Effects of soil on percutaneous absorption of toluene in male rats.

Previous assessments of health risks from soil-adsorbed chemical exposures relied on extrapolations from data derived with pure compounds. However, interactions between chemical and soil can alter the rate, amount, and form of chemical that enters the body, resulting in effects that are different from those that occur after exposures to chemical alone. In this study, male rats were treated dermally with [14C]toluene alone or adsorbed to either a sandy or a clay soil. Both soils produced a higher plasma concentration compared to pure toluene, with a statistical decrease in half-life of absorption observed after sandy soil-adsorbed treatment. The time to reach peak plasma concentration, half-life of elimination, and area under the plasma concentration-time curve (AUC) were similar for all groups. Skin and fat contained the highest concentration of radioactivity 48 h after all treatments. Pure and soil-adsorbed toluene were primarily metabolized and excreted via the kidney rather than exhaled. Furthermore, soil treatment did not alter the percentages of the metabolic products.