oxide metal overview of antimony trioxide (ato) workplan risk assessment sharon oxendine office of...
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OxideMetal
Overview of Antimony Trioxide (ATO) Workplan Risk Assessment
Sharon OxendineOffice of Pollution Prevention and Toxics November 13, 2013
Antimony Trioxide (ATO)CASRN 1309-64-4
Presentation Overview
This presentation will provide: Background on ATO Key science issues
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Please comment on the clarity, strengths and weaknesses of the assessment and how it specifically may be improved.
Basis for Selection
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* Human Health Effects - inhalation toxicity - possible carcinogen
* Exposure - 23,000 metric tons imported in 2012 - widespread use in consumer products
* Environmental Releases - persistence
- bioaccumulation
Scope of the Assessment
Evaluated ecological risks associated with ATO use in halogenated flame retardants
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× Human health risks were not the focus of this assessment
ATO
Antimony Compounds
Conceptual Model for ATO Risk Assessmentfocuses on ecological risks resulting from
industrial releases to water
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Chemistry, Fate and Transport
Please comment on the use of chemistry, fate and transport information to evaluate bioavailability in environmental media.
Hazard Characterization
Please comment on the use of toxicity data for antimony trichloride to characterize aquatic toxicity.
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Criteria for Selection of TRI Facilities
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NAICS codes
Reported water releases
Availability of “7Q10” streamflow data
Monitoring: USGS-NWIS & EPA STORET
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Monitoring Data:
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Can we generalize from this data to other regions?
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Are there concerns or limitations in these data sets that may impact their utility for risk assessment?
Are there other major sources of environmental monitoring data (or other pertinent information) that EPA should consider in the exposure assessment? If so, please provide the necessary citations and/or data for inclusion in the revised document.
Please comment on the use of these data sets to characterize ecological exposures. Do they adequately reflect conditions at other locations in the US?
Use of the category ‘antimony compounds’ as a surrogate to estimate ATO releases
Are there other data sources and/or approaches that EPA should consider for estimating environmental releases? If so, please provide citations or data for consideration in further revision of the draft assessment.
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Exposure and Fate Assessment Screening Tool (Version 2) model estimates of surface water concentrations
Two release scenarios (assuming total yearly TRI releases occurred over a period of 24- or 250 days/year) were used to provide a range of predicted water concentrations for comparison with hazard benchmarks (concentrations of concern). Please comment on the EFAST2 modeling approach used to assess aquatic risks.
Risk Quotient Approach
RQ =Environmental Concentration
COC
Environmental concentrations reflect measured or estimated values
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COCs were calculated from the most sensitive effect levels
Risks indicated when the environmental concentration exceeds COC (i.e., RQ > 1)
Findings reported in this assessment are thought to represent conservative estimates of risk. Please comment on the validity of this statement and the likelihood that actual risks have been over (or under) estimated.
Please comment on the implicit assumption that antimony levels measured in environmental media reflect inputs from various types of antimony compounds and end use applications and how this could impact risk estimates.
Validity of Assumptions
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Risk Summary
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Media Type Organism Endpoint COC
MonitoringData
ModeledData
Water
C. viridissima 96-hour LC50 = 1.77 mg/L 354 ppb (acute) No exceedance One exceedance
P. Promelas 30-day GMATC = 1.62 mg/L 162 ppb (chronic) ~ 0.2% above chronic COC
No exceedances
Sediment L. variegatus or C. riparius 28-d NOEC = 112 mg Sb/kg dw
112 mg Sb/kg dw (acute) No exceedances -
11.2 mg Sb/kg dw (chronic)
~ 0.7% above chronic COC -
Monitoring Results
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Selected TRI facilities ( ) are shown as a point of reference
Conclusion
Minimal risks are expected for ecological organisms:
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Use of highly sensitive ecological species showed few instances where measured or predicted concentrations in environmental media exceeded the COC for water-, or sediment-dwelling organisms.
The available environmental monitoring data reflect input from various sources and types of antimony compounds.
Use of ‘antimony compounds’ as a surrogate for ATO and model estimates based on the assumption of yearly TRI releases occurring over a 24-day period provide conservative estimates of exposure potential.
Uncertainty and Data Limitations
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Risk findings are constrained by a number of uncertainties regarding data quality (e.g., adequacy of TRI reporting, model assumptions, and environmental monitoring data).
There is little or no overlap between the geographic locations of selected TRI facilities and the available monitoring data, therefore a direct linkage to ATO use as a flame retardant synergist is not possible.
Environmental fate and transport are influenced by site-specific conditions that can impact bioavailability. Since these parameters vary, it is difficult to extrapolate to other geographic regions within the US.
Key Technical Issues Raised in Public Comments
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• Hazard- Lack of transparency in hazard characterization- Unclear criteria for study selection
• Risk- Risk quotient versus margin of exposure - Use of phrases such as “minimal concern”
• Exposure- Use of conservative assumptions in exposure assessment- Rationale for selection of end-use scenario
Acknowledgements
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Kay Austin Jay Jon
Stanley Barone Sharon Oxendine
Cathy Fehrenbacher Wen-Hsiung Lee
Nhan Nguyen Tim Lehman
Louis Scarano Sara Pollack
Christina Cinalli Emma Lavoie
Rick Fehir Kirsten Hesla
Contract SupportPortions of this document were developed with support
from SRC, Eastern Research Group and Versar.
Thank you!
Test Organism Species Endpoint Antimony Compound Value Reference
Fish Pagrus major 96-hour LC50 SbCl3 6.9 mg Sb/L Takayanagi (2001)
Aquatic invertebrate Chlorohydra viridissima 96-hour LC50 SbCl3 1.77 mg Sb/L TAI (1990)
Aquatic plant Pseudo kirchneriella subcapitata
72-hour LC50
(growth rate)SbCl3 EC50 > 36.6 mg/L
NOEC = 2.11 mg Sb/LLOEC of 4.00 mg Sb/L
GMATC = 2.91 mg Sb/L
Heijerick and Vangheluwe (2004)
Aquatic plant P. subcapitata 72-hour LC50
(growth rate)Sb2O3 NOEC = 0.396 mg Sb/L
LOEC = 1.32 mg Sb/LGMATC = 0.723 mg Sb/L
LISEC (2001)
Fish Pimephales promelas 30-day (growth) SbCl3 NOEC = 1.13 mg Sb/LLOEC = 2.31 mg Sb/L
GMATC = 1.62 mg Sb/L
Kimball (1978)
Fish P. promelas 30-day (growth) Sb2O3 NOEC >0.0075mg /L LeBlanc and Dean (1984)
Aquatic invertebrate Daphnia magna 21-day (reproduction)
SbCl3 NOEC = 1.74 mg Sb/LLOEC = 3.13 mg Sb/L
GMATC = 2.33 mg Sb/L
Heijerick and Vangheluwe (2003b)a)
Aquatic Toxicity Data
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Sediment Toxicity Data
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Test Organism Species Endpoint AntimonyCompound Value Reference
Amphipod Hyalella azteca Survival/growth/reproduction
SbCl3 NOEC = 87 mg Sb/kg ww (124 mg Sb/kg dw)
Heijerick and Vangheluwe (2003a)
Oligochaete Lumbriculus variegatus
Survival/growth/reproduction
SbCl3 NOEC = 78 mg Sb/kg ww (112 mg Sb/kg dw)
Heijerick and Vangheluwe (2005a)
Midge larvae Chironomus riparius
Survival/growth/reproduction
SbCl3 NOEC = 78 mg Sb/kg ww (112 mg Sb/kg dw)
Heijerick and Vangheluwe (2005b)
Test Organism Species Endpoint Antimony Compound Value Reference
Springtail Folsomia candida Reproduction Sb2O3 NOECreproduction = 999 mg Sb/kg dwLOECreproduction=2,930 mg Sb/kg dw
Moser (2007)
Earthworm Eisenia fetida Adult survival/ juvenile production
Sb2(SO4)3 NOEC/LOEC adult survival = 617/697 mg Sb/kgNOEC/LOEC juvenile production = 60/86 mg Sb/kg
Simini et al. (2002)
Enchytraeid Enchytraeus crypticus
Adult survival/ juvenile production
Sb2(SO4)3 NOEC/LOEC adult survival = 384/538 mg Sb/kg NOEC/LOEC juvenile production = 100/140 mg Sb/kg
Kuperman et al. (2002)
Springtail F. candida Adult survival/ juvenile production
Sb2(SO4)3 NOEC/LOEC adult survival = 100/126 mg Sb/kgNOEC/LOEC juvenile production = 100 /126 mg/kg
Phillips et al. (2002)
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Soil Toxicity Data
U.S. Geological Survey Open-File Report
http://mrdata.usgs.gov/geochem/doc/home.htm
USGS National Stream Quality Accounting Network (1996-2000)
http://pubs.usgs.gov/wri/wri014255/results/detect/pd01095.png
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ANTIMONY STATISTICS1
(Metric tons of antimony content)
United States: 2008 2009 2010 2011 2012Mine production -- -- -- -- -- Smelter production: Primary W W W W W Secondary 3,180 3,020 3,520 3,230 3,730Exports:Metal, alloys, waste and scrap (gross weight) 366 385 427 581 847 Antimony oxide2 1,830 1,710 2,120 3,590 3,870 Imports for consumption 29,000 20,200 26,200 23,500 22,600 Reported industrial consumption, primary antimony 8,140 6,770 8,860 10,200 10200 Price, average3 (cents per pound) 279.5 235.6 401.2 650.3 564.5Global mine production 185,000r 154,000 178,000r 183,000r 174,000e e Estimated. r Revised. W Withheld to avoid disclosing company proprietary data, -- Zero.1Data are rounded to no more than three significant digits, except prices.2Antimony content data were calculated by the U.S. Geological Survey.3New York dealer price for 99.5% to 99.6% metal, cost, insurance, freight U.S. ports.
(USGS, 2012)