(Table 1) Neutral and phenolic organohalogen compounds in blubber samples of ringed seals (Pusa hispida) from East Greenland

We report on the comparative bioaccumulation, biotransformation and/or biomagnification from East Greenland ringed seal (Pusa hispida) blubber to polar bear (Ursus maritimus) tissues (adipose, liver and brain) of various classes and congeners of persistent chlorinated and brominated contaminants and metabolic by-products: polychlorinated biphenyls (PCBs), chlordanes (CHLs), hydroxyl (OH-) and methylsulfonyl (MeSO2-) PCBs, polybrominated biphenyls (PBBs), OH-PBBs, polybrominated diphenyl ether (PBDE) and hexabromocyclododecane (HBCD) flame retardants and OH- and methoxyl (MeO-) PBDEs, 2,2-dichloro-bis(4-chlorophenyl)ethene (p,p'-DDE), 3-MeSO2-p,p'-DDE, pentachlorophenol (PCP) and 4-OH-heptachlorostyrene (4-OH-HpCS). We detected all of the investigated contaminants in ringed seal blubber with high frequency, the main diet of East Greenland bears, with the exception of OH-PCBs and 4-OH-HpCS, which indicated that these phenolic contaminants were likely of metabolic origin and formed in the bears from accumulated PCBs and octachlorostyrene (OCS), respectively, rather than being bioaccumulated from a seal blubber diet. For all of the detectable sum of classes or individual organohalogens, in general, the ringed seal to polar bear mean BMFs for SumPCBs, p,p'-DDE, SumCHLs, SumMeSO2-PCBs, 3-MeSO2-p,p'-DDE, PCP, SumPBDEs, total-(alpha)-HBCD, SumOH-PBDEs, SumMeO-PBDEs and SumOH-PBBs indicated that these organohalogens bioaccumulate, and in some cases there was tissue-specific biomagnification, e.g., BMFs for bear adipose and liver ranged from 2 to 570. The blood-brain barrier appeared to be effective in minimizing brain accumulation as BMFs were <= 1 in the brain, with the exception of SumOH-PBBs (mean BMF = 93±54). Unlike OH-PCB metabolites, OH-PBDEs in the bear tissues appeared to be mainly accumulated from the seal blubber rather than being metabolic formed from PBDEs in the bears. In vitro PBDE depletion assays using polar bear hepatic microsomes, wherein the rate of oxidative metabolism of PBDE congeners was very slow, supported the probability that accumulation from seals is the main source of OH-PBDEs in the bear tissues. Our findings demonstrated from ringed seal to polar bears that organohalogen biotransformation, bioaccumulation and/or biomagnification varied widely and depended on the contaminant in question. Our results show the increasing complexity of bioaccumulated and in some cases biomagnified, chlorinated and brominated contaminants and/or metabolites from the diet may be a contributing stress factor in the health of East Greenland polar bears.本研究报道了持久性氯代、溴代污染物及代谢副产物的不同类别与同系物，从东格陵兰环斑海豹（Pusa hispida）鲸脂到北极熊（Ursus maritimus）脂肪、肝脏与脑组织的比较生物富集、生物转化及/或生物放大效应。所涉污染物包括：多氯联苯（polychlorinated biphenyls, PCBs）、氯丹类（chlordanes, CHLs）、羟基（hydroxyl, OH-）与甲基磺酰基（methylsulfonyl, MeSO2-）取代多氯联苯、多溴联苯（polybrominated biphenyls, PBBs）、羟基多溴联苯（OH-PBBs）、多溴二苯醚（polybrominated diphenyl ether, PBDE）及六溴环十二烷（hexabromocyclododecane, HBCD）阻燃剂，以及羟基（OH-）与甲氧基（methoxyl, MeO-）取代多溴二苯醚、2,2-二(4-氯苯基)二氯乙烯（p,p'-DDE）、3-甲基磺酰基-p,p'-DDE、五氯苯酚（pentachlorophenol, PCP）与4-羟基七氯苯乙烯（4-OH-HpCS）。本研究在作为东格陵兰北极熊主要食物来源的环斑海豹鲸脂中，高频检出了所有目标污染物，但羟基多氯联苯与4-羟基七氯苯乙烯除外；这表明此类酚类污染物大概率源自代谢过程，分别由北极熊体内蓄积的多氯联苯与八氯苯乙烯（octachlorostyrene, OCS）转化生成，而非通过捕食海豹鲸脂的食物链直接生物富集获得。针对所有可检出的类别总和或单个有机卤代物，总体而言，环斑海豹到北极熊的总多氯联苯（SumPCBs）、p,p'-DDE、总氯丹类（SumCHLs）、总甲基磺酰基多氯联苯（SumMeSO2-PCBs）、3-甲基磺酰基-p,p'-DDE、PCP、总多溴二苯醚（SumPBDEs）、总α-HBCD（total-(alpha)-HBCD）、总羟基多溴二苯醚（SumOH-PBDEs）、总甲氧基多溴二苯醚（SumMeO-PBDEs）与总羟基多溴联苯（SumOH-PBBs）的平均生物放大因子（BMF）表明，此类有机卤代物可发生生物富集，部分还存在组织特异性的生物放大效应，例如北极熊脂肪与肝脏组织的BMF值介于2至570之间。血脑屏障（blood-brain barrier）似乎可有效抑制脑组织的污染物蓄积，北极熊脑组织的BMF值均≤1，仅总羟基多溴联苯（SumOH-PBBs）除外，其平均BMF为93±54。与羟基多氯联苯代谢物不同，北极熊组织中的羟基多溴二苯醚主要通过捕食海豹鲸脂获得，而非由北极熊体内的多溴二苯醚代谢生成。本研究采用北极熊肝微粒体开展的体外多溴二苯醚耗竭实验结果显示，多溴二苯醚同系物的氧化代谢速率极慢，这进一步佐证了“北极熊组织中的羟基多溴二苯醚主要来源于海豹鲸脂的直接蓄积”这一推论。本研究结果表明，从环斑海豹到北极熊的有机卤代物生物转化、生物富集及/或生物放大效应存在显著差异，且具体取决于污染物种类。本研究结果显示，通过食物链生物富集（部分还发生生物放大）的氯代、溴代污染物及其代谢物的复杂性日益提升，这可能是影响东格陵兰北极熊健康的潜在胁迫因素之一。