POLYCHLORINATED-BIPHENYLS (PCBS) IN FISH-EATING SEA BIRDS .1. MOLECULAR-FEATURES OF PCB ISOMERS AND CONGENERS IN ADIPOSE-TISSUE OF MALE AND FEMALE RAZORBILLS (ALCA-TARDA) OF BRITISH AND IRISH COASTAL WATERS

1. The concentration of individual PCBs was measured in adipose tissue of male and female razorbills obtained from the Isle of May and the Saltees islands. 2. No significant differences were found in the concentration of total PCBs, which showed positive correlations with the concentration of p,p'-DDE in the tissues. 3. Enrichment factors were calculated by comparing the concentration of an individual PCB in the tissue with its abundance in commercial mixtures of PCBs. 4. Eight PCBs, together accounting for 20-65% of the concentration of total PCBs present, had enrichment factors of > 10. They had the common molecular feature of chlorine atoms at adjacent meta-para positions in at least one of the biphenyl rings. 5. Many PCBs had enrichment factors of < 1, suggesting that they had been subjected to metabolism and presumably excretion. They had, in common, the absence of chlorine atoms at the meta-para positions of the biphenyl rings.