Short-term dermal absorption and penetration of chemicals from aqueous solutions: Theory and experiment

Dermal penetration of organic chemical-contaminated water from showering an d bathing scenarios is a concern of regulatory agencies that have been task ed with determining safe exposure levels. During household showering and ba thing, nearly the entire surface area of the body is exposed for short peri ods of time (5-15 minutes). The primary means of predicting body burden dur ing brief exposures is to estimate total chemical penetrated from the stead y-state penetration rate using a skin permeability coefficient. A variety o f approaches has been recommended to estimate "body burden." The purpose of this investigation was to collect experimental data from short-term exposu res to an organic chemical (dibromomethane [DBM]) in aqueous solution so th at methods for estimating body burden could be compared. Rat skins were exp osed in vitro to saturated aqueous solutions of DBM for 20 minutes and the amount of chemical in the receptor solution and the skin was analyzed. The total DBM mass in the receptor solution and the skin was taken to represent an in vivo body burden. These results were compared with the estimates of penetration from steady-state calculations, square root of time calculation s, and a biologically based mathematical model. Results indicated that the amount of chemical in the skin and its fate during short exposures is impor tant. The square root of time approach predicted total amount of chemical a bsorbed and penetrated better than did the steady-state approach. The biolo gically based mathematical model accurately predicted total body burden and could be used to distinguish between the amount of chemical in the skin an d the amount of chemical that penetrated through the skin, which would be u seful for understanding local toxicity.