Determination of HCHs, PCBs, and DDTs in brain tissues of marine mammals off different age

Abstract

The concentrations of a number of polychlorinated biphenyls and chlorinated pesticides in brain tissues of marine mammals of different age and regional origin were determined by using high-resolution capillary gas chromatography and electron capture detection. Brain tissues of two neonatal and three stillborn northern fur seals (Callorhinus ursinus) collected in the Bering Sea, Pacific Ocean, were examined. In addition, cerebrum, cerebellum, and hypothalamus of one adult female common dolphin (Delphinus delphis) stranded on the coast of Massachusetts, Atlantic Ocean, were examined. It showed clearly that α-HCH was dominant in all brain tissues (90–203 ng/g extractable lipids) compared with other tissues like liver or blubber (45–61 ng/g extractable lipids). This excess of α-HCH in brain tissue was due to only one enantiomer, (+)-α-HCH, whereas in other tissues both enantiomers contributed to the α-HCH concentration. Comparing the overall general xenobiotic burden, the HCH isomers (99–216 ng/g extractable lipids) resemble the PCB (17–105 ng/g extractable lipids) and DDT (111–171 ng/g extractable lipids) levels in brain tissues. The latter two groups exceed the HCHs in liver tissue and in blubber. On a single compound basis, the highest levels are found in brain for α-HCH (fur seal pups: 90–203 ng/g extractable lipids, adult dolphin: 221–305 ng/g extractable lipids), 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB153) (fur seal pups: 4–25 ng/g extractable lipids, adult dolphin: 260–377 ng/g extractable lipids) and 4,4′-DDE (fur seal pups: 104–164 ng/g extractable lipids, adult dolphin: 364–625 ng/g extractable lipids). The levels of α-HCH and 4,4′-DDE are comparable. No significant difference concerning the xenobiotic burden between neonatal and stillborn northern fur seals could be seen in contrast to the higher concentrations of the adult common dolphin. The patterns of some xenobiotics in the samples were compared with each other by using statistical methods like the similarity index and the principal component analysis (PCA).