1. Part 1d: Exposure Assessment and Modeling Thomas Robins, MD, MPH

2. 1. DEFINITIONS OF EXPOSURE & EXPOSURE ASSESSMENT 2. APPLICATIONS OF EXPOSURE ASSESSMENT 3. EXPOSURE AND RISK 4. EXPOSURE ASSESSMENT METHODS 5. BIOLOGICAL MONITORING 6. COMPONENTS OF ENVIRONMENTAL EXPOSURE ASSESSMENT 7. COMMUNITY ENVIRONMENTAL EXPOSURE ASSESSMENT 8. OCCUPATIONAL EXPOSURE ASSESSMENT Outline

3. Exposure Assessment Measurement or estimation of the magnitude, frequency, duration, and route of exposure of humans, animals, materials, or ecological components to substances in the environment. The assessment also describes the size and nature of the exposed population. (US EPA) Determination of the sources, environmental transport and modification, and fate of pollutants and contaminants, including the conditions under which people or other target species could be exposed and the doses that could result. (Omenn GS, et al., 1997, Risk Assessment and Risk Management in Regulatory Decision- Making. Final report of the Presidential/Congressional Commission on Risk Assessment and Risk Management, Vols. 1 and 2., Washington DC.)

4. Applications of Exposure Assessment Environmental and Occupational Epidemiology Risk Assessment Risk Management Disease Diagnosis and Treatment Current & Historical Prospective Assessment of regulatory compliance Eval. of interventions to reduce exposure Estimate exposure status & trends APPLICATIONSAPPLICATIONS

5. Exposure Assessment in Risk Assessment Science “Objective” Policy “Subjective” Dose-Response Assessment Exposure Assessment Risk Characterization Risk Management Hazard Identification Assessment of Regulatory Compliance Evaluation of interventions to reduce exposure Disease diagnosis and treatment Epidemiologic Studies

6. EXAMPLE: RISKS ASSOCIATED WITH A NUCLEAR POWER PLANT

7. MAJOR COMPONENTS reactor model containment model reactor accident sequences health effects ground contamination deposition dispersion evacuation population property damage SOURCE EXPOSURES CONSEQUENCES

8. RELEASE ESTIMATE Identify risk-related events:- –human error –valve/pump failure –materials failures Quantify probability of each. Combine probabilities of risk- related event.

9. EXPOSURE ASSESSMENT Transport and fate of radioactive material:- –meteorological data –local terrain –location of potentially exposed population –number of people potentially exposed

10. CONSEQUENCE ASSESSMENT Health effects (from dose- response data):- –immediate fatalities/illnesses. –latent cancers (fatal/non-fatal). –genetic damage. Economic costs –cost of evacuation. –loss to agriculture. –decontamination. –population re-location.

11. RISK ESTIMATION FOR ADVERSE EFFECTS ASSOCIATED WITH THE NUCLEAR POWER PLANT Integrate to produce summary, quantitative measure of risk:- –estimation of probability of the various adverse outcomes (health effects, other outcomes), plus –error and confidence estimates.

12. MORE GENERALLY: EXPRESS RESULTS OF RISK ANALYSIS IN TERMS OF... Probability orProbability that the number of adverse health effects is less than or equal to a given amount, or Probability orProbability that the total number of people experiencing each health effect will equal or exceed a given value for a given time period, or ProbabilityProbability that various sensitive groups will experience different levels of adverse health effect

13. ... FOR EXAMPLE Risk (probability or fraction) that a person living in a particular part of the state will either/or:- - die prematurely - suffer from heart and lung ailments - suffer from asthma, etc. as a result of exposure to sulfate in the air arising specifically from emissions from the power plants within the state.

14. FURTHER QUANTIFYING RISK Sensitivity analysis to determine the effect of changes in each variable on the final estimate of adverse outcome. Quantify uncertainty: apply upper and lower bounds of each variable and determine outcome for each:- –statistical analysis; and/or –expert judgment

15. APPLICATIONS OF RESULTS OF SUCH ANALYSIS... ? Quantitative estimates of risk Political, economic considerations, etc. policy and decisions