Toxicity of the chlordane metabolite oxychlordane in female rats: clinical and histopathological changes.

Due to widespread usage of the pesticide chlordane until the 1980's, this toxic and persistent mixture has accumulated in the food chain. The Arctic acts as a global sink for these and other persistent organic pollutants, which bioaccumulate in the marine and freshwater food chains. As a result, humans consuming diets high in Arctic fish and marine mammal fat can ingest higher levels of chlordane contaminants than humans consuming "southern" diets. The most abundant constituents of the chlordane mixture are trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor and heptachlor; oxychlordane is the major metabolite of the chlordanes and nonachlors. In humans the predominant chlordane-related contaminants detected in breast milk and adipose tissues are trans-nonachlor and oxychlordane. The present studies were undertaken to provide toxicological data on oxychlordane for the purpose of clarifying target organ toxicity and risks to human health associated with ingesting contaminated foods. Female rats were gavaged with oxychlordane at doses ranging from 0.01 to 10 mg/kg body weight/day for up to 28 days. In terms of general toxicity oxychlordane had a steep dose-response curve: 10 mg/kg oxychlordane was acutely toxic and 1 mg/kg oxychlordane caused no measurable effects. Weight loss, reduced feed consumption and thymic atrophy were the hallmarks of acute oxychlordane toxicity. At lower doses rats showed signs of hepatic changes indicative of microsomal enzyme induction. Oxychlordane was more bioaccumulative and was toxic at levels approximately 8 times lower than trans-nonachlor and cis-nonachlor. Thus, ingestion of trans-nonachlor and related chlordane contaminants in foods results in the formation of a metabolite that is more toxic and bioaccumulative than the parent contaminants.