New Approaches to Adversity Assessment in

Food Safety Evaluation

Daniel Krewski, PhD, MHA

McLaughlin Centre for

Population Health Risk Assessment

University of Ottawa dkrewski@uottawa.ca; www.mclaughlincentre.ca

&

Risk Sciences International dkrewski@risksciences.com; www.risksciences.com

Declaration of Interest Statement

Scientific Director of the McLaughlin Centre for Population

Health Risk Assessment at the University of Ottawa,

supported by the R. Samuel McLaughlin Foundation

Natural Sciences and Engineering Research Council of

Canada Industrial Research Chair in Risk Science at the

University of Ottawa

Chief Risk Scientist at Risk Sciences International, a

Canadian company established in 2006 in partnership with

the University of Ottawa

Outline

• Traditional and Future Approaches

• Determining Adversity: Past and Future

• Severity Scoring Based on Degree of Adversity

• Evidence Integration

• Summary

Subchronic

Toxicity &

Reproduction

U

+

Accept

Reject

Defined

Test

Material

Exposure

Assessment

Acute

Toxicity

Reject

+ Genetic

Toxicology

-

Metabolism &

Pharmokinetics

+

Reject

-

Accept

S

Reject

+ -

?

Reject

Chronic

Toxicity

Accept

+

-

Traditional Approaches to Food Safety Assessment

Food Safety Council (1980)

Case Study: Sodium Saccharin

1981: Saccharin banned as a direct food additive on

the basis of urinary bladder tumours induced

in male rats in two-generation cancer bioassay

2010: Saccharin removed from US EPAs hazardous

substances list following re-evaluations of

the scientific data by the US NTP and by

the International Agency for Research on

Cancer in the 1990s

Two-Generation Lifetime Bioassay of Sodium Saccharin

Concentration Incidence of Percent

in Diet (%) Bladder Tumours Response

0.00 0/324 0

1.00 5/658 1

3.00 8/472 2

4.00 12/189 6

5.00 15/120 13

6.25 20/120 17

7.50 37/118 31

5.00 (through gestation) 0/122 0

5.00 (following gestation) 12/120 10

International Research and Development Corporation (1985)

Mechanism of Saccharin Induced Rat Bladder Tumours

National Toxicology Program Report on Carcinogens (1991), p. 91

“When sodium saccharin is fed to male rats at high dietary levels

(about 2.5%), the concentration of urinary sodium is increased and

the pH level is elevated (above 6.5). Under these conditions, binding

of saccharin and male rat α2u-globulin results in the formation of

silicon containing crystallized precipitate in the bladder

After binding, the precipitate enters the bladder urothelial walls and

is cytotoxic. Acting as microabrasives, the silicate and precipitate

particles irritate the mucosa and cause focal necrosis.

The loss of urothelial cells results in regenerative hyperplasia and

increased cell proliferation which, when sustained over a lifetime,

provides the basis for urinary bladder tumorigenesis.”

The Next Generation of Risk Science

• New paradigm for toxicity testing, as

described in Toxicity Testing in the 21st

Century (NRC, 2007)

• Advanced risk assessment

methodologies, including those

addressed in Science and Decisions (NRC, 2009)

• Population health approach,

incorporating multiple health

determinants and multiple interventions (Krewski et al., 2007, HERA, 13:1288-1312)

Krewski et al. (2014): http://ehp.niehs.nih.gov/1307260/

Toxicity Testing in the 21st Century

www.nas.edu

Future Approaches to Food Safety Assessment

Krewski et al. (2011), ARPH: 32:161-178.

Motivation for Change

Increased throughput, reduced costs

Early screening of potential new food chemicals

Test directly in human cells and human cell lines

Test directly at lower dose levels

Understand toxicity pathways and pathway

perturbations

Characterize interactions among toxicity pathways

Characterize interactions between test agent and

concomitant exposures

Compatibility of New Approaches with Existing Statutes?

“Agency rulemaking provides

the legal flexibility to

implement a new toxicity

testing program using existing

laws.”

The Environmental Forum (2008), pp. 46-51.

Implementing the New Paradigm: Selected Methodological Issues

1. Adversity

2. Dose-response

3. Variability

4. Susceptible populations

5. Dose and species extrapolation

6. Mixtures and multiple stressors

7. Uncertainty analysis

Determining Adversity: Past and Future

Issue Current

Approach

NexGen Approach

Adverse

outcomes

Apical outcomes in

mammalian systems,

or precursors to

these outcomes,

serve as the basis

for risk assessment.

In vitro assays identify

critical toxicity pathway

perturbations, which

serve as the basis for

risk assessment, even

in the absence of a

direct link with an apical

outcome.

Defining Adversity in the Absence of Apical Outcomes

Dose-Response Analysis: Signal-to-Noise Crossover Dose (SNCD)

Sand, Portier & Krewski, Environmental Health Perspectives (2011), pp. 1766-1774.

Application to High-Throughput Screening Data

Dose-response models fit to

over 10,000 datasets for over

1,400 chemicals tested as

part of the Tox21 program

44 nuclear receptor assays,

23 cytotoxicity assays, 12

stress response assays

Analysis used to calibrate

SNCD against traditional BMD

Exposure Science in the 21st Century

http://www.nap.edu/openbook.php?record_id=13507

Human Biomonitoring

National Health and Nutrition Examination Survey

Canadian Health Measures

Survey (CHMS)

NHANES

Establishing Biomonitoring Equivalents

Biomonitoring Equivalents

• 2,4-D

• Acrylamide

• Cadmium

• Cyfluthrin

• Di(2-ethylhexyl)phthalate

• Phthalate Esters: Diethyl phthalate Di-n-butyl phthalate Benzylbutyl phthalate

• Polychlorinated dibenzo-p-dioxins and dibenzofurans

• Toluene

• Trihalomethanes: Chloroform Dibromochloromethane Bromodichloromethane Bromoform

http://www.biomonitoringequivalents.net/html/chemical_specific_bes.html

High-Throughput Biomonitoring

Jones, D.P. (2016), Toxicol. Rep. 3, 29-45.

Combining High-Throughput In Vitro Testing with High-Throughput Exposure Assessment

Comparison of Bioactivity Patterns for 163 ToxCast Chemicals

with High-Throughput Exposure Modeling Results

Evidence Required for Establishing Dietary Reference Intakes

U-Shaped Dose-Response for Essential Nutrients

Dose (Concentration)

Essentiality

Excess Deficiency

Homeostasis

Zone

of

conflict

Zone

of

conflict

Very Low Very High

Resp

on

se

Highly

Abnormal

Normal

Resp

on

se

Highly

Abnormal

Normal

Joint Model for Excess and Deficiency (JMED)

Copper Toxicity Database: Severity Scoring of Adverse Events

Copper Toxicity Database

Optimal Intake of Copper

xMINDUE = 2.73 mg/day

For humans, a daily oral intake of 2.73 mg will minimize the probability of a departure

from a non-normal response attributed to excess or deficiency. The 95% confidence

interval for xMINDUE is (1.57, 4.46) and is analogous to an acceptable range of oral intakes.

Application to Manganese . . .

. . . with Incorporation of Pharmacokinetics

Evidence Integration

Review of EPA’s Integrated Risk Information System (NRC, 2014)

Systematic Review: Objective and Reproducible

Quantitative Synthesis Using Meta-Analysis

Summary

• New paradigm for toxicological assessment of chemicals based on:

− Toxicity Testing in the 21st Century (NRC, 2007)

− Exposure Science in the 21st Century (NRC, 2012)

− Using 21st Century Science to Improve Risk-Related Evaluations (NRC,

2017)

• Need for change motivated by

− Increased throughput and lower cost

− Greater human relevance

− Obtain evidence directly at human exposure levels

• New paradigm presents challenges in re-defining adversity, and

adaptation of regulatory practice to reflect new evidence of adversity

• New approaches to evidence integration and synthesis will ensure

consideration of all relevant data in food safety assessment

Further Reading

Barton-Maclaren, T., Darshan, S. and Mattison, D.R. [Eds]. Risk Science in the 21st Century.

International Journal of Risk Assessment and Management 20 (1/2/3):1-283.

Council of Canadian Academies (2012). Integrating Emerging Technologies into Chemical

Safety Assessment. Council of Canadian Academies, Ottawa.

I. Cote, M. E. Andersen, G. T. Ankley, et al. The next generation of risk assessment

multiyear study- highlights of findings, applications to risk assessment and future directions.

Environmental Health Perspectives DOI:10.1289/EHP233, 2016.

D. Krewski, M. Westphal, M. E. Andersen, G. M. Paoli, W. A. Chiu, M. Al-Zoughool, M. C.

Croteau, L. D. Burgoon, and I. Cote. A framework for the next generation of risk science.

Environmental Health Perspectives 122 (8):796-805, 2014.

National Research Council (2007). Toxicity Testing in the 21st Century: A Vision and a

Strategy. National Academy Press, Washington, D.C.

National Research Council (2012). Exposure Science in the 21st Century. National Academy

Press, Washington, D.C.

National Research Council (2014). Review of EPA's Integrated Risk Information System

(IRIS) Process. National Academy Press, Washington, D.C.

National Research Council (2017). Incorporating 21st Century Science into Risk-Related

Evaluations. National Academy Press, Washington, D.C.