Elimination and distribution of 2,2',4,5'-tetrachlorobiphenyl in laying hens.

Laying hens were given a single oral dose of 2,2',4,5'-tetrachloro[14C]biphenyl ([14C]TCB). Within 11 days of administration, 54.8% of the original dose was excreted in the faeces. Examination of eggs laid within this period showed that 11.7% of the original dose was present in the yolks. The biological half-life of [14C]TCB in hens was 7 days. In hens killed on day 7, radioactivity could be detected in all the main tissues and organs. In both faeces and yolk, about 60% of the radioactivity could be attributed to metabolites.