5 THINGS: TOXINS IN POLAR BEARS.

1 PERSISTENT ORGANIC POLLUTANTS

Biologists have long known that polar bears and other arctic animals carry toxic chemicals known as persistent organic pollutants (POPs) in their bodies. Those chemicals, which include such substances as PCBs, damage immune, digestive and reproductive systems. Now new tests have found a wide range of undiscovered contaminants in polar bears around Hudson Bay.

2 210 FOUND

Environment Canada researcher Robert Letcher and his colleagues tested for 295 POPs. They found a total of 210 “with some frequency” in fat and liver samples collected from 41 bears that had been harvested in 2013-14 from the shores of Hudson Bay.

3 LEVELS VARY WIDELY

The levels of contamination varied widely among the chemicals. Most were found in the range of parts per billion. Some, such as one chemical used as a water repellent for fabrics, were approaching parts per million.

4 WIDESPREAD

Some of the contaminants such as PCBs and DDT were restricted under the 2001 Stockholm Convention and have long been in decline. Levels of flameretardant chemicals, added to the Stockholm list in 2009, also seem to be dropping. But others don’t seem to be declining at all. The fact they’ve been found in a top-of-the-food-web predator like polar bears suggest they’re widespread, Letcher said. “If a compound can migrate its way through the food web, all the way up to the polar bear, it must be pretty extensive.”

5 CLIMATE CHANGE

Understanding the impact of the chemicals is complicated by the context of Arctic climate change, said Letcher. “If there’s any stressing factor to life in the Arctic, it is climate change. It’s a major challenge for us to understand how climate change variables are affecting contaminant exposure.”