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EPA-Expo-Box (A Toolbox for Exposure Assessors)

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Tiers and Types

Exposure assessment is one of the four major steps in risk assessment; others include hazard identification, dose-response assessment, and risk characterization. Exposure assessment is “the process of estimating or measuring the magnitude, frequency, and duration of exposure to an agent, along with the number and characteristics of the population exposed. Ideally, it describes the sources, routes, pathways, and uncertainty in the assessment” (EPA’s Guidelines for Exposure Assessment (U.S. EPA, 1992) and IPCS, 2004 Glossary of Key Exposure Assessment Terminology (122 pp, 951KB, About PDF) developed by the International Programme on Chemical Safety). 

Exposure may be estimated using one of several assessment tiers or types:  screening-level and refined, deterministic and probabilistic, or aggregate and cumulative. Tools related the various assessment tiers and types are provided in EPA-Expo-Box. Alternatively, exposure assessments may be categorized according to exposure assessment approaches, exposure media, exposure routes, lifestages and populations, or chemical classes.

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