Arctic animals metabolize pesticides, limiting human exposure: study

New research reveals that Arctic mammals such as caribou can metabolize some current-use pesticides ingested in vegetation. (PHOTO COURTESY OF A. MORRIS)

Studies in recent years have warned Inuit that their traditional diet is tainted by industrial pollutants, absorbed into the tissues and organs of land and marine mammals they eat.

But at least one Arctic species appears to be processing some of those contaminants before the meat is consumed by humans.

New research from the University of Guelph shows that caribou can metabolize some current-use pesticides ingested from the vegetation they eat, meaning during digestion, they can limit the negative impact of those chemicals.

That’s reassuring considering the concentration of many pesticides — some of which are now banned — can become magnified in an animal that eats contaminated food.

The study basically suggests the natural process of metabolism limits chemical exposure in animals that consume caribou, including wolves and humans.

“This is good news for the wildlife and people of the Arctic who survive by hunting caribou and other animals,” said Adam Morris, a graduate student at the University of Guelph and lead author of the study that looked at the Bathurst caribou herd in the western Canadian Arctic.

“The lack of any significant biomagnification through the food chain indicates that there is very little risk of harm from exposure to these current-use pesticides in this region.”

Once pesticides enter rivers, lakes and vegetation, and are then consumed by other animals, the substances can become bio-magnified, Morris explained.

Small creatures consