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

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Indirect Estimation
(Scenario Evaluation)

Exposure Factors

Exposure factors are factors related to human behavior and characteristics that help determine an individual's exposure to an agent. These factors can include, for example, rates of ingestion (e.g., foods, soil, water) or inhalation, factors affecting dermal exposure (e.g., skin surface area, soil-to-skin adherence), activity factors (e.g., time spent indoors, time spent showering, etc.), or other factor (e.g., body weight, consumer products use).

The main sources of exposure factors data are EPA’s Exposure Factors Handbook: 2011 Edition (U.S. EPA, 2011a) and Highlights of the Exposure Factors Handbook (U.S. EPA, 2011b). In 2008, EPA published a Child-Specific Exposure Factors Handbook (CSEFH) (U.S. EPA, 2008) and Highlights of the Child-Specific Exposure Factors Handbook (U.S. EPA, 2009) to consolidate data relevant for assessing childhood exposures. However, the Exposure Factors Handbook: 2011 Edition supersedes the CSEFH. The 1997 edition of the Exposure Factors Handbook (U.S. EPA, 1997a) archive is still available for reference.

Both the Exposure Factors Handbook: 2011 Edition and the CSEFH provide statistical information for factors used in assessing exposure among various demographic groups of the population. Information is provided on intake of water and selected liquids; non-dietary ingestion factors; ingestion of soil and dust; inhalation rates; dermal exposure factors; ingestion of fruits, vegetables, meats, dairy products, fats, fish, shellfish, grains, home-produced foods, total dietary intake, and human milk; activity factors; consumer products; and building characteristics. The Handbook does not include chemical-specific data or information on physiological parameters that may be needed for exposure assessments involving physiologically based pharmacokinetic (PBPK) modeling.

Information from the Exposure Factors Handbook: 2011 Edition and data and resources used in developing the recommendations provided in the Handbook may be accessed using the button links below or there is a summary of the recommended values in spreadsheet format. It is important to note that these recommendations are not legally binding on any U.S. EPA program and should be interpreted as suggestions that program offices or individual exposure assessors can consider and modify as needed. And finally, tables from the handbook can be identified from the EPA-Expo-Box's Exposure Factor Tables Search. A selected number of these tables are available in spreadsheet format. These tables were selected because they contain distributional information that may be suitable for probabilistic analyses.

There are similar efforts in other countries that provide data on exposure factors. For example, The European Union developed the ExpoFacts database Exit EPA Disclaimer which contains data from 30 European countries. Likewise, Japan have developed the Japanese Exposure Factors Handbook Exit EPA Disclaimer and Australia have developed the Australian Exposure Factor Guide (87 pp, 4.45MB, About PDF) Exit EPA Disclaimer; these resources provide data specific to each country’s population.

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