Hepatocarcinogenicity of PCB congeners

Abstract

Since about 1980 only technical mixtures of low‐chlorinated biphenyls have been used in the Federal Republic of Germany. Although these are more readily degraded in the environment than mixtures containing high‐chlorinated compounds, low‐chlorinated congeners such as PCB No. 49 (2,2’,4,5') have entered the food chain and are detectable in foodstuffs and in human breast milk. In order to estimate the hepatocarcinogenic properties of low‐chlorinated PCB congeners, we determined their ability to initiate and to promote focal alterations of preneoplastic enzymes in rats. The low‐chlorinated 2,2’,4,5'‐tetra‐chlorobiphenyl which can be metabolised, was compared to the high‐chlorinated and persistent PCB No. 153 (2,2'4,4'5,5'‐hexachlorobiphenyl). PCB No. 49 initiated ATPase‐negative foci in rat liver. Administration of both congeners resulted in growth promotion of ATPase‐deficient‐foci and GGTase‐positive foci initiated by diethylnitrosamine. The promoting ability of the two congeners was approximately equal.