POLYCHLORINATED-BIPHENYLS (PCBS) IN FISH-EATING SEA BIRDS .2. MOLECULAR-FEATURES OF PCB ISOMERS AND CONGENERS IN ADIPOSE-TISSUE OF MALE AND FEMALE PUFFINS (FRATERCULA-ARCTICA), GUILLEMOTS (URIA-AALGA), SHAGS (PHALACROCORAX-ARISTOTELIS) AND CORMORANTS (PHALACROCORAX-CARBO) OF BRITISH AND IRISH COASTAL WATERS

1. The concentration of individual PCBs was measured in adipose tissue of male and female puffins, shags, guillemots and cormorants obtained from the Isle of May and the Saltees islands. 2. The concentrations of total PCBs showed positive correlations with that 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. Of the 47 individual PCBs identified five prominent PCBs had enrichment factors considerably > 1 and accounted for approximately 35% of the total concentration of PCBs present. They shared 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, which suggested that they had been subjected to metabolism and presumably excretion. They shared the common feature of the absence of chlorine atoms at the meta-para positions of the biphenyl rings. 6. These results support strongly the structural "rules" suggested in the preceding paper (Borlakoglu et al., 1990a) for the tendency of individual PCBs to accumulate or to be subjected to metabolism.