Step 2.1 Estimating Exposure Doses

Site-Specific Exposure Information

The types of information needed to estimate an exposure dose are referred to as exposure factors. That information is based on site-specific conditions.

Following are explanations of several types of information used in estimating exposure doses.

Exposure point level refers to the level of a chemical that is present at the point when an individual comes in contact with it.

The intake rate is the amount of a chemical taken into a person's body during time of contact with the chemical. Intake rates are calculated separately for each way that a chemical enters a person's body.

Exposure frequency refers to how often a person comes in contact with a chemical.

Exposure duration refers to how long a person has been contacting the chemical.

Population characteristics are the demographic and social characteristics of people in the community.

Three types of site-specific information that can be used for evaluating exposures are community interviews, observations made at the site, and contacts who are knowledgeable about the site.

What information does an assessor use when estimating exposure doses?

A health assessor must use all information about a site and the characteristics of the population when estimating exposure doses. For example, a health assessor evaluating health conditions in a community near rivers where fish had been found to contain harmful levels of chemicals would estimate exposure doses for people in the community depending on the amount of fish in their diets.

ATSDR's Public Health Assessment Guidance Manual

ATSDR's Public Health Assessment Guidance Manual provides health assessors with guidelines for conducting public health assessment activities.

The manual is available online at http://www.atsdr.cdc.gov/HAC/PHAManual/ . (Information about doses and health guidelines can be found in Appendix G.)

Where does the health assessor find information on exposure factors when site-specific information is not available?

The U.S. Environmental Protection Agency's Exposure Factors Handbook

EPA's Exposure Factors Handbook summarizes the available statistical data on various types of information used in estimating human exposure doses. The exposure factors provided in the handbook should only be used if no site-specific information is available.

The Exposure Factors Handbook and updates to the handbook are available online at https://hero.epa.gov/hero/index.cfm/project/page/project_id/1854.

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