ng-s
peci
fic fo
rmat
ting
how
ever
can
not b
ere
tain
ed a
nd s
ome
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted
Ple
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ganic and organic species and in multiple oxidation states and can be associatedwith multiple solid phases (eg metal oxides phyllosilicates and humicsubstances) Metals primarily form strong inner-sphere chemical bonds withmetal oxides clay minerals and humic substances that substantially restricttheir mobility in natural environments Moreover with time metals canundergo transformations with soils that often render them less prone toleaching In laboratory experiments such metals as nickel and zinc can formsurface precipitates on soils aluminum oxides and clay minerals that transformover time to more stable mixed metal hydroxide phyllosilicate phases Somefraction of the metals is sequestered even with treatment with acids and organicligands such as ethylenediaminetetraacetate (Scheidegger et al 1997 1998Ford et al 1999 Roberts et al 1999 Scheckel et al 2000 Scheckel and Sparks2001) Furthermore metal speciation and thus bioavailability is not static inthe natural environment Changes may result from weathering reactions andmicrobiological activity in soils (Hooda and Alloway 1994 Sadovnikova et al1996 Basta and Sloan 1999 Kamaludeen et al 2001)
The speciation of metals and metalloids in biosolids and biosolids-amended soils is critical in determining the mobility and bioavailability of thetoxic metals (Ruby et al 1999) In the last decade important advances haveoccurred in the use of in situ molecular-scale techniques that can provide directinformation on chemical speciation of metals and metalloids in model systemssuch as metal oxides and clay minerals and in soils One major innovation hasbeen the use of synchrotron-based spectroscopies such as x-ray absorption fine-structure spectroscopy (XAFS) to determine oxidative states and local chemicalenvironment of metals and metalloids at natural particle interfaces Thus metalspecies in heterogeneous materials can be determined in the presence of waterwithout having to dry the sample and subject it to desiccation Numerousstudies have appeared in the scientific literature on the application of XAFS andother in situ spectroscopic techniques to speciate metals in natural systemsRecent changes are the use of micro-focused XAFS and micro-x-rayfluorescence spectroscopy to speciate and map metal distributions in soils(Manceau et al 2000 Roberts 2001) With these techniques an area of squaremicrons can be chemically mapped and the chemical associations of variousmetals can be determined certain spots can be zoomed in on and via XAFSdata analyses the species of the metals at different locations can be determinedIn addition the quantitative associations of the metals with various componentsof the solid can be determined (eg metal oxides clays and humic substances)Scientists have applied micro-XAFS and micro-x-ray absorption near-edgestructure (XANES) to phosphorus and arsenic speciation in poultry-litter andpoultry-litter amended soils (Arai and Sparks 2001 Peak et al 2001) bothextremely heterogeneous
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materials Biosolids-applied soils will also be heterogeneous in regard to thedistribution of biosolids-borne metals Application of such techniques tobiosolids would allow for direct speciation of the metals and metalloids and abetter understanding of the mechanisms affecting bioavailability
Regulated Metals and Metalloids
The inorganic chemicals regulated on the basis of human health(specifically risks to children from direct ingestion of biosolids) are arseniccadmium lead mercury and selenium Specific issues to consider in updatingthe risk assessments for the first four of these metals are described below
Arsenic
The primary issue related to arsenic is EPArsquos treatment of arsenic in soil asnoncarcinogenic in the Part 503 rule risk assessment However ingestion ofinorganic arsenic in drinking water is an established cause of skin cancer andrecent studies strengthen the evidence that arsenic can also cause cancers of thelung and urinary bladder (NRC 1999 2001) In the Part 503 rule riskassessment EPA justified using the arsenic reference dose on the grounds thatthere was no evidence that soil arsenic is carcinogenic Although that assertionis true there is no evidence that arsenic absorbed into the body from ingestedsoil and arsenic absorbed from drinking water behave any differentlyConsequently current EPA risk-assessment practice is to treat inorganic arsenicin all media as potentially carcinogenic
However if arsenic is treated as a carcinogen it will be necessary toconfirm that it is present in biosolids as inorganic arsenic rather than organicforms that are much less toxic and noncarcinogenic As with many toxic metalsand metalloids the speciation of arsenic in biosolids is not well characterizedAlthough organic arsenicals are generally not present in soils in measurablequantities the extent of their presence in biosolids is not known Thus theforms of arsenic present in biosolids should be assessed and only the fractionthat is inorganic should be regulated
Total arsenic in soils has been reported to range from 01 to 97 ppm withan arithmetic mean concentration of 72 ppm and a geometic mean of 52 ppmfor surface soils in the United States (Shacklette and Boerngen 1984)Gustavsson et al (2001) reported that US soils have a mean arsenicconcentration of 557 ppm and 25th and 75th percentile concentrations of 421ppm and 706 ppm respectively Arsenic occurs in two major oxidative states
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arsenous acid (AsIII) and arsenic acid (AsV) AsIII is primarily present in anoxicenvironments and AsV is found in oxic soils Both arsenic species occurprimarily as oxyanions in the natural environment and strongly complex withmetal oxides such as aluminum and iron oxides as inner-sphere productsThese oxides and particularly manganese oxides can affect oxidation of AsIII
to AsV which reduces the toxicity of arsenic Arsenic can also occur as sulfideminerals such as arsenopyrite (FeAsS) and enargite (Cu3AsS4) at mining sites
There is reason to suspect that some of the arsenic in biosolids is in organicforms however no studies testing this hypothesis were found Ingestedinorganic arsenic is methylated and excreted primarily as monomethylarsonicacid (MMA) and dimethylarsinic acid (DMA) (NRC 2001) Farmer andJohnson (1990) examined the speciation of arsenic in urine excreted by workersexposed to inorganic arsenic compounds and found 1ndash6 AsV 11ndash14 AsIII14ndash18 MMA and 63ndash70 DMA Most dietary arsenic is organic arsenic andmany of these organic forms are excreted unchanged in the urine Thus mostarsenic from domestic sources in wastewater may be organic Under certainenvironmental conditions however organic arsenic has the potential tomineralize The possibility that biosolids-borne arsenic can be transformed fromorganic to inorganic forms should be evaluated The greater water solubility oforganic arsenic compounds makes it unlikely that these compounds willpreferentially segregate to biosolids and makes it difficult to predict thepredominant speciation of arsenic in biosolids
Studies of the relative bioavailability of soil arsenic have been limitedprimarily to soils from mining and smelting sites and from arsenic pesticidemanufacturing or application (NEPI 2000a Kelley et al 2002) Those studiesyielded relative bioavailability estimates of soil arsenic of 10 to 50 ascompared with bioavailability of soluble arsenic forms It might not be practicalto determine the relative bioavailability of arsenic in biosolids in animalexperiments because of the low arsenic concentrations typically present inbiosolids However in vitro approaches are available that may be used toestimate relative bioavailability of arsenic in biosolids Ruby et al (1999) notedthat the particle-size distribution and the chemical composition of the arsenicspecies greatly affect bioavailability Dissolution rates (and bioavailability)increase as particle size decreases In vivo and in vitro studies show that for aconstant particle size soil-arsenic phases such as arsenic sulfides and arsenicfound in slag have a lower bioavailability than iron manganese and lead-arsenic oxides (Ruby et al 1999) Bioavailability data also suggest thatbioavailable arsenic from soil occurs primarily from dissolution of surface-bound arsenic fractions or the exterior part of individual arsenic-containinggrains rather than from complete dissolution of discrete arsenic mineral phases(Ruby et al 1999)
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Cadmium
The most limiting exposure pathway for cadmium in the Part 503 rule riskassessment was exposure to a child from direct ingestion of biosolids To deriveconcentration limits for cadmium in biosolids EPA used the oral RfD andconsidered only a childhood exposure rate However the oral RfD is based on alifetime accumulation of cadmium in the kidney to the point where the toxicitythreshold which is associated with toxicity to the kidney cortex is reachedConsequently it is more appropriate to average child and adult exposure ratesover the course of a lifetime Children are expected to ingest greater quantitiesof soil per unit of body weight than adults but do so over a shorter period Thusa safe average daily dose will typically be an average of the child daily dose for6 years and an adult dose for 24 years or more
Conducting a multiplepathway risk assessment that aggregates exposuresfrom all pathways is particularly important for cadmium Because plants take upcadmium more efficiently than most other metals dietary cadmium is likely tobe an important exposure pathway in a revised risk assessment
A number of dietary factors are known to affect cadmium toxicity mostnotably dietary deficiencies in iron calcium and zinc may be associated withincreased cadmium body burden and toxicity (ATSDR 1999) There have alsobeen studies demonstrating a protective effect of zinc at overtly toxic doses ofcadmium (ATSDR 1999) More recent studies suggest that even when dietarycadmium intakes are only slightly increased increased zinc intake may limitincreases in cadmium body burden (Vahter et al 1996 Reeves and Chaney2001) Thus it may be useful to consider predicted dietary zinc intake whenevaluating predicted dietary intake of cadmium
Lead
The bioavailability of lead in biosolids-amended soils is an importantfactor in assessing lead exposures Absorption of lead in the gastrointestinaltract varies with age diet nutritional status and the chemical species andparticle size of lead that is ingested (Ruby et al 1999) Adults absorb 7ndash15 oflead ingested by dietary means and dietary absorption by infants and childrenranges from 40 to 53 (Ziegler et al 1978) In the Part 503 rule riskassessment EPA used a version of the integrated exposure uptake biokinetic(IEUBK) model to assess lead exposures of children EPA revised that model in1994 The Part 503 rule limit for lead was also set more restrictively than theIEUBK-based value for policy reasons
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The revised model includes a default assumption that children absorb 30of lead from soil as compared with 50 of lead from diet and drinking waterRecent reviews have summarized studies of soil lead from many kinds of sitesand show that soil lead bioavailability ranges from near zero to somewhathigher than the EPA default value of 30 (NEPI 2000a Ruby et al 1999) Thegreat variability in soil lead bioavailability reflects the great variation insolubility of different lead compounds For example soil lead from mine siteswith sulfidic ores exhibits low bioavailability and soil lead from mine siteswith carbonate ores exhibits much more bioavailability
Dissolution rate-controlling processes are important in determining orallead bioavailability because lead must dissolve in the gastrointestinal tract tobecome bioaccessible (Ruby et al 1992) Less-soluble lead minerals such aslead in calcium phosphates dissolve by surface-reaction controlled kineticsThe bioavailability of metals that dissolve via a transport-controlled mechanismis dependent on the mixing that occurs in the gastrointestinal tract anddissolution via surface-controlled phenomena is sensitive to transit times (Rubyet al 1999)
A number of studies have been conducted on the bioavailability of lead inbiosolids to livestock A study at the University of Maryland (1980) used 033 and 10 sewage-sludge compost in diet that had lead at 215 mgg of dryweight for 180 days No significant change occurred in the indicator tissue leadconcentrations despite the finding that fecal analyses show that the animalsingested greatly increased amounts of lead In similar studies Keinholz et al(1979) found that tissue lead was significantly increased by ingesting 12sewage sludge containing lead at 780 mgg These studies are suggestive of lowbioavailability but do not provide quantitative information that can be used in arisk assessment
Mercury
The speciation of mercury in land-applied biosolids is a critical factor inassessing its fate and transport EPA assumed that mercury in soil from landapplication of biosolids was similar in toxicity and bioavailability to mercuricchloride a highly water-soluble form of inorganic mercury Howevermethylmercury has been shown to be present in biosolids-amended soils(Cappon 1981 1984 Carpi et al 1997)
The formation of methylmercury is much greater in aquatic systems owingto biomagnification in aquatic food chains For this reason the potentialtransport from application sites to surface water is of greater concern formercury than for other metals Several studies have also reported emission of
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mercury vapors from biosolids Sunlight and heat can cause reduction of HgII toelemental mercury (Hg0) and volatilization from surface soils (Carpi andLindberg 1997 1998 Carpi et al 1997) That was observed when biosolidswere applied to a soil in which the vegetative cover had been removed and thebiosolids were incorporated in the soils to a small depth (Carpi and Lindberg1997 Carpi et al 1997) Methylmercury was also shown to be emitted to theatmosphere (Carpi et al 1997)
Other Regulated Inorganic Chemicals
Copper molybdenum nickel selenium and zinc are also regulated underthe Part 503 rule These metals are much less toxic when ingested as comparedwith the four metals described above suggesting that it is appropriate that theyare regulated on the basis of ecological or plant effects Standards for coppernickel and zinc were based on effects on plants the standard for selenium isbased on human health and the standard for molybdenum is a non-risk-basedceiling limit Nickel is the most toxic to humans when inhaled so it is importantthat inhalation of resuspended particulates be considered in any risk assessmentfor this metal
ORGANIC CHEMICALS
Biosolids are likely to include many categories of chemicals that differfrom the categories of chemicals of concern in industrial discharges Although itis impossible to identify all of these pollutants it is important that EPAcontinually think about the types of chemicals released into wastewaters andadded during wastewater and sewage-sludge treatment processes as part of itsprocess for updating the Part 503 rule Because some organic chemicals such asorganochlorines are persistent in the environment consideration should begiven to their tendency for trophic transfer and biomagnification which is alongstanding public-health concern (Svensson et al 1991) Particular attentionshould also be paid to chemicals that are lipophilic or that have lipophilicmetabolites or degradation products because those chemicals are more likely topartition to sewage sludge Consideration should also be given to toxic endpoints that might not have been evaluated adequately in the earlier assessment(eg potential interactions of chemicals with the endocrine system) (Colborn etal 1993 Safe 2000)
As discussed previously in the section Hazard Assessment and ChemicalSelection all organic chemicals considered by EPA were originally exempted
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from regulation In 1999 EPA proposed to add dioxins (a category ofcompounds that includes 29 specific congeners of polychlorinated dibenzo-p-dioxins polychlorinated dibenzofurans and coplanar polychlorinated biphenyls[PCBs]) to the regulation in response to its Round 2 assessment of additionalchemicals to regulate under the Part 503 rule No standard for dioxins has yetbeen finalized This section reviews some of the important considerations thatshould be given to dioxins and other organic chemicals and provides examplesof some of the types of chemical categories EPA should be assessing in thefuture
Environmental Fate and Transport
A variety of factors jointly determine which organic pollutants willpartition from wastewater to sewage sludge and how human receptors mightcome into contact with these chemicals in biosolids These factors includetreatment processes for wastewaters and sewage sludge the concentration of thepollutant in the wastewater and biosolids the method of biosolids applicationthe physicochemical properties of the chemical and environmental conditionsSome factors that are particularly important for organic pollutants are theirpersistence in the environment their potential for transport from soil to otherenvironmental media and their potential for uptake into plant and animal foods
Degradation rates vary among chemicals their half-lives ranging fromdays to years For individual chemicals degradation rates may also vary withenvironmental conditions and measures of persistence may be substantiallyaffected by the experimental design and analytical capabilities (Beck et al1996) It is also noteworthy that degradation of parent compound may not leadto loss of toxic potential if persistent toxic breakdown products are formed Thebreakdown of DDT (111-trichloro-22-bis(p-chlorophenyl)-ethane) to DDE(11-dichloro-22-bis(p-chlorophenyl)ethylene) and DDD (11-dichloro-22-bis(p-chlorophenyl)ethane) is an example of this phenomenon
Decreases in organic contaminant concentrations in biosolids-amendedsoils is usually not a linear function of time (Beck et al 1996) Chlorobenzeneconcentrations initially decline rapidly from biosolids-amended soil but about10 of the residues become recalcitrant and remain in soil up to 30 years afterapplication (Wang et al 1995) Reports of persistence of polyaromatichydrocarbons (PAHs) in biosolids-amended soil vary widely In a review of theavailable literature Beck et al (1996) found one study reporting a decline intotal soil PAHs of 80ndash100 20 years after biosolids application and anotherreporting 60 of benzo[a]pyrene (a persistent PAH) remaining 30 years after
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 220
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25 biosolids applications to a sandy loam soil In a study of biosolids-associateddi-(2-ethylhexyl)phthalate in a laboratory microcosm approximately halfremained after 1 year (Madsen et al 1999) A study of flocculent polymers usedas dewatering agents in wastewater treatment processes reported that thepolymer is partially degradable under both aerobic and anaerobic conditions(Chang et al 2001) however no data were available on the persistence of thesecompounds in environmental media
Half-lives for organic contaminants are also influenced by sewage sludge-treatment processes For example the half-life of linear alkylbenzene sulfonatescan be over a year under anaerobic conditions but they degrade with half-livesof 7ndash30 days under aerobic conditions (Cavalli and Valtorta 1999 Scott andJones 2000) Climatic conditions especially temperature and rainfall alsoinfluence degradation volatilization and leaching rates for organic chemicals inmixtures of biosolids and soil
Contaminants in biosolids are typically most available to plants andpotentially to animals immediately after application and before degradation mayhave reduced concentrations For both organic and inorganic contaminants inbiosolids the greatest potential for leaching which may also be related tobioavailability appears to occur immediately after application (Marcomini et al1988 Beck et al 1996) Sorption of organic contaminants from biosolids to soilparticles is another important determinant of mobility and availability Soilcomposition and moisture interact to influence sorption capacity for organiccontaminants (Chiou and Shoup 1985) In moist soils organic matter is thedominant constituent to which sorption occurs In dry soils where wateroccupies little of clay particle surfaces clay can absorb large amounts oforganic contaminants However the ability of a soil to sorb organiccontaminants generally increases with organic matter content Sorbed organiccontaminants may degrade by chemical biochemical or photochemicalreactions Desorption may occur from solid-to-solid solid-to-liquid or solid-to-gas phases
Mobilization into air may be an important route for transport of organiccontaminants to plants The rate of degradation and bioavailability of organiccontaminants in soils decreases with time (Alexander 2000) Sequestration intothe solid phase or nanopores of soil may explain this phenomenon Thissequestration should be considered when evaluating data on total chemicalconcentration in soil and may be addressed by studies of relative bioavailability
The relative importance of specific routes of exposure will vary with theorganic contaminant of concern climate and soil type For example volatilechemicals will be released from soil to air and hydrophobic persistent organicsare more likely to be retained in soil
EVALUATION OF EPArsquoS APPROACH TO SETTING CHEMICAL STANDARDS 221
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Dioxin and Dioxin-like Chemicals
The dioxins category includes seven chlorinated dibenzo-p-dioxins(CDDs) 10 chlorinated dibenzofurans (CDFs) and 12 coplanar PCB congenersThese compounds share common modes of toxic action and are considered agroup for risk assessment (Van den Berg et al 1998) Although the toxicity ofthese chemicals varies up to 5 orders of magnitude 2378-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent All the dioxins bind and activate the arylhydrocarbon receptor (AhR) The AhR is a ligand-activated transcription factorthat participates in regulating a battery of genes (Gu et al 2000) A change inexpression of AhR-regulated genes is the current explanation for much of thetoxicity of TCDD and dioxin-like compounds The CDDs CDFs and PCBs thatactivate the AhR are approximate stereoisomers of TCDD Because thestereoisomers of TCDD are all less potent than TCDD each is assigned apotency relative to TCDD for AhR activation (Van den Berg et al 1998) Theassigned potency is referred to as a toxic equivalency factor (TEF) Bydefinition the TEF for TCDD is 1 Multiplying the concentrations of eachCDD CDF or dioxin-like PCB in biosolids by their TEFs and summing theproducts yields the toxic equivalents (TEQs) in that material
EPA (1999a) has proposed application of TEQs in biosolids for settingregulatory standards The validity of this approach is supported by reviews ofrecent literature that consider tissue concentrations (Van den Berg et al 1998Gu et al 2000) There is at least one major limitation to application of the TEQconcept to estimating risks of dioxins in biosolids-amended soil Bioavailabilityof all CDDs CDFs and PCBs that contribute to TEQs is not equivalent (Jonesand Sewart 1997) A particular chlorination pattern distinguishes each of over400 potential CDD (75) CDF (135) and PCB (209) congeners Extent andpattern of chlorination markedly influences hydrophobicity and hence thetendency for sorption to and desorption from organic matter in a biosolids-amended soil Biodegradation rates water solubility (an inverse function ofhydrophobicity) and volatility generally decrease with an increase inchlorination for aromatic hydrocarbons Theoretically each CDD CDF andPCB congener processes a specific half-life and bioavailability in a biosolids-amended soil Complete characterization requires data on each congenerBecause of the impracticality of that requirement environmental chemistry datafor the most toxic congener (TCCD) typically provide the basis for riskassessment
EPA (1999a) has proposed a TEQ limit of 300 parts per trillion (ppt) inbiosolids applied to land which is well above the means of 32 or 48 pptdetected in recent biosolids surveys (Alvarado et al 2001 EPA 2002a) In the
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Alvarado survey 14 of 201 biosolids samples contained dioxin TEQs greaterthan 60 ppt Thirteen of those samples were in the range of 62ndash256 ppt and onesample contained dioxins at 3590 ppt The one unusually high dioxin level hasbeen verified by two laboratories the source of the dioxin has been identifiedthe sewage sludge is being land filled and investigation into the high dioxinlevel continues (RDominak AMSA Co-chair Biosolids ManagementCommittee personal communication with GKester Wisconsin Department ofNatural Resources May 24 2002)
Eljarrat et al (1997) reported that soil concentrations of CDDs CDFs anddioxin-like PCBs in biosolids-amended soil were 12 to 116 times greater thanthose in control soils one year after application of biosolids containing 56ndash260ppt TEQs Biosolids were applied in four consecutive years at rates thatexceeded the nitrogen-based Spanish annual application recommendations foragriculture (5ndash10 tonha) by 4- to 15-fold In soils with low initial TEQs (03ppt) concentrations remained suitable for agriculture In soil with high initialTEQs (31 ppt) concentrations increased to levels (86 picograms [pg]g TEQ)that would trigger German crop restrictions Molina et al (2000) concluded thatCDD and CDF concentrations in biosolids-amended soils are directly related toloading 1 year after application
Both atmospheric transport and biosolids application contribute to totalTEQ loading in agricultural soils (Jones and Sewart 1997) Atmosphericloading was more significant in urban sites than in rural sites The half-life ofCDDs and CDFs in soils is generally accepted to be about 10 years (Jones andSewart 1997) Therefore the history of contamination and atmospheric loadingin addition to biosolids application are worthy of consideration in siteevaluation For example assuming (1) biosolids with dioxins at 300 ppt (2) abiosolids application rate of 10000 kgha (3) biosolids incorporation into 15cm of soil (4) soil mass of 1200 kgm3 and (5) a dioxin half-life of 10 yearswith exponential decay rough estimates of dioxin concentrations are 165 ppt inagricultural soil after a single application and 1257 ppt after annualapplications for 10 consecutive years For biosolids containing dioxins at 50ppt the corresponding concentrations are 028 and 210 ppt
EPA (2001a) released a peer-review draft of a revised risk assessment fordioxins in biosolids that reflects responses to comments on the earlier riskassessment supporting the proposed TEQ limit of 300 ppt The revised riskassessment uses data from a recent biosolids survey and both deterministic andprobabilistic approaches to estimate dioxin concentrations in soil and otherexposure media near land-application sites Risks were evaluated for a farmfamily residing in an area receiving runoff from cropland and for a recreationalfisher For the farm family risk results were presented for specific pathways(soil ingestion air inhalation produce ingestion ingestion of poultry
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eggs beef and milk and breast-milk ingestion for an infant) and for totalmultiple-pathway risks Beef and milk ingestion were the primary contributorsto risks for both adults and children The risk results did not change whensurvey samples exceeding 300 ppt TEQ (the proposed standard) were excludedfrom the database because of low frequency of occurrence of increasedconcentrations A notice of data availability on EPArsquos revised risk assessmentwas released for public comment on June 12 2002 (EPA 2002a)
Other Organic Chemicals
Data regarding the occurrence of organic chemicals in biosolids is neededfor additional chemical categories and they should be given consideration infuture risk assessments Among these are flame retardants (eg brominateddiphenyl ethers) surfactants chlorinated paraffins nitro and polycyclic muskspharmaceuticals odorants and chemicals used to treat sewage sludge (egdewatering agents) Evaluation of these types of chemicals in risk assessmentwill depend on the characteristics of the compound their occurrence inbiosolids and the availability of toxicity data In this section brominateddiphenyl ethers are used as an example to illustrate a specific class of chemicalsidentified as a potential hazard in biosolids Other categories of compounds arereviewed briefly special consideration is given to pharmaceuticals and odorants
Brominated Diphenyl Ethers
Brominated diphenyl ethers (BDEs) are flame retardants used in thefurniture electrical and computer component and housing industries Onlypenta- octa- and deca-BDEs are of commercial interest (WHO 1994) Thecomposition and production estimates in 1994 for these BDEs are presented inTable 5ndash13 Environmental concerns about BDEs have arisen because theyhave been detected in various environmental media are highly persistent in theenvironment and bioaccumulate in aquatic food webs (de Boer et al 1998Hale et al 2001)
BDE formulations differ in their toxicological properties (WHO 1994)The acute toxicity of the deca- octa- and penta-BDEs is low There are noapparent adverse effects in rats fed deca-BDE at 50 gkg for 13 weeks Thatresponse is largely explained by very low absorption of deca-BDE across thegastrointestinal tract (about 03) There is evidence of toxic effects fromexposure to the less highly brominated BDE formulations For example rats
