Human Health Risk Assessment and Management

1. Human Health Risk Assessment and Management

2. What is Risk Assessment • Scientific approach for evaluating potential for harm from hazardous substances and activities • How harmful? • How important a priority (comparative risk)? • How clean is clean?

4. Human Health Risk Assessment Data Collection and Evaluation Exposure Assessment Toxicity Assessment Risk Characterization

5. Data Collection and Evaluation • Identify concentrations of contaminants at site • Compare findings to naturally-occurring (background) levels near site • Ensure control samples are not tainted by site activity • Generally exclude low frequency detections (< 5%) in risk assessment

6. Exposure Assessment • Identify and estimate concentrations of chemicals potentially affecting humans • Characterize the site in terms of: • Physical characteristics • Soil characteristics, surface water location, groundwater (flow depth), meteorology • Exposed populations • Human activities (recreation, residential) • Proximity to release • Potential future uses

7. Identify exposure pathways • Determine amount of exposure for each pathway using monitoring data or fate and transport models • Analyze concentrations, frequency and duration of contaminant exposure to population groups • Consider characteristics of affected population groups - size of individuals, age, other factors

8. Toxicity Assessment • Determine whether exposure to certain chemicals results in adverse health effects • Compare dose of contaminant with incidence of adverse human health effect to ascertain relationship • Evaluate available toxicity information • Databases - IRIS • Identify data gaps • Investigate human health problems near the site

9. Risk Characterization • Combine the results of Exposure Assessment and Toxicity Assessment • Quantify risks to human health from individual chemicals and exposure pathways • Sum risks for various exposure scenarios • Evaluate cancer, non-cancer separately • Describe all assumptions, areas of uncertainty

10. Risk Assessment versus Risk Management • Risk assessment – unbiased scientific approach to assessing risk • Risk management – incorporates the results of risk assessment, factors in societal values, legal mandates, other considerations • Risk communication typically part of risk management

11. Communicating Risk • Human response to risk is not always rational • Level of risk play little role in acceptability to public • Emotional response often makes it difficult to communicate risk • People apply personal values when evaluating risk

12. Factors Affecting Risk Perception • Voluntary vs. Involuntary • Familiar vs. Unfamiliar

13. Catastrophic vs. Not Catastrophic • Natural vs. Man-made • Affects adults vs. Affects Children • Trusted vs. Untrusted Communicator • Equal vs. Unequal Benefits

14. Covello’s Cardinal Rules of Risk Communication • Accept and involve the public as a legitimate partner • Plan and carefully evaluate communication efforts • Identify audience, understand problems, pretest message • Listen to public’s specific concerns • Be honest, frank and open

15. Cardinal Rules Continued • Coordinate and collaborate with other credible sources • Meet needs of media • Speak clearly and with compassion

16. Arsenic in Drinking Water Case Study

17. A Bit of Arsenic Regulatory History • Original Public Health Service standard was 50 ug/L • Based on non-cancer endpoints • PHS standard grandfathered as EPA Maximum Contaminant Level in 1974 • 1986 Safe Drinking Water Act amendments directed EPA to review, revise arsenic MCL • Concern for skin cancer

18. Arsenic Risk Issues • Arsenic health effects have been extensively studied • A variety of human cancers are associated with arsenic ingestion • Lung, bladder, prostate, skin, liver… • Circulatory and neurological damage, diabetes also can occur • High disease levels seen in populations drinking water with arsenic 5-20 times higher than current 50 ug/L MCL (Taiwan study) • Epidemiology, medicine can at best resolve risks >1/100 level • For arsenic, exposures not high enough for epidemiology to find disease in U.S.

19. More Arsenic Regulatory History • In early 1990’s, new cancer concerns were growing • But strong opposition by oil, extractive and drinking water industries • 1996 SDWA amendments - new requirements for EPA to do cost-benefit decision-making • EPA proposed 5 ug/L as arsenic MCL in June 2000 • EPA promulgated MCL at 10 ug/L in January 2001 • New administration postponed effective date, set up review

20. Setting the MCL(Sublinear vs Linear Dose-Response) POD approximately 400 ppb X Cancer Arsenic levels in water MCLG=0 ppb

21. EPA Estimated Cancer Risks from Arsenic Ingestion(FR Notice Page 7008) • Other cancers not quantified, but add to risk

22. Cost and Benefits Comparison (from January 22, 2001 FR) Costs and benefits in $M/yr Also, unquantified health benefits for cancers of the skin, kidney, nasalpassages, liver, and prostate and noncancer effects on the cardiovascular, immune, nervous, and glandular systems likely to be substantial

23. Justification for 10 ug/L MCL • Result of Health Risk Reduction and Cost Analysis required by 1996 SDWA Amendments • 10 ug/L “more appropriately meets” HRRCA criteria than proposed 5ug/L • Second time since 1996 that EPA set MCL at greater than the feasibility level