Estimation of dermal absorption using the exponential saturation model

Estimates of dermal absorption are used in exposure assessment to calculate the internal dose of persons contacting pesticides and are a critical part of risk assessments. An exponential saturation model with lag time was val idated against a classic dermal absorption study of 12 pesticides administe red to human volunteers. The model gave dermal absorption estimates consist ent with reported values in the literature. Moreover, this model gave more realistic estimates of the percentage of dermal absorption for some pestici des, which have special properties. Inmost submitted dermal absorption stud ies in animals, especially rats, "bound" skin residues (ESR) at treated ski n sites were generally high when animals were sacrificed more than 24 h aft er the dose was administered. The direct addition of the total BSR as an ab sorbed dose would likely overestimate actual dermal absorption. From a well -conducted dermal absorption study, this model can be utilized to estimate maximum excretion of the administered dermal dose as a result of further ab sorption of bioavailable BSR. Resulting dermal absorption estimates are app ropriate for regulatory purposes in the risk assessment of pesticides becau se they take into account the bioavailability of BSR while at the same time the estimates are not overly conservative. (C) 1999 Academic Press.