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TABLE 5ndash13 Composition and Approximate Annual Use of Brominated DiphenylEster FormulationsPreparation Composition Annual Worldwide Production (ton)Deca-BDE 97ndash98 deca-BDE
03ndash3 nona-BDE30000
Octa-BDE 43ndash44 hepta-BDE31ndash35 octa-BDE10ndash12 hexa-BDE9ndash11 nona-BDE0ndash1 deca-BDE
6000
Penta-BDE 50ndash62 penta-BDE24ndash38 tetra-BDE4ndash8 hexa-BDE0ndash1 tri-BDE
4000
Source Data from WHO 1994
fed a diet containing octa-BDE at 1 or 10 gkg for 13 weeks had reducedbody weight at both doses and decreased red-blood-cell count at the high doseAn increase in liver weight and no changes in body weight or blood-cell countswere found in rats fed a diet containing octa-BDE at 01 gkg for 13 weeks Ratsfed penta-BDE at 01 or 1 gkg for 4 weeks had increased liver weight without achange in body weight Histopathology analyses indicate that higher doses ofocta- and penta-BDE alter liver and thyroid tissue
More recent work focused on actions of BDEs on liver enzymes andthyroid hormones in rats Octa- and penta-BDE formulations increased theactivities of hepatic enzymes that metabolize thyroid hormone whereas deca-BDE did not (Zhou et al 2001) These increased enzyme activities wereassociated with reduced serum concentrations of thyroxin Because thyroid-stimulating hormone was not altered by BDEs increased elimination by theliver rather than decreased secretion by the thyroid appeared to explain thereduced serum thyroxin The potential for BDE metabolites to interact withtransthyretin (a protein that carries thyroxin in blood) was demonstrated byMeerts et al (2001) Three hydroxylated BDEs effectively displaced thyroxinfrom this protein Eriksson et al (2001) reported neurotoxic actions of a tetra-BDE and a penta-BDE congener in mice Neonatal exposure to both congenersaltered spontaneous behavior and the penta-BDE reduced memory
Despite the evidence of the toxic potential of BDEs a review of the abovestudies and other toxicological studies estimated that current human
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dietary intakes of BDEs were a million times lower than the lowest-observed-adverse-effect levels in animal studies (Darnerud et al 2001) Concentrations ofBDEs in human breast milk and fish have increased over time BDEconcentrations in breast milk from Swedish women have been reported toincrease exponentially over the past 25 years as commercial use of thesechemicals has increased (Hooper and McDonald 2000) Preliminary dataindicated that concentrations in milk from North American women were 10- to40-fold higher than those from Swedish women (Betts 2001) Noreacuten andMeironyteacute (2000) reported that BDEs in the breast milk of Swedish womenranged from 007 to 048 ngg of lipid between 1972 and 1980 and from 072 to401 ngg of lipid between 1984 and 1997
Few data are available on concentrations of BDEs in biosolids One studyreported that the sum of penta- and deca-brominated BDEs in biosolids rangedfrom 1 to 7 ppm in the United States (Hale et al 2001) The extent to whichBDEs in biosolids are related to current human body burdens is unclear
Surfactants
Surfactants used in laundry detergents and other cleaning products enterwastewater in large quantities from domestic and commercial wastewatersources Linear alkylbenzene sulfonates (LAS) alkyl phenol ethoxylates (APE)and alcohol ethoxylates (AE) are high-production surfactants that haverespective US annual consumptions of 415 322 and 208 million kg in 1990(McAvoy et al 1998) Standards for LAS and APE established in someEuropean countries are largely based on ecotoxicological impacts and nothuman health (Cavalli and Valtorta 1999) Use of nonylphenol-basedsurfactants is banned in Switzerland
Studies of LAS dominate the literature on degradation of surfactants Thetype of sewage-sludge treatment will have a strong impact on the presence ofsurfactants LAS for example is readily degraded in an aerobic environmentbut not in an anaerobic environment (Scott and Jones 2000) The half-life ofLAS in aerobic soils is 7ndash30 days (Cavalli and Valtorta 1999 Scott and Jones2000) and over a year under anaerobic conditions (Cavalli and Valtorta 1999)Soil concentrations of LAS immediately after biosolids applications range from05 to 664 ppm (Scott and Jones 2000) Differences in amounts of aerobic andanaerobic treatment before application might at least partially explain this widerange A 2-year feeding and reproduction study in rats with a LAS preparation(hydrocarbon-chain-length distribution of 10 to 14 carbons) revealed little or notoxicity (Buehler et al 1971) Rats fed LAS at a concentration of 5 gkg gainedbody weight and consumed food at the same
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