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Christian Sonne,^1,2 Rune Dietz,¹ Pall S. Leifsson,³ Erik W. Born,⁴ Robert J. Letcher,⁵ Maja Kirkegaard,¹ Derek C. G. Muir,⁶ Frank F. Riget,¹ and Lars Hyldstrup⁷

¹Department of Arctic Environment, National Environmental Research Institute, Roskilde, Denmark; ²Department of Veterinary Basic Sciences, and ³Department of Veterinary Pathobiology, Royal Veterinary and Agricultural University, Frederiksberg, Denmark; ⁴Greenland Institute of Natural Resources, Nuuk, Greenland; ⁵National Wildlife Research Centre, Canadian Wildlife Service, Environment Canada, Carleton University, Ottawa, Ontario, Canada; ⁶National Water Research Institute, Environment Canada, Burlington, Ontario, Canada; ⁷University Hospital of Hvidovre, Hvidovre, Denmark

Abstract
In East Greenland polar bears (Ursus maritimus) , anthropogenic organohalogen compounds (OHCs) (e.g., polychlorinated biphenyls, dichlorodiphenyltrichloroethane, and polybrominated diphenyl ethers) contributed to renal lesions and are believed to reduce bone mineral density. Because OHCs are also hepatotoxic, we investigated liver histology of 32 subadult, 24 adult female, and 23 adult male East Greenland polar bears sampled during 1999-2002. Light microscopic changes consisted of nuclear displacement from the normal central cytoplasmic location in parenchymal cells, mononuclear cell infiltrations (mainly portally and as lipid granulomas) , mild bile duct proliferation accompanied by fibrosis, and fat accumulation in hepatocytes and pluripotent Ito cells. Lipid accumulation in Ito cells and bile duct hyperplasia accompanied by portal fibrosis were correlated to age, whereas no changes were associated with either sex or season (summer vs. winter) . For adult females, hepatocytic intracellular fat increased significantly with concentrations of the sum of hexachlorocyclohexanes, as was the case for lipid granulomas and hexachlorobenzene in adult males. Based on these relationships and the nature of the chronic inflammation, we suggest that these findings were caused by aging and long-term exposure to OHCs. Therefore, these changes may be used as biomarkers for OHC exposure in wildlife and humans. To our knowledge, this is the first time liver histology has been evaluated in relation to OHC concentrations in a mammalian wildlife species, and the information is important to future polar bear conservation strategies and health assessments of humans relying on OHC-contaminated food resources. Key words: bile duct proliferation, chlordanes, dichlorodiphenyltrichloroethane, dieldrin, East Greenland, HCB, hexacyclohexanes, Ito cells, lipid granulomas, liver, mononuclear cell infiltrations, polar bear, polybrominated diphenyl ethers, polychlorinated biphenyls, portal fibrosis, DDT, HCH, PBDE, PCB, Ursus maritimus. Environ Health Perspect 113:1569-1574 (2005) . doi:10.1289/ehp.8038 available via http://dx.doi.org/ [Online 5 July 2005]

Address correspondence to C. Sonne, Arctic Wildlife Research Veterinarian, National Environmental Research Institute, Department of Arctic Environment, Frederiksborgvej 399, P.O. Box 358, DK-4000 Roskilde, Denmark. Telephone: 45-46-30-19-54. Fax: 45-46-30-19-14. E-mail: csh@dmu.dk

We thank H. Tuborg, B. Sandell, J. Brønlund, and local hunters for organizing sampling in East Greenland, and E. Heier for sharing digital images.

Financial support was provided by the Danish Cooperation for Environment in the Arctic, the Commission for Scientific Research in Greenland, and the Canada Research Chairs Program.

The authors declare they have no competing financial interests.

Received 24 February 2005 ; accepted 5 July 2005.

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