Mercury Levels On The Rise In Polar Bears

Mercury levels have increased steadily in Northwestern Greenland's polar bears in the past century, according to a new study, mainly due to industrial sources such as coal burning and iron smelting (Environ. Sci. Technol., DOI: 10.1021/es1028734). The neurotoxic metal travels through the atmosphere to the Arctic, where researchers have shown that it accumulates at the top of the food web in humans and polar bears.

The new study extends a previously published record of mercury levels in the region's bears from 1920 to 1990 (Environ. Sci. Technol., DOI: 10.1021/es051636z). Rune Dietz of Aarhus University in Denmark, and colleagues filled in data gaps in their previous study by testing hair from polar bears hunted by the local Inuit community from 1990 to 2008. They also analyzed specimens stored at Denmark's National Museum, to extend the record back to 1892.

Based on samples from 117 bears, representing 28 different years over those 12 decades, the researchers calculated that mercury levels in the region's polar bears had increased by about 1.6% annually. Using polar bear hair found in the region dating from 1300, the researchers determined the natural background levels of mercury and compared them to those in the contemporary bears. The team concludes that more than 95% of the mercury in today's bears comes from anthropogenic emissions.