From August 24, 2005
Canadian
Grizzlies Contaminated with Pesticides Due to Salmon Diet
(Beyond Pesticides, August 24, 2005) A recent
study of grizzly bears in British Columbia has shown a link between
high presence of pesticides and a salmon diet. Researchers in Canada
published a report that found that salmon consumed by coastal grizzly
bears were responsible for 70 percent of all organochlorine pesticides,
85 per cent of the polybrominated diphenyl ethers (PBDEs), and 90 percent
of the PCBs present in the bears.
The study compared fat and hair samples from coastal and inland bears. Coastal grizzly bears have a diet rich in salmon; consuming spawning salmon almost exclusively between the late summer and the fall. Inland bears, in contrast, subsist on a completely salmon free diet. The results of the study showed significantly higher levels of pesticides and other toxins in the coastal bears.
The coastal grizzly bears showed levels of chemicals in one gram of fat that were as high, in some cases, as 20 parts per billion (ppb) of DDT, 43 ppb for PCBs, and 53 ppb for PBDEs. While the grizzly bears are not as severely contaminated as other salmon-eating animals including polar bears and orcas, scientists do raise concern that the high levels of pesticides will have an effect on the reproductive abilities of young females.
The report noted that, due to the fact that some of the pesticides found in the fat samples were endocrine disruptors combined with the low reproductive rates and cyclical hibernation of bears, “adult female grizzly bears may supply elevated concentrations of endocrine-disrupting chemicals to their young.”
Salmon contamination
in the Pacific Northwest has long been
recognized as a problem with several campaigns to regulate and protect
the wild salmon. Yet even with national regulations curbing pesticide
practices that prove fatal to salmon, the North Pacific remains a threat.
“The North Pacific is a sink for these contaminants, which are
probably introduced through the atmosphere . . . from Asia. It reminds
us once again that our planet is a small one,” commented Dr. Peter
Ross, one of the co-authors of the report published about the study
(source: The
Globe and Mail).