| Summary: | The enantiomeric composition of polychlorinated biphenyl (PCB) atropisomers, including PCB 95, PCB 149and PCB 132, was measured in 11 livers of harbour porpoises ( Phocoena phocoena ) from the southern NorthSea. Non-racemic enantiomeric ratios (ERs) were found in some samples. The value of ERs in three of the fourjuvenile porpoises was equal or almost equal to one, while the ERs in all adults differed from racemic andranged from 1.31 to 2.54 for PCB 95; from 1.19 to 1.81 for PCB 149 and from 0.45 to 0.94 for PCB 132. Therewere no relationships between the total concentration of PCBs and ERs. To understand the phenomena, therelationships between the ER value of individual chiral congener with age, concentration of total PCBs andPCB congener pattern were discussed. A model of intake and elimination kinetics was set up and it was testedusing the ratio between concentration of PCB 153 and PCB 101 in the liver samples. There was a clear trendbetween the enantiomeric ratios and the ratio between PCB 153 and PCB 101. Considering that PCB 153 is oneof the most persistent PCB congeners in marine mammals and PCB 101 is a relatively easy metabolisedcongener, this trend means that the enantiomeric ratio most likely reflects the proportion of the metabolisedcongener. The exposure period in contaminated conditions has a strong impact on ERs, and it is suggested thatERs in wildlife, combined with information on their anthropometric data, health status, diet and habitatconditions, might be good indicators of pollution in coastal ecosystems.
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