Soil adsorption alters kinetics and bioavailability of benzene in orally exposed male rats.

Abstract

A study comparing the bioavailability of pure vs soil-adsorbed benzene was conducted in adult, male rats. Animals were gavaged with an aqueous suspension of benzene alone or adsorbed to either a Keyport series (clay soil) or a Cohansey aquifer solid (sandy soil) from New Jersey. Peak plasma concentration of radioactivity was increased in the presence of either soil vs benzene alone while the sandy soil also decreased the time to reach peak vs benzene alone. Either soil produced an increase in the area under the plasma radioactivity-time curve versus benzene alone, while the clay soil did so in a statistically significant manner. The half-life (t1/2) of absorption into plasma was not statistically different in the presence of either soil, while each soil decreased the t1/2 of elimination vs benzene alone and clay soil did so in a statistically significant manner. Two hr after exposure, stomach tissue contained the highest amount of radioactivity followed by fat in all treatment groups. No differences were detected in the tissue concentration of radioactivity between the treatment groups. Expired air was the primary excretion route following exposure to benzene alone with lesser amounts of radioactivity eliminated in the urine during the 48 hr following exposure. The opposite pattern was detected in the presence of clay soil, while expired air and urine represented approximately equal routes of excretion in the presence of sandy soil. Unmetabolized benzene represented the bulk of total radioactivity in the expired air of all treatment groups with [14C]O2 comprising the remainder. Less than 2% of radioactivity was eliminated by the fecal route for all treatments with significantly higher amounts in the clay soil treatment versus benzene alone. Phenol was the primary benzene metabolite detected in the 0–12 hr urines of all treatment groups. Lesser amounts of hydroquinone, catechol, and benzenetriol were also detected. No differences in the metabolite percentages were detected between the treatment groups.