Risk Assessment 1

Thanks to Paul R. Harp, Ph.D., NH Department of Health & Human Services, US EPA Air

Quality Planning & Standards Division, and the DOE Risk Assessment

Information System.

Crispin Pierce, Ph.D.

University of Washington

The hazard identification process determines whether exposure to a chemical can increase the incidence of a particular adverse health effect and determines the likelihood of occurrence in humans.

Hazard Identification

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Exposure Assessment

The dose-response assessment describes the relationship between the magnitude of exposure and the appearance and duration of adverse effects.

Dose-Response Assessment

Airborne concentration

Toxicity

Set Standards

•Review toxicity and exposureassessment output

•Quantify risks

•Combine risks across all pathways

•Assess & present uncertainties

•Consider site-specific human studies, if available

•Summarize & present baseline riskassessment characterization results

Risk Characterization

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• How would you sort out the incidence of disease related to toxicant exposure vs. the background incidence?

• Should people who have both personal and occupational exposure to the same toxicants have different standards than those who don’t? (e.g., should smokers have lower occupational formaldehyde exposure limits?)

• Should pregnant women be excluded from jobs where reproductive toxicant exposure occurs?

Activities Perceived as Higher Risk by:the United States Environmental Protection Agency (EPA)

Global warming

Indoor air pollution, including radon (high health risk)

Exposure to chemicals in consumer products (high health risk)

Surface water pollution (high ecological risk)

by the Public

Chemical waste disposal

Water pollution

Chemical plant accidents

Perception of Risk

Activities Perceived as Lower Risk by:

the EPA

Hazardous waste sites - active and inactive

Underground storage tanks

the Public

Indoor air pollution

Exposure to chemicals in consumer products

Global warming

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• Should taxpayer dollars be spent on reducing the highest risks determined by experts (e.g., the EPA) or by the public?

Cancer vs. Non-Cancer Endpoints

No (or Lowest) Observed Adverse Effect Level

• Additional UF between 1 and 10.• Allows professional assessment of additionaluncertainties not accounted for by the UF.• Default is 1.

Modifying Factor

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• How would you set exposure standards for simultaneous exposure to two chemicals that targeted the same organ?

Weight of Evidence for Cancer Risk

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• In 1763, Reverend Edmund Stone effectively treated fever with the bark from willow trees. The effective ingredient turned out to be salicylic acid. This drug has been used in different forms since then, and has shown good efficacy and low toxicity in treating fever, pain, and arthritis. However, acetylsalicylic acid is teratogenic in mice, rats, and hamsters. How do you approach this controversy in deciding whether or not to approve this drug for use?