Pesticide Risk Assessment Tribal Risk Issues

1. Pesticide Risk AssessmentTribal Risk Issues Michael S. Metzger USEPA

2. The Risk Assessment Paradigm: The ”Red Book” Hazard Identification Exposure Assessment Dose Response Assessment RiskCharacterization • From the National Research Council’s Risk Assessment in the Federal Government: Managing the Process, 1983. http://books.nap.edu/books/030904894X/html/1.html

3. Hazard Assessment: Standard Guideline Studies Acute Testing 6-Pack in orange – generally not used for risk assessment but for labeling

4. Hazard Assessment: Standard Guideline Studies Subchronic Testing:

5. Hazard Assessment: Standard Guideline Studies Chronic Testing Developmental Toxicity and Reproduction

6. Hazard Assessment: Standard Guideline Studies Mutagenicity Testing Special Testing

7. Dietary Exposure Assessment • Two components • Food and drinking water residues • Food and drinking water consumption -or- How much are you eating or drinking? How much pesticide is in it?

8. Drinking Water • Two sources: • Surface water: lakes, reservoirs, rivers • ground water: underground sources

9. Surface Water (SW) Sources of Drinking Water: Models • Used for most risk assessments • Input: phys/chem properties, environmental ½-lives • Tier 1: FQPA Index Reservoir Screening Tool (FIRST) • Provides high end values for EDWCs Surface Water Concentration Calculator (SWCC) • Tier 2: Pesticide Root Zone Model - Exposure Analysis Modeling System (PRZM-EXAMS) • Provides high end values for EDWCs • direct use in distributional and chronic assessments • Flooded field models (e.g., rice model)

10. Surface Water (SW) Sources of Drinking Water: Models Inputs to pay attention to: higher Kd = more soil binding = lower residues in water Kd : Soil/water partition coefficient (also called the distribution coefficient) Kd (L/kg) = Soil sorbed concentration (mg/kg) Dissolved concentration (mg/L) Aerobic soil metabolism Greater metabolism = lower residues Aerobic aquatic metabolism Lower PCA leads to lower residues Percent cropped area (PCA)

11. Ground Water Sources of Drinking Water: Models Models (SCIGROW and PRZM-GW) • Often used for risk assessment • Screening Concentration In GROund Water (SCIGROW) • Input: p-chem properties, environmental 1/2-lives, chemical-specific data • regression model • PRZM-GW • First principles model

12. Decrease in Risk Estimates with Risk Assessment Refinements Typical Degree of Refinement observed Exposure Hazard Standard approach With FQPA SF 1X Tolerance Field trial data 3X - 5X lower risk estimate Standard approach With FQPA SF Removed % crop treated used? Increasing refinement 100X - 1000X lower risk estimate Farm-gate monitoring data PBPK Modeling PDP data 10,000X - 100,000X lower risk estimate PDP Data A Risk assessment is not a number!

13. Residential Exposure Residential: non-job-related exposures • Handler: Mix, load, and apply by homeowner • Post-application: Reentry after application (e.g., playing on lawns, playing golf, rolling on rug, bystanders) • Dermal, inhalation, and oral routes

14. Data Summary We have the data we need for: • Toxicity • High end water residues • Food residues for registered uses on foods • Typical U.S. consumption Areas that would benefit from additional exposure data: • Non-standard exposures

15. Non-Standard Exposure Pathways

16. Challenges to Risk assessment for Non-Standard Scenarios • The number of potential site-specific chemical/exposure scenarios is large; site-specific exposure data is limited, e.g., • Game: To what extent are game animals (rabbits, deer, others) likely to be exposed to pesticides as a result of the chemical’s use patterns, and what levels would be expected in the meat from these animals? What is the typical consumption of each? • Fish: To what extent are specific water bodies contaminated with pesticides, and what are the resulting residues in fish tissue from various fish species? What is the typical consumption of each? • Other sources (e.g., straw): What other sources of pesticide exposure are possible based on the pesticide use patterns? • Scenario-Specific assessment • If specific chemical/exposure scenarios can be identified, approaches to address these might be achievable

17. What’s Covered by Current Risk Assessments, and What’s Not… • Or, where might we want to focus most attention

18. What Risks are Likely to be Covered by Current Assessments • Drinking water (or bathing water) • High end modeling inputs are used representing the highest exposure potential for both ground and surface water

19. What Risks are Likely to be Covered by Current Assessments • Processing, soil exposure, sediment exposure • Exposures should be minimal relative to other exposures, e.g., protecting for exposures to drinking water will also protect for these exposures which will be far lower

20. What Risks are Likely to be Covered by Current Assessments • Exposures from eating game animals • For chemicals with uses on animal feeds, bounding level estimates of residues are assumed in meat, milk, poultry, and eggs (MMPE) • While consumption values may be higher in some cases for game animals, this will usually be offset by the higher estimated residues in MMPE from farm-raised MMPE • Exceptions? • Possibly cases where highly lipophilic chemicals have uses which might result in residues in plants consumed primarily by game animals • Cases where residues aren’t found in MMPE, but are in some game animals due to long-range atmospheric transport, specific pesticide use patterns

21. What Risks are NOT Likely to be Covered by Current Assessments: Gathering Foods • If foods are gathered from areas where pesticides have been directly applied, such as roadsides and rights-of-way, there is potential for exposure • What data and information is needed? • Information on what pesticides are used in the area, how the pesticides are used, and what food commodities could potentially contain residues • If translation of available residue data is not possible for these foods, and screening level estimates show risks of concern, residue data may be required to refine the assessment.

22. What Risks are NOT Likely to be Covered by Current Assessments: Fish Consumption • Residues in fish vary widely depending on the properties of the pesticide, the water body the fish is taken from, the type and age of fish • What information is needed? • Information about pesticide use patterns and potential water contamination in the water bodies from which fish are taken • Information about the types of fish caught for consumption from the water bodies • Information about fish consumption patterns • If a screening assessment is not possible or leads to high risk estimates based on this information, chemical-specific fish residue data would be needed for refinement

23. What Risks are NOT Likely to be Covered by Current Assessments: Other Non-Standard Exposures • Other non-standard exposures • What information is needed? • Information about what other non-standard exposures are possible • Information about pesticide use which could lead to exposure • If a screening assessment is not possible based on this information, chemical-specific residue data would be needed for refinement

24. Discussion / Next Steps • How can we estimate consumption patterns for fish, game, and gathered foods which represent the range of potential consumption? • How can we determine pesticide residues in these commodities obtained from different locations? • Available monitoring data? • Models? • What other sources of exposure exists (e.g., from basket weaving), and how can we estimate potential exposures in these scenarios? • Other ideas?