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Step 2.1 Estimating Exposure Doses

Estimating a Dermal Contact Dose: When and How?

When? Dermal contact doses should be estimated when the chemical being evaluated is one that can pass through a person’s skin or when most of the skin on a person’s body is exposed to a chemical, for example, while swimming.

How? Dermal contact doses are estimated as follows.

Multiply the chemical level by the intake rate. Then multiply by the exposure factor. Now divide the product by the body weight.

To calculate the intake rate for dermal contact with chemicals in water, multiply the chemical-specific permeability constant by the area of skin exposed.

To calculate the intake rate for dermal contact with chemicals in soil, multiply the soil adherence factor by the area of exposed skin. Then multiply by the chemical-specific bioavailability factor.

Chemical-specific permeability constant

A chemical-specific permeability constant is a number that expresses the rate at which a chemical moves through the skin. The number is derived from experimental studies.

Soil adherence factor

The soil adherence factor is an estimate of how much of a particular soil type will stick to a person’s skin after contact.

References for chemical-specific permeability constants and soil adherence factors

EPA Exposure Factor Handbook, EPA Soil Screening Guides, and EPA RAGs.

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