ABSTRACT
Bowman and Wahlberg conducted an excellent study in guinea pigs that showed that effect of skin damage on blood levels is opposite for hydrophilic and hydrophobic chemicals. The effects of regional variations, elevated temperature, hydration, soaps, and surfactants are difficult to quantify and probably contribute modestly in most cases. Permeability coefficients are most commonly estimated by dividing the steady-state flux from diffusion cells or whole animal studies by the exposure concentration. Since both mass and volume based partition coefficients are unitless, it is difficult to know which type is reported, unless the authors have specified. Pharmacokinetic models may be used to estimate total absorption from blood, exhaled breath, or tissue concentrations in direct studies. Pharmacokinetic models of dermal uptake are generally used to predict absorption, distribution, metabolism, and elimination of chemicals after dermal exposure. Damaged skin might impact the dermal uptake of chemicals from contaminated water if the ratio of damaged surface area to total surface area exposed becomes significant.
