Correction factors for determining body exposure from forearm percutaneous absorption data.

Evaluation of toxic exposure via the skin is invariably based upon forearm percutaneous absorption data and an appropriate area multiplication factor. Published experimental data clearly show, however, substantial site variation in skin penetration such that the use of forearm data may produce an inaccurate prediction of total body exposure. Using literature results for cutaneous absorption as a function of anatomic position and accepted estimations of human body surface areas, correction factors for use with forearm penetration data have been evaluated. Calculations have been performed for an adult, a small child and a neonate. Examples of limited exposure to specific regions of the body have also been assessed relative to predictions based upon percutaneous absorption across forearm skin. It appears that the use of forearm skin penetration data alone underestimates body exposure by at least a factor of two.