Percutaneous and Oral Absorption of Chlorinated Paraffins in the Rat

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Abstract
Parallel percutaneous absorption studies of two14 C-labelled chlori nated paraffins (C18, 50-53% chlorination; C28, 47% chlorination) were carried out in the Sprague-Dawley rat. The dermally applied dose (66 mg/cm2) was approximately equivalent to 2.0 g/kg of body weight. An oral absorption study with the C18-chlorinated paraffin (0.5 g/kg) was carried out in rats for comparison. Less than 1% of the dermally applied dose of [1- 14 C]polychloro octadecane (50-53% chlorination) and less than 0.1% of the applied dose of [14,15-14 C]polychlorooctacosane (47% chlorination) were recovered in excreta, expired air and tissues after 96 hours. In con trast, approximately 86% of the orally administered dose of [1-14 C] polychlorooctadecane (0.5 g/kg) was recovered. These results indi cate that rat skin acts as an effective barrier to chlorinated paraffins containing eighteen or more carbons and more than 40% chlorine by weight. The oral absorption of the C18 chlorinated paraffin can be estimated to be nearly 100 times greater than its dermal absorp tion. Based on current toxicity results from rodent experiments and these present findings, chlorinated paraffins of the type tested would be expected to have little or no effect in animals as a result of dermal exposure. It is reasonable to assume that such chlori nated paraffins are unlikely to be systemically toxic to humans by skin contact under normal conditions of production and use.