Enantiomer-Specific Accumulation of PCB Atropisomers in the Bowhead Whale (Balaena mysticetus)

Abstract

Blubber (n = 40) and liver (n = 20) samples from the bowhead whale (Balaena mysticetus) were collected during the 1997-1998 Native (Inuit) subsistence harvests in Barrow, AK. Bowhead tissues and zooplankton were analyzed for polychlorinated biphenyl (PCB) concentrations and the enantiomeric fractions (EFs) of eight chiral PCB congeners (PCB-91, 95, 135, 136, 149, 174, 176, and 183) to quantify the enantiomer-specific accumulation of PCBs in this cetacean. PCB concentrations in bowhead blubber were low (mean +/- 1 SE: 610 +/- 54 ng g(-1) lipid) relative to other cetaceans. The accumulation of several chiral PCBs (PCB-91, 135, 149, 174, 176, and 183) in bowhead blubber was enantiomer-specific relative to bowhead liver and zooplankton, suggesting that biotransformation processes within the bowhead whale are enantioselective. The EFs for PCB-95 and 149 were significantly correlated with body length in male and female whales, while EFs for PCB-91 correlated with length in males only. Despite evidence for enantioselective biotransformation, all three congeners bioaccumulated in the bowhead relative to PCB-153. Results suggest that enantioselective accumulation of PCB-91, 95, and 149 is influenced by PCB concentrations, age, and/or the modification of an uncharacterized stereoselective process (or processes) during sexual maturity.

Chirality as an Environmental Forensics Tool

“…A number of aquatic invertebrates do appear incapable of biotransforming chiral POPs. The copepod Calanus hyperboreus has almost always been observed with racemic proportions of a-HCH, cis-and trans-chlordane, heptachlor epoxide, oxychlordane, MC-5, and PCBs [189][190][191][192], consistent with this hypothesis. While a-HCH in most Northwater Polynya pelagic and benthic invertebrates, including Calanus, were nonracemic (EF range of 0.41 to 0.43), these EFs were very similar to that in Polynya waters (EF ¼ 0.45) [137].…”

“…Characterization of enantiomer composition in the food web demonstrated enantioselective detoxification of POPs, including PCBs, in cetaceans. In the Bering-ChukchiBeaufort Sea area, bowhead whales (Balaena mysticetus) had nonracemic amounts of some chiral PCBs, while their Calanus zooplankton prey had racemic levels [189]. Given the simplicity of the bowhead whale food chain, these observations indicate that these cetaceans had biotransformed PCB atropisomers enantioselectively.…”

“…The EFs of PCB 91 were significantly correlated with body length in males only, while those of PCBs 95 and 149 were correlated with lengths for both sexes. Bioaccumulation of these three congeners was influenced by sex, age, and PCB concentration [189]. Likewise, shifts in EFs for a-HCH between Calanus and the livers and blubber of bowhead whales suggested some capacity for degradation of this analyte [190].…”

Distribution of Chiral PCBs in Selected Tissues in the Laboratory Rat

“…From a human health point of view, the enantiomeric enrichment of several chiral PCBs (PCB 91, 95, 135, 149, 174, 176, and 183) found in samples of blubber from bowhead whales is of particular interest (12), because this blubber is a part of the diet of Inuit people in northern Canada. Thus, humans can be exposed to enantiomerically enriched PCBs mixtures via the diet.…”

Chiral xenobiotics bioaccumulations and environmental health prospectives

“…These results contributed to the quality assurance/ quality control approaches using SRMs for chiral environmental chemistry. Hoekstra et al (2002) studied blubber and liver samples collected from the bowhead whale (Balaena mysticetus) in Canada. The authors detected chiral PCB congeners 91, 95, 135, 136, 149, 174, 176, and 183 in these samples.…”