Percutaneous absorption of [14C]chlordane from soil.

The objective was to determine percutaneous absorption of chlordane in vitro and in vivo from soil into and through skin. The data are needed to calculate the absorbed dose of chlordane from soil, which is then used to assess the toxicity risk. Chlordane, an insecticide for which residues exist in soil, is restricted currently to use for termite control. Chlordane is highly lipophilic with little or no movement out of soil. Soil (Yolo County 65-California-57-8; 26% sand, 26% clay, 48% silt, 0.9% organic) was passed through 10-, 20-, and 48-mesh sieves. Soil then retained by 80-mesh was mixed with 14C-labeled chemical at 67 ppm. Acetone solutions were prepared for comparative analysis. Human cadaver skin was dermatomed to 500 microns and used in glass diffusion cells with human plasma as the receptor fluid (3 ml/h flow rate) for a 24-h skin application time. Chlordane concentration within skin from in vitro studies was 0.34 +/- 0.31% from soil and 10.8 +/- 8.2% from acetone vehicle (p less than .01). Individual variation from human skin sources was evident (p less than .008). Chlordane accumulation in human plasma receptor fluid was the same for soil (0.04 +/- 0.05%) and acetone (0.07% +/- 0.06%) formulations. Most of the remaining chlordane was recovered in the soap and water skin surface wash. In contrast, in vivo percutaneous absorption of chlordane in the rhesus monkey was the same for soil (4.2 +/- 1.8%) and acetone (6.0 +/- 2.8%) formulations (p = .29, nonsignificant). Multiple soap and water washings were necessary to remove chlordane from skin, suggesting that a single wash may not adequately remove all the chlordane.

Comparative disposition and elimination of chlordane in rats and mice.

The absorption, distribution and elimination of orally administered cis-[14C]chlordane (1.0 mg/kg) was determined in male Sprague-Dawley rats and C57BL/6JX mice. Absorption appeared somewhat slower in mice, but total [14C]chlordane equivalents at peak blood concentration (113 ng/ml at 8 h) exceeded the maximum which occurred in rats (81 ng/ml at 2 h). Peak tissue residues in both species were observed within 4 h, suggesting that the radiocarbon responsible for the latent peak blood levels in mice was eliminated rather than sequestered by the tissues. This was supported by the findings that peak tissue residue levels were lower in mice, and that the initial fecal elimination rate was higher than in rats. At 12 h, 34% and 7% of the doses were excreted in mouse and rat feces, respectively; by 3 days, both species had voided 83% of the dose in the feces. Clearance rates of tissue residues were markedly faster in the rat, and consequently, the total body burden resulting from chronic exposure to chlordane will be far greater in mice than in rats.