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

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Soil and Dust

Exposure Scenarios

Exposure to contaminants in soil or indoor settled dust can be estimated by first defining the exposure scenario of interest. Exposure scenarios typically include information on the sources and pathways of exposure, contaminants of concern, and receptor populations. They might also describe a receptor population’s activities that may affect exposure and the timeframe over which exposure occurs.

Exposure to soil and dust can occur by intentional ingestion (e.g., pica or geophagy), incidental ingestion (e.g., from hand-to-mouth contact), or via dermal contact (see the Air Module in the Media Tool Set for information on evaluating inhalation exposures to indoor or outdoor dust that is airborne). Dermal contact with soil could occur during outdoor recreational, gardening, or construction-related activities. Receptors could also come into contact with contaminants in soil and dust that have settled on carpets, floors, clothing, counter tops, or other surfaces. Ingestion of soil and dust are potential routes of exposure for children and adults; however, children are particularly susceptible to these soil and dust exposures because certain behaviors (e.g. tendency to mouth objects or hands) and activities (e.g., playing on the ground outdoors; crawling or playing on the floor indoors) may increase their contact with soils and dust. For soil/dust ingestion and dermal contact scenarios, concentrations of the contaminants in soil/dust are needed to estimate exposure or dose (see the module on Lifestages in the Lifestages and Populations Tool Set of EPA-Expo-Box for information on assessing exposure to children).

After characterizing the exposed population and identifying exposure concentrations, it is important to define all appropriate exposure factor inputs used to estimate potential exposures and risks, and these inputs (intake rates, dermal contact rates, and other relevant patterns of behavior) can be obtained from the Exposure Factors Handbook: 2011 Edition (see Exposure Factors tab in the Indirect Estimation Module of Approaches Tool Set).

The table below provides some additional examples of scenarios involving contaminants in soil and dust. The list of examples is not meant to be exhaustive; there are numerous other ingestion and dermal scenarios that may be constructed based on the specific needs of the assessment. There are also numerous variations of the examples provided in the table. Additional information on exposure scenarios involving contaminated air may be found in the Indirect Estimation Module in the Approaches Tool Set of EPA-Expo-Box.

Examples of Exposure Scenarios Involving Soil and Related
Exposure Factor Handbook: 2011 Edition Tables
Medium/Route Receptor Population Relevant Activity Pattern Intake Rate/Skin Contact Exposure Period
Soil and dust ingestion Residential children Residence time (mobility)
[Table 16-4]
Child soil and dust ingestion rate (mg/day)
[Table 5-1]
Acute or subchronic
Indoor Dust ingestion School children Time spent at school
[Table 16-17]
Child soil and dust ingestion rate (mg/day)
[Table 5-1]
Subchronic
Soil and dust ingestion Adults gardeners Residence time (mobility)
[Table 16-4]

Time spent working with soil in garden
[Table 16-44]
Adult soil and dust ingestion rate (mg/day)
[Table 5-1]
Chronic
Soil and dust dermal contact Adults gardeners Residence time
[Table 16-4]

Time spent working with soil in garden
[Table 16-44]
Adult skin surface area
[Table 7-2]
and soil adherence factor
[Table 7-4]
Chronic

Several resources are available that illustrate soil and dust exposure scenarios.

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