Bears take brunt of toxic chemicals as ban looms
Date: 22-May-01
Country: SWEDEN
Author: Alister Doyle
The 12 so-called persistent organic pollutants (POPs) are found in pesticides or industrial waste and can cause potentially fatal cancers and birth defects in both humans and animals.
POPs have a propensity to accumulate in fatty tissue, sometimes rising to 70,000 times natural levels.
Polar bears are among the most susceptible animals because of their high-fat diets - given the choice, a polar bear will gorge on the fat of a seal and dump the meat, building its fat reserves to get through the winter.
More than 120 nations will formally agree a treaty in Stockholm on Tuesday to outlaw or minimise use of the "dirty dozen" POPs - found in pesticides to kill termites, in fire retardants in homes, in electric transformers and as additives in paint or plastics.
But it may take the 25-year lifespan of a polar bear before the existing chemicals break down in the Arctic, which receives POPs from wind and sea currents.
"Polar bears pick up almost all the POPs that make it to the Arctic," said Andrew Derocher, a research scientist at the Norwegian Polar Institute who helps tag about 100-120 bears a season to study the impact of pollution.
"We're seeing most of the effects in hormone regulation, and also looking at the effects in the immune system...There are negative effects of PCBs (polychlorinated biphenyls) in particular on polar bears."
He said it was too early to say whether the bear population was falling. Other factors, such as a warming climate which has thinned the Arctic icecap, also threaten the bears' lifestyle.
A worrying sign is a pseudo-hermaphroditism among the bears. An unusually high 1.5 percent of females have an extended clitoris that looks like a male penis.
"It seems that females in this state are capable of reproducing. But it's a possible indicator of endocrine disruption, and that could be caused by pollution," Derocher said. The abnormality was not found in the Canadian Arctic.
He estimated that there were 2,500 to 3,000 polar bears from Svalbard, east of Norway, to Franz Josef Land, north of Russia.
Polar bears give birth in December to one or two cubs, which weigh about 700 grams (1.5 lb) - about the size of a guinea pig. The fat-rich milk they drink to grow is already polluted.
Derocher said there were some signs that PCBs might be on the decline in the Arctic, but traces of some other chemicals were rising.
