Subchronic toxicity of a medium-chain chlorinated paraffin in the rat

Groups of ten male and female weanling Sprague‐Dawley rats were fed diet containing 0, 5, 50, 500 or 5000 ppm of a medium‐chain chlorinated paraffin (C14‐17, 52% chlorination) for a period of 13 weeks. Increased relative liver weight was observed at 500 and 5000 ppm in females and at 5000 ppm in males. Relative kidney weight was increased at 5000 ppm in both sexes. Serum cholesterol was increased in the females in a dose‐related manner starting at 50 ppm. At 5000 ppm, animals of both sexes had elevated hepatic UDP‐glucuronosyltransferase activity while only females showed increased aminopyrine N‐demethylase activity. Increased urinary N‐acetylglucosaminidase activity occurred at 5000 ppm in females. Increased urinary ascorbic acid excretion monitored at week 12 and a decreased hepatic vitamin A level were detected in females receiving the 500 ppm diet and male and female rats at 5000 ppm. Mild, adaptive histopathological changes were detected in the liver of rats of both sexes at 500 and 5000 ppm, and in the thyroid of males and females starting at 500 and 50 ppm, respectively. Minimal changes were observed in the kidney proximal tubules of male rats fed the 5000 ppm diet and in the inner medulla tubules of female rats fed the 500 and 5000 ppm diets. These data indicate that the medium‐chain chlorinated paraffin produces biochemical and histological changes at dietary levels of ± 50 ppm in females and ± 500 ppm in males.