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FIFRA SAP Meeting February 2, 2010

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Presentation on theme: "FIFRA SAP Meeting February 2, 2010"— Presentation transcript:

1 FIFRA SAP Meeting February 2, 2010
Draft Framework for Incorporation of Epidemiology and Human Incident Data into Risk Assessment Anna Lowit, Ph.D. Senior Scientist, Health Effects Division U.S. Environmental Protection Agency Office of Pesticide Programs

2 Outline of Presentations
Overview and Draft Framework for Incorporation of Epidemiology and Human Incident Data into Human Health Risk Assessment Retrospective and Ecologic Non-Cancer Epidemiology Studies: Atrazine Studies Case study A Prospective Epidemiology Studies: The Agricultural Health Study Case study B Human Incident Data-- Retrospective Case Study Using Diazinon Case study C

3 Organization of the Draft Framework
Reviewing Epidemiology Studies for Use in Pesticide Risk Assessment Types of studies Scientific factors to consider in reviewing Benefits & uses of epidemiology in risk assessment Human Incident Data Proposed Weight of the Evidence (WOE) Analysis On-Going Case Studies

4 Introduction Concepts in the Draft Framework are based on peer-reviewed, robust principles & tools Standard practice in epidemiology, toxicology & risk assessment Improvements based on recommendations from NRC 2007: Toxicity Testing in the 21st Century NRC 2009: Science & Decisions: Advancing Risk Assessment Flexibility to incorporate information from different sources Transparent tool for organizing, reviewing & interpreting complex information

5 How Do We Assess Risk? NAS 4-step paradigm Hazard Assessment
& Characterization Dose Response Assessment & Characterization Exposure Assessment & Characterization Risk Characterization 5

6 2007 NRC Toxicity Testing in the 21st Century
Dose Response Assessment Chemical Characterization Mode of Action Population Based Studies Compounds Dose Response Analysis for Perturbations of Toxicity Pathways Affected Pathway Assess Biological Perturbation Calibrating in vitro and human Dosimetry Exposure Guideline Measures of dose in vitro Metabolite(s) Human Exposure Data Hazard Characterization Exposure Assessment Risk Characterization Fig 3-7 Risk Assessment Components 6 6 6

7 FRAMEWORK FOR ECOLOGICAL RISK ASSESSMENT
Integrate Available Information Planning (Risk Assessor/ Risk Manager Dialogue) Source and Exposure Characteristics Ecosystem Potentially at Risk Ecological Effects PROBLEM FORMULATION Assessment Endpoints Conceptual Model 1. Management Goals 2. Management Options 3. Scope, Complexity, and Focus 4. Resources 5. Scheduling Analysis Plan As Necessary Acquire Data, Iterate Process, Monitor Results Characterization of Exposure Characterization of Ecological Effects Measures of Exposure Measures of Exposure Measures of Ecosystem And Receptor Characteristics Measures of Effect Measures of Effect ANALYSIS Exposure Analysis Ecological Response Analysis Exposure Profile Exposure Profile Stressor-Response Profile Stressor-Response Profile Risk Estimation RISK CHARACTERIZATION Risk Description Communicating Results to the Risk Manager Communicating Results to the Risk Manager Risk Management Risk Management

8 Draft Framework Proposes to use modified Bradford Hill Criteria in the Mode of Action Framework as the major tool for organizing, reviewing & interpreting data from many sources

9 Adverse Outcome Pathways
Source to Effects Pathway, Adapted from NRC, 2007 Structure Activity Relationships In vivo studies In vitro studies Pharmaco- kinetics Molecular Target Cellular Response Tissue/ Organ Chemicals Individual Population Biomonitoring data Toxicity Pathways Human Incidents Epidemiology Adverse Outcome Pathways Greater Toxicological Understanding Greater Risk Relevance 9

10 Mode of Action Framework
Promote maximal use of relevant information Focus species & dose-response extrapolations in mode of action context Basis for explicit consideration of confidence & certainty Improves transparency Harmonize across endpoints Tool for integrating data across many sources Including those from new technologies

11 Mode of Action Framework
Modified Bradford Hill Criteria Postulated mode of action Identify sequence of key events on the path to health outcome Experimental support Concordance of dose-response for key events Temporal relationships for key events Biological plausibility & coherence Strength, consistency & specificity Other modes of action Identify uncertainties Conclusion

12 Target tissue exposure to ultimate toxic species
EXTERNAL DOSE Target tissue exposure to ultimate toxic species Absorption, distribution, potential activation metabolic processes Biological perturbation(s) Pathological change(s) TOXICOLOGICAL EFFECT OF CONCERN Generic Set of Key Events in a MOA, Adapted from Boobis, et al (2009)

13 In vitro EXTERNAL DOSE Where can human information be used?
Target tissue exposure to ultimate toxic species Absorption, distribution, potential activation metabolic processes Biological perturbation(s) Pathological change(s) TOXICOLOGICAL EFFECT OF CONCERN Where can human information be used? In vitro

14 Deliberate dosing studies
EXTERNAL DOSE Target tissue exposure to ultimate toxic species Absorption, distribution, potential activation metabolic processes Biological perturbation(s) Pathological change(s) TOXICOLOGICAL EFFECT OF CONCERN Where can human information be used? Deliberate dosing studies

15 Biomonitoring EXTERNAL DOSE Where can human information be used?
Target tissue exposure to ultimate toxic species Absorption, distribution, potential activation metabolic processes Biological perturbation(s) Pathological change(s) TOXICOLOGICAL EFFECT OF CONCERN Where can human information be used? Biomonitoring

16 Epidemiology & Human Incidents
EXTERNAL DOSE Target tissue exposure to ultimate toxic species Absorption, distribution, potential activation metabolic processes Biological perturbation(s) Pathological change(s) TOXICOLOGICAL EFFECT OF CONCERN Where can human information be used? Epidemiology & Human Incidents

17 Draft Framework OPP has not yet completed a weight of the evidence analysis using epidemiology or human incident data OPP does have extensive experience applying the MOA Framework to animal data Example provided in the following slides Actual animal & in vitro data MOA has been peer-reviewed & used to assess cancer risk to a herbicide Hypothetical epidemiology data to show principles

18 Herbicide X: Sequence of Measurable Key Events in the Target Tissue
Active metabolite Urothelial Toxicity Urinary bladder from a female F344 rat treated with 100 ppm Herbicide X Sustained Regenerative Proliferation BrdU Labeling Other MoAs: DNA damage via ROS? Hyperplasia Urinary Bladder Tumors

19 Dose Response Concordance
Association of Key Precursor Events & Bladder Tumors in F344 Rats Temporal Dose (mg/kg bw/day) Active Metabolite in Urine Urothelial Toxicity Regenerative Proliferation Urothelial Hyperplasia Transitional Cell Carcinoma 0.2 (2 ppm) + (wk ± 0.01 uM) (wk 10-6/10, grade 3 or 4) - 1 (10 ppm) (wk ± 0.02 uM) (wk 3-2/7, grade 3) (wk- 10; 8/10, grade 3 or 4) slight (wk X inc) 4 (40 ppm) (wk ± 0.09 uM) (wk 3-7/7, grade 3) (wk 10-5/10, grade 3 or 4) (wk X inc) (wk 10- 4/10) 9.4 (100 ppm) (wk ± 0.15 uM) (6 hrs-6/7, grade 3) (24 hrs-4/7, grade 3 or 4) (wk 2 6/10, grade 5)(wk 10-0/10, grade 4 or 5) (wk X inc) (wk 2-3.9X inc) (wk X inc) (wk 8-7/10) (wk 10-9/10) (papilloma first obs at wk 107; carcinoma first obs at wk 87) Dose Response Concordance

20 Qualitative Concordance Quantitative Concordance
Key Event Qualitative Concordance Animals Humans Strength Quantitative Concordance Humans Presence of active metabolite in urine Yes, Data Metabolite present following exposure to analog; Direct exposure to herbicide X? Considerable In animals; but limited data in humans PBPK Model--based on use of dosimetry at the target tissue because it represents the rate-limiting event leading to proliferation Sustained urothelial cell damage and regenerative proliferation Unknown: Potential if sufficient metabolite and cytotoxicity is produced Considerable in animals, possible in humans but no data No data Bladder tumors Possible Considerable in animals; plausible in humans Limited evidence indicates significantly less metabolite produced 20 20

21 Additional In Vitro Data Available
Pharmacodynamics SAB suggested that the “EPA could assemble a case for toxicodynamic equivalency between the test species, rats, and humans from existing experimental data” Based on the results of in vitro studies, it is expected that at a similar dose at the target site (i.e. bladder urothelial) In vitro cytotoxicity to active metabolite in human and rat cells Microarray support Qualitatively the genes up-regulated in human urinary bladder epithelial (UROtsa) are similar to those up-regulated in rat urinary bladder epithelial cells (MYP3) exposed to Herbicide X in vitro. Rat cell line was quantitatively more sensitive compared to the human cell line. Humans and rats are expected to respond pharmacodynamically similar at the target site.

22 What if more human information were available for Herbicide X?

23 Herbicide X: Sequence of Measurable Key Events in the Target Tissue
Active metabolite Biomonitoring data Urothelial Toxicity Epidemiology data: qualitative or quantitative characterization Sustained Regenerative Proliferation Hyperplasia Urinary Bladder Tumors 23 23

24 ?? Temporal - Dose Response Concordance + slight 0.2 (2 ppm)
Dose (mg/kg bw/day) Active Metabolite in Urine Urothelial Toxicity Regenerative Proliferation Urothelial Hyperplasia Transitional Cell Carcinoma Human Epi 0.2 (2 ppm) + (wk ± 0.01 uM) (wk 10-6/10, grade 3 or 4) - ?? 1 (10 ppm) (wk ± 0.02 uM) (wk 3-2/7, grade 3) (wk- 10; 8/10, grade 3 or 4) slight (wk X inc) 4 (40 ppm) (wk ± 0.09 uM) (wk 3-7/7, grade 3) (wk 10-5/10, grade 3 or 4) (wk X inc) (wk 10- 4/10) 9.4 (100 ppm) (wk ± 0.15 uM) (6 hrs-6/7, grade 3) (24 hrs-4/7, grade 3 or 4) (wk 2 6/10, grade 5)(wk 10-0/10, grade 4 or 5) (wk X inc) (wk 2-3.9X inc) (wk X inc) (wk 8-7/10) (wk 10-9/10) (papilloma first obs at wk 107; carcinoma first obs at wk 87) Dose Response Concordance

25 Qualitative Concordance Quantitative Concordance
Key Event Qualitative Concordance Animals Humans Strength Quantitative Concordance Humans Presence of active metabolite in urine Yes, Data Metabolite present following exposure to analog; Direct exposure to herbicide X? Considerable In animals; but limited data in humans PBPK Model--based on use of dosimetry at the target tissue because it represents the rate-limiting event leading to proliferation Sustained urothelial cell damage and regenerative proliferation Unknown: Potential if sufficient metabolite and cytotoxicity is produced Considerable in animals, possible in humans but no data No data Bladder tumors Human Info Considerable in animals; plausible in humans Human info 25 25

26 Mode of Action Framework
Promote maximal use of relevant information Focus species & dose-response extrapolations in mode of action context Basis for explicit consideration of confidence & certainty Improves transparency Harmonize across endpoints Tool for integrating data across many sources Including those from new technologies 26 26

27 Mode of Action Framework
All scientific work is incomplete— whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us as a freedom to ignore the knowledge we already have or to postpone the action that it appears to demand at a given time (Hill 1965) 27 27

28 Organization of the Draft Framework
Reviewing Epidemiology Studies for Use in Pesticide Risk Assessment Types of studies Scientific factors to consider in reviewing Benefits & uses of epidemiology in risk assessment Human Incident Data Proposed Weight of the Evidence (WOE) Analysis On-Going Case Studies

29 Outline of Presentations
Overview and Draft Framework for Incorporation of Epidemiology and Human Incident Data into Human Health Risk Assessment Retrospective and Ecologic Non-Cancer Epidemiology Studies: Atrazine Studies Case study A Prospective Epidemiology Studies: The Agricultural Health Study Case study B Human Incident Data-- Retrospective Case Study Using Diazinon Case study C

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