Letcher Robert J, Gebbink Wouter A, Sonne Christian, Born Erik W, McKinney Melissa A, Dietz Rune
Wildlife and Landscape Science Directorate, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Ottawa, Ontario, Canada.
Environ Int. 2009 Nov;35(8):1118-24. doi: 10.1016/j.envint.2009.07.006. Epub 2009 Aug 15.
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 (MeSO(2)-) 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-MeSO(2)-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 SigmaPCBs, p,p'-DDE, SigmaCHLs, SigmaMeSO(2)-PCBs, 3-MeSO(2)-p,p'-DDE, PCP, SigmaPBDEs, total-(alpha)-HBCD, SigmaOH-PBDEs, SigmaMeO-PBDEs and SigmaOH-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 <or=1 in the brain, with the exception of SigmaOH-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.
我们报告了东格陵兰环斑海豹（Pusa hispida）脂肪中各类持久性氯化和溴化污染物及其代谢副产物：多氯联苯（PCBs）、氯丹（CHLs）、羟基（OH-）和甲基磺酰基（MeSO₂-）PCBs、多溴联苯（PBBs）、OH-PBBs、多溴二苯醚（PBDE）和六溴环十二烷（HBCD）阻燃剂以及OH-和甲氧基（MeO-）PBDEs、2,2-二氯-双（4-氯苯基）乙烯（p,p'-DDE）、3-MeSO₂-p,p'-DDE、五氯苯酚（PCP）和4-羟基-七氯苯乙烯（4-OH-HpCS），向北极熊（Ursus maritimus）组织（脂肪、肝脏和大脑）的比较生物累积、生物转化和/或生物放大情况。我们在东格陵兰熊的主要食物——环斑海豹脂肪中高频检测到了所有研究的污染物，但OH-PCBs和4-OH-HpCS除外，这表明这些酚类污染物可能源于代谢，分别是北极熊体内累积的PCBs和八氯苯乙烯（OCS）形成的，而非从海豹脂肪饮食中生物累积而来。对于所有可检测的类别总和或单个有机卤化物，一般而言，环斑海豹到北极熊的多氯联苯、p,p'-DDE、总氯丹、总甲基磺酰基PCBs、3-MeSO₂-p,p'-DDE、PCP、总多溴二苯醚、总α-六溴环十二烷、总羟基多溴二苯醚（OH-PBDEs）、总甲氧基多溴二苯醚（MeO-PBDEs）和总羟基多溴联苯（OH-PBBs）的平均生物放大系数（BMFs）表明这些有机卤化物会生物累积，在某些情况下还存在组织特异性生物放大，例如熊脂肪和肝脏的BMFs范围为2至570。血脑屏障似乎能有效减少大脑中的累积，因为大脑中的BMFs≤1，但总羟基多溴联苯除外（平均BMF = 93±54）。与OH-PCB代谢物不同。熊组织中的OH-PBDEs似乎主要是从海豹脂肪中累积而来，而非由熊体内的PBDEs代谢形成。使用北极熊肝微粒体进行的体外多溴二苯醚消耗试验表明，多溴二苯醚同系物氧化代谢的速率非常缓慢，这支持了熊组织中OH-PBDEs的主要来源是从海豹累积而来的可能性。我们的研究结果表明，从环斑海豹到北极熊，有机卤化物的生物转化、生物累积和/或生物放大差异很大，且取决于所讨论的污染物。我们的结果表明，饮食中生物累积以及在某些情况下生物放大的氯化和溴化污染物及/或代谢物的复杂性不断增加，这可能是导致东格陵兰北极熊健康问题的一个压力因素。
