A COMPARATIVE-STUDY OF THE KINETICS AND BIOAVAILABILITY OF PURE AND SOIL-ADSORBED NAPHTHALENE IN DERMALLY EXPOSED MALE-RATS

The aim of this study was to utilize pharmacokinetic techniques to ass ess the bioavailability of sandy or clay soil-adsorbed naphthalene vs chemical alone following dermal treatment of male rats. Animals were e xposed to 43 mu g total of C-14-naphthalene (pure or adsorbed to one o f two soils) introduced into a shallow glass cap covering a 13-cm(2) a rea on the skin of each rat. While both soils delayed the time to reac h maximum plasma concentration of radioactivity and significantly incr eased the half-life of plasma absorption, only sandy soil significantl y decreased the peak plasma concentration of radioactivity versus the pure compound. Within 12 h after dermal application, approximately 50% of the naphthalene dose was excreted in the urine of the pure and cla y soil-adsorbed groups. However, when naphthalene was adsorbed to sand y soil, the percentages of the initial dose excreted in the urine coll ected between 0-12 h and 12-24 h were nearly equal (33-39%). Furthermo re, sandy soil adsorption shifted the secondary excretion route from e xpired air to feces and significantly lowered the amount of radioactiv ity in expired air relative to naphthalene alone. In the presence of s andy soil, a significantly larger amount of radioactivity washed off o f the skin application sites. In all groups the predominant urinary me tabolites determined by high performance liquid chromatography were 2, 7- and 1,2-dihydroxynaphthalenes.