COMPARATIVE CARCINOGENICITY IN SPRAGUE-DAWLEY RATS OF THE POLYCHLORINATED BIPHENYL MIXTURES AROCLOR-1016, AROCLOR-1242, AROCLOR-1254, AND AROCLOR-1260

A comprehensive chronic toxicity and carcinogenicity study was conduct ed on a series of Aroclors (1016, 1242, 1254, and 1260). Each Aroclor was assessed at multiple dietary concentrations, ranging from 25 to 20 0 ppm, for 24 months in male and female Sprague-Dawley rats. Liver tox icity was indicated by elevated serum enzyme activity (AST, ALT, and G GT), elevated serum cholesterol concentration, decreases in hematologi c parameters (RBC, Hb, and Hct), hepatocellular hypertrophy, an increa sed incidence of altered hepatocellular foci, and an increased inciden ce of hepatocellular neoplasms (primarily adenomas). Liver toxicity wa s distinctly more severe in females than in males. The incidence of he patocellular neoplasms was highly sex-dependent (females much greater than males), differed between Aroclor mixtures and, for females, incre ased with dose and followed the general incidence pattern of Aroclor 1 254 > Aroclor 1260 approximate to Aroclor 1242 > Aroclor 1016. A signi ficant response (p < 0.05) in males was seen only for the high dose of Aroclor 1260. A small increase in the incidence of thyroid gland foll icular cell adenomas was noted in males for Aroclors 1242, 1254, and 1 260, with the incidence being uniform across dose groups and Aroclor m ixtures. For females, increased survival relative to controls was obse rved for all Aroclor treatment groups. A significantly decreased trend in the incidence of mammary gland neoplasms compared to control was a lso noted for females receiving Aroclors 1242, 1254, and 1260. (C) 199 8 Society of Toxicology.