Heavy metals and essential elements in livers of the polar bear (Ursus maritimus) in the Canadian Arctic.

Polar bear (Ursus maritimus) livers (67) from six Management Zones in the western and central Canadian Arctic were analysed for 22 elements. Several, Ba, Be, Co, Mo, Ti, V and Zr, were near the detection limit in all cases. Baseline data were obtained for the remaining elements, Ag, As, Ca, Cd, Cu, Fe, Hg, K, Mg, Mn, Na, P, Se, Sr and Zn. No statistically significant effect of age, sex or geographical location was found for any of the elements, except Cd, Hg and Se, for which age and geographical location effects were found. The frequency distribution of Zn levels was bimodal. The second peak in the distribution appeared to be related to elevated levels of Cu. The average level of Cu was 104 mg kg-1 (dry wt.), higher than other marine mammals. Average levels of Cd were significantly higher in the eastern zones, but were always less than 1.0 mg kg-1 (dry wt.), significantly lower than their prey species. This may be due to the preference of polar bears for eating seal skin and fat which is low in Cd. Mercury levels tended to be higher in the western zones bordering the Beaufort Sea, which may be related to a higher proportion of bearded seal in their diet. Mean Hg levels ranged from 20 mg kg-1 in the eastern zones were related to age by the expression: Hg (mg kg-1 dry wt.) = 15.7 + 8.0 Age (years). Mercury levels in the most northerly zone near Melville Island were very high: Hg (mg kg-1 dry wt.) = 18.4 + 27.5 Age (years). Levels of Hg and Se were very highly correlated, with a molar ratio of 1.27:1, Hg/Se.