Are liver and renal lesions in East Greenland polar bears (Ursus maritimus) associated with high mercury levels?
BACKGROUND
In the Arctic, polar bears (Ursus maritimus) bio-accumulate mercury as they prey on polluted ringed seals (Phoca hispida) and bearded seals (Erignathus barbatus). Studies have shown that polar bears from East Greenland are among the most mercury polluted species in the Arctic. It is unknown whether these levels are toxic to liver and kidney tissue.


METHODS
We investigated the histopathological impact from anthropogenic long-range transported mercury on East Greenland polar bear liver (n = 59) and kidney (n = 57) tissues.


RESULTS
Liver mercury levels ranged from 1.1-35.6 microg/g wet weight and renal levels ranged from 1-50 microg/g wet weight, of which 2 liver values and 9 kidney values were above known toxic threshold level of 30 microg/g wet weight in terrestrial mammals. Evaluated from age-correcting ANCOVA analyses, liver mercury levels were significantly higher in individuals with visible Ito cells (p < 0.02) and a similar trend was found for lipid granulomas (p = 0.07). Liver mercury levels were significantly lower in individuals with portal bile duct proliferation/fibrosis (p = 0.007) and a similar trend was found for proximal convoluted tubular hyalinisation in renal tissue (p = 0.07).


CONCLUSIONS
Based on these relationships and the nature of the chronic inflammation we conclude that the lesions were likely a result of recurrent infections and ageing but that long-term exposure to mercury could not be excluded as a co-factor. The information is important as it is likely that tropospheric mercury depletion events will continue to increase the concentrations of this toxic heavy metal in the Sub Arctic and Arctic marine food webs.
Sonne
Christian
C
Section for Contaminants, Effects and Marine Mammals, Department of Arctic Environment, National Environmental Research Institute, University of Aarhus, Frederiksborgvej, Roskilde, Denmark. csh@dmu.dk
Dietz
Rune
R
Leifsson
Pall S
PS
Asmund
Gert
G
Born
Erik W
EW
Kirkegaard
Maja
M
D000375:Aging; D000818:Animals; D001110:Arctic Regions; D004785:Environmental Pollutants / Q000009:adverse effects* / Q000032:analysis / Q000493:pharmacokinetics; D020387:Food Chain; D006116:Greenland; D007249:Inflammation; D007668:Kidney / Q000737:chemistry / Q000473:pathology*; D007674:Kidney Diseases / Q000209:etiology / Q000662:veterinary; D008099:Liver / Q000737:chemistry / Q000473:pathology*; D008107:Liver Diseases / Q000209:etiology / Q000662:veterinary; D008628:Mercury / Q000009:adverse effects* / Q000032:analysis / Q000493:pharmacokinetics; D014018:Tissue Distribution; D001503:Ursidae
D004785:Environmental Pollutants; D008628:Mercury