Methylsulfone polychlorinated biphenyl and 2,2-bis(chlorophenyl)-1,1-dichloroethylene metabolites in beluga whale (Delphinapterus leucas) from the St. Lawrence River estuary and western Hudson Bay, Canada

Knowledge is limited regarding methylsulfone (MeSO2)-polychlorinated biphen yl (PCB), and especially MeSO2-2,2-bis(chlorophenyl)-1,1-dichloroethylene ( DDE), metabolites in cetacean species. We hypothesized that the ability of beluga whale (Delphinapterus leucas) to biotransform PCB and DDE compounds, and to form and degrade their MeSO2-PCB and -DDE metabolites, is related t o the capacity for xenobiotic metabolism. Adipose biopsies were collected f rom male and female beluga whale From distinct populations in the St. Lawre nce River estuary (STL) and western Hudson Bay (WHB), Canada, which are con trasted by the exposure to different levels of cytochrome P450 enzyme-induc ing, chlorinated hydrocarbon contaminants. The PCBs, DDTs, DDEs, 28 MeSO2 m etabolites of 14 meta-para chlorine-unsubstituted PCBs, and four MeSO2 meta bolites of 4,4'- and 2,4'-DDE were determined. The mean concentrations of t otal (Sigma-) MeSO2-PCB in male STL beluga (230 ng/g), and ratios of Sigma- MeSO2-PCB to Sigma-PCB (0.05) and Sigma-precursor-PCB (0.17) were approxima tely twofold higher, whereas the Sigma-precursor-PCB to Sigma-PCB ratio was approximately twofold lower, than in male WHB beluga. Both populations had a low formation capacity for MeSO2-PCBs with greater than or equal to six chlorines (<4% of Sigma-MeSO2 PCBs). The congener patterns were dominated b y trichloro- and tetrachloro-MeSO2-PCBs, and tetrachloro- and pentachloro-M eSO2-PCBs in WHB and STL animals, respectively. In addition to 2- and 3-MeS O2-4,4'-DDE, two unknown MeSO2-2,4'-DDEs were detected. The mean 3-MeSO2-4, 4'-DDE concentration in STL beluga (1.2 ng/g) was much greater than in WHB (<0.01 ng/g) animals. The concentrations of 4,4'-DDE, and not 3-MeSO2-4,4'- DDE, increased with age in male STL animals. We demonstrated that sulfone f ormation and clearance is related to metabolic capacity, and thus PCB, DDE, and MeSO2-PCB and -DDE toxicokinetics differ for STL and WHB beluga. In th e past, the capacity of odontocetes for PCB and DDE biotransformation leadi ng to persistent sulfone metabolites has been underestimated. More informat ion is needed for other cetacean species and marine mammals. The results of this study indicate that MeSO2-PCBs and -DDEs need to be included in the t oxicologic risk assessment of PCB and DDT exposure in odontocetes, and perh aps for cetaceans in general.