Contaminant Project Coordinator - Misty MacDuffee
Coastal grizzlies can’t hide from global or local pollutants
The legacy of Persistent Organic Pollutants like DDT, PCBs and organo-chlorine pesticides continues to haunt both industrialized and remote regions of the planet. Despite a ban on producing many of these chemicals in North America, many of them continue to be used in Asia. There, they are released into the atmosphere, travel over the Pacific, deposit into the open Pacific Ocean, and accumulate through the marine food chain all the way to coastal North America.As a result, top marine predators like killer whales and polar bears have dubious distinctions as heavily contaminated animals.
If these predators are at risk, what about terrestrial predators that feed on the marine food web? Could coastal grizzly bears be exposed to Persistent Organic Pollutants as a consequence of their reliance on Pacific salmon?
Research
To answer this question Raincoast teamed up with wildlife toxicologist Dr. Peter Ross at the Institute of Ocean Sciences and Jennie Christensen at the University of Victoria. Our first task was to determine the level of contaminants within BC grizzlies and second, to see if there was a connection to diet.
By measuring contaminants within the tissue of the bears, and using stable isotopes in the hair to understand diet, our results clearly showed that pollutant concentrations in grizzly bears reflects their consumption of Pacific salmon. In fact, salmon are responsible for most of the contaminants within the grizzlies, and the greater the dependence on salmon, the higher the contaminant levels were. The good news is that compared to other top marine predators like killer whales, the level of POPs in grizzlies is relatively low. Exactly how low level concentrations effect grizzlies, especially at important developmental stages, is unknown.
Brominated Flame Retardants
Of new concern however, was the presence of a pollutant group not considered a “legacy” chemical. It was a class of “emergent” chemicals called PBDEs or “brominated flame retardants” which are produced and used with fervor in North America. These unregulated PBDEs also act as hormone mimics in the body and were found in non-salmon-eating “interior” grizzlies in relatively high concentrations. The concentrations in grizzlies exceeded those found in Swedish women’s breast milk, levels which led to the ban of two of the three commercial PBDE products in Europe. These findings were published in 2005.
The Hibernation hangover
In 2007, we published the second paper in this study, which focused on the question “what happens to these chemicals during hibernation when the bear’s fat is burned-off”? Our study found that generally, pollutants in the bear’s body become concentrated as this energy source is utilized during the winter. Elevated concentrations of contaminants and metabolic products may be passed on to newborn cubs through consumption of their mother’s milk.
This study also made important findings on brominated flame-retardants. These concerns were expressed in a letter to Environment Canada in 2007.
Scientific Papers:
- Persistent Organic Pollutant exposure in BC grizzlies: the consequence of divergent diets (2005)
- Hibernation associated changes in persistent organic pollutants (POP) levels and patterns in British Columbia grizzly bears (2007)
Media Articles:
- Poison feast of salmon contaminates B.C. grizzlies (Globe and Mail August 5th, 2005)
- B.C. Grizzlies Show Signs of Pollution From Asia: Chemicals Banned in Canada turn up in Salmon (Vancouver Sun March 3, 2007)
- How Environment Canada is Shirking Its Duty to Protect Wildlife (and People) from Flame Retardants (Counterpunch Dec 14, 2007)
Letters and Reports:
