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.

dose=

where,

the intake rate for dermal contact with chemicals in water = (the area of skin exposed × the chemical-specific permeability constant)

or

the intake rate for dermal contact with chemicals in soil = (the area of skin exposed × soil adherence factor × chemical-specific bioavailability factor)

References for chemical-specific permeability constants and soil adherence factors