|Norway's Polar Bears Suspected Victims of PCB Contamination|
Researchers in Norway’s Svalbard Islands have found developmental deformities in seven polar bears, according to a July report in the Journal of Wildlife Diseases. Each of the bears had both male and female reproductive organs. All seven bears are genetic females, and some have had cubs, but each has a small penis in front of its vagina. Hermaphrodites do occur in nature, but these seven are part of a population of some 450 bears surveyed, an unusually high rate. Although the cause is not known for certain, researchers suspect polychlorinated biphenyls (PCBs) may be the culprit.
PCBs are among many pollutants that circulate the globe in the atmosphere. Recent arctic and antarctic research has shown both that atmospheric circulation tends to concentrate pollutants near the poles, and that the cold polar temperatures condense airborne pollutants. Condensed PCBs, heavy metals, pesticides, and other contaminants fall to the surface, where they enter the food chain. Polar bears eat seals, whose fat stores toxins accumulated from arctic fish. PCBs, pesticides, and other compounds concentrated in bears’ bodies could interfere with normal fetal development. Laboratory studies have shown that PCBs can interfere with sexual development in mammals. PCBs are therefore considered a likely cause of the Svalbard hermaphroditic bears, although the link is not yet proven.
The bears were discovered by zoologists from the Polar Institute in Tromso, Norway and the University of Oslo during a project to monitor the health and population dynamics of Norway’s polar bear population. The zoologists hope that this study will encourage similar monitoring of arctic carnivores elsewhere. Polar bears also live in arctic coastal areas of Canada, Alaska, and Russia.
In similar but separate research, unusually high levels of PCBs in body fat and breast milk among human populations in the Arctic. Like bears, native peoples living in the region rely on fish as an important dietary component .
To read more, see
Environmental Science, A Global Concern,
Cunningham and Saigo, 5th ed.
Environmental Science, Enger and Smith,
For further information, see these related web sites:
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