Metabolism of 2,2',5,5'-tetrachlorobiphenyl: formation of mono- and bis-methyl sulphone metabolites with a selective affinity for the lung and kidney tissues in mice.

1. Distribution in mice of 2,2',5,5'-tetrachloro[14C]biphenyl has been studied by autoradiography. Radioactivity was specifically localized in the bronchial epithelium, the lung parenchyma, the kidney cortex and the adipose tissue. 2. Bis(methylsulphonyl)-2,2',5,5'-tetrachlorobiphenyl, a hitherto unknown metabolite of 2,2',5,5'-tetrachlorobiphenyl, has been identified in lung, kidney and liver of mice. 3- and 4-Methylsulphonyl-2,2'5,5'-tetrachlorobiphenyl were also present. 3. The ratio of the contents of 3- and 4-methylsulphonyl-2,2',5,5'-tetrachlorobiphenyl in the liver was 1.12 after 12 days. A lower ratio in lung and kidney indicates a high affinity of these tissues for the 4-methyl isomer.