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

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Soil and Dust

Exposure Factors

To estimate human exposure to contaminants in soil and dust, exposure factor information is needed. Exposure factors are human behaviors and characteristics that help determine an individual's exposure to an agent. They may include ingestion rates, and the factors that affect dermal exposure such as body surface area, dermal adherence of solids to skin, and dermal transfer factors. (See the Air Module in the Media Tool Set for information on evaluating inhalation exposures to indoor or outdoor dust that is airborne. Occupational exposure to airborne dust is also addressed in the Exposed Populations Tool Set of EPA-Expo-Box.)

Data on soil and dust ingestion rates are available in Chapter 5 of EPA’s Exposure Factors Handbook: 2011 Edition. Ingestion rates are reported in units of mg/day. Ingestion rates should be selected to represent the appropriate medium (soil, dust, or soil + dust combined); age/lifestage; and intake category (general population, soil pica, or geophagy). As described in the Handbook, the ‘soil + dust’ medium includes outdoor soil; containerized indoor soil; dust that is a combination of outdoor settled dust, indoor settled dust, and airborne particulate matter that is inhaled and subsequently swallowed; and outdoor soil that has been tracked indoors.

Body surface area, activity-specific soil adherence factors, and skin transfer efficiencies needed for assessing dermal contact with soil and dust are available in Chapter 7 of the Handbook. Chemical-specific factors related to dermal absorption and internal dose, however, are not provided in Chapter 7. Activity-specific factors that may be relevant for assessing exposures involving dermal contact with soil or dust are available in Chapter 7 and Chapter 16 of the Handbook, and these might include time spent indoors, time spent outdoors, or time spent doing specific activities (e.g., playing on dirt or grass, gardening, participating in outdoor recreation).

Other exposure factors that might be needed for assessing ingestion exposures include:

  • Body weight (Chapter 8)
  • Life expectancy values, specifically when evaluating cancer risk (Chapter 18)

Exposure factor data may be accessed from the Exposure Factors Tab of the Indirect Estimation Module.

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