Overview and regional and temporal differences of heavy metals in Arctic whales and ringed seals in the Canadian Arctic

Concentrations of mercury, cadmium, and other heavy metals in tissues of belugas (Delphinapterus leucas), narwhal (Monodon monoceros) and ringed seals (Phoca hispida) from across the Canadian Arctic are reported. Published and new information is used to provide an overview of metals in tissues of these animals, to delineate the existence of a spatial trend of mercury and cadmium in belugas and ringed seals, and to show a temporal trend is superimposed on the geochemical trend. Mercury concentrations in tissues of Arctic whales and ringed seals were high relative to the Canadian guideline of 0.5 μg/g wet wt., for mercury in fish, except in the skin of belugas (0.59-0.78 μg/g wet wt.) and flesh of ringed seals (0.39-0.41 μg/g wet wt.). In the flesh of belugas (0.94-1.34 μg/g wet wt.), and in the liver of ringed scals, tissues that are also consumed by Native people in the Arctic (8.34-27.5 μg/g wet wt.), the guideline value was significantly exceeded. Mean lead concentrations in tissues of belugas, narwhal and ringed seals were generally low (0.002-0.028 μg/g wet wt.), except in tissues of belugas in the St. Lawrence River (0.10-0.15 μg/g wet wt.). The concentration of zine in the skin of whales was two to three times higher than in other tissues. The concentration of cadmium in organs was highest in narwhal. There was a positive correlation between mercury and selenium in the liver of all three species. The concentration of mercury in tissues of belugas and ringed seals was higher in the western than the eastern Arctic. This was attributed to different natural background concentrations in the western and eastern Arctic of Canada dictated by different geological formations in the two regions. Cadmium concentrations in tissues of belugas and ringed seals were higher in the eastern than the western Arctic. Zinc and copper in some tissues of belugas and ringed seals were also higher in the eastern than the western Arctic. Mercury in the liver of belugas was found to have increased in the western and eastern Arctic over 10–12 years. Mercury in the liver of ringed seals in the western Arctic and narwhal in the eastern Arctic showed similar increases. In recently collected belugas, the rate of accumulation of mercury in the liver was approximately twice that in belugas collected 10–12 years ago. In ringed seals, the rate was three times higher in recent samples compared to 15–20 years ago. There was no temporal change in cadmium levels in tissues of belugas, ringed seals or narwhal.