Evaluation of PCBs and PCDD/Fs retention by aquatic organisms

Patterns of PCBs, PCDDs and PCDFs were examined in prey and predator species from Lake Ontario. Differences in PCB isomer retention were exceeded several fold for Cl-3-Cl-5 homologues in trout, and less than 1 fold for the few PCDD/F values available. Differences in retention were evaluated on the basis of chemical uptake and elimination rates, and biochemical factors that might influence their metabolism. Dietary absorption was not an important variable in the retention of PCBs, but was for PCDD/Fs. Structure-related properties of PCBs that enhance their metabolism were compiled from mammalian studies. Configurations like non-ortho substituted CBs are strong CYP-450 inducers, but are not associated with their metabolism in fish. Hydroxylation at the para position enhances the elimination of some lower chlorinated CBs, but no substitution patterns consistently explained the differences in retention among congeners. Further evaluation of the more common substitution patterns associated with CB behavior indicate a surprisingly large number of similarities among the 209 congeners. Examination of chemical transfer from sediment to aquatic;organisms indicated large differences in behavior between PCBs and PCDD/Fs. Biota/sediment accumulation factors for trout averaged 102 among 61 CB isomers, while factors for two 2,3,7,8-substituted PCDD/Fs were below 3 and most were well below 1. Non-2,3,7,8-substituted congeners are also major contributors to Sigma PCDD/F concentrations in sediment and biota.