Part 1d: Exposure Assessment and Modeling

Thomas Robins, MD, MPH

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

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.)

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 exposureEstimate exposure status & trends

A P P L I C A T I O N S

Exposure Assessment in Risk Assessment

Science“Objective”

Policy“Subjective”

Dose-Response

Assessment

Exposure Assessment

Risk Characterizatio

n

Risk Manageme

nt

Hazard Identification

Assessment of Regulatory Compliance

Evaluation of interventions to reduce exposureDisease diagnosis and treatment

Epidemiologic Studies

EXAMPLE: RISKS ASSOCIATED WITH A

NUCLEAR POWER PLANT

MAJOR COMPONENTS

reactormodel

containmentmodel

reactoraccident

sequences

healtheffects

groundcontamination

deposition

dispersion

evacuation

population

propertydamage

SOURCE

EXPOSURES

CONSEQUENCES

RELEASE ESTIMATE

• Identify risk-related events:-– human error– valve/pump failure– materials failures

•Quantify probability of each.

•Combine probabilities of risk-related event.

EXPOSURE ASSESSMENT

•Transport and fate of radioactive material:-– meteorological data– local terrain– location of potentially

exposed population– number of people potentially

exposed

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.

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.

MORE GENERALLY: EXPRESS RESULTS OF RISK ANALYSIS IN

TERMS OF . . .

• ProbabilityProbability that the number of adverse health effects is less than or equal to a given amount, oror

• ProbabilityProbability that the total number of people experiencing each health effect will equal or exceed a given value for a given time period, oror

• ProbabilityProbability that various sensitive groups will experience different levels of adverse health effect

. . . 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.

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

APPLICATIONS OF RESULTS OF SUCH

ANALYSIS . . .

?

Quantitativeestimates of risk

Political, economicconsiderations, etc.

policy and decisions