Distribution and elimination in vivo of polychlorinated biphenyl (PCB) isomers and congeners in the pigeon

1. Pigeons were injected with a single dose of commerical PCB mixtures (Aroclor 1248 plus Aroclor 1260), killed 120 h later and the abundance of individual PCBs was determined in adipose tissue, gonads, liver, brain, kidney, heart, muscle and blood.

2. Elimination factors for individual PCBs were calculated. Values of >1 were obtained for PCBs with meta-para-unsubstituted carbon atoms in at least one ring, indicating that elimination exceeded accumulation in all or most tissues. By contrast, ortho-meta unsubstituted PCBs had elimination factors <1, thus indicating their impaired removal.

3. Tissues with high microsomal monooxygenase activity had the highest elimination factors for individual PCBs (i.e. liver> kidney > muscle > heart).

4. Distribution of individual PCBs was independent of sex and of ortho-chlorine substitution and showed that 90% of total PCBs in cadavers was present in adipose tissue, 2% in kidneys, 1% each in brain, muscle and heart and <0.1% in blood.

5. The distribution of the highly toxic non-ortho and mono-ortho substituted PCBs did not differ amongst all tissues analysed.

6. The present studies indicate that elimination of PCBs in vivo is favoured by the molecular feature of unsubstituted meta-para carbon atoms in the biphenyl moiety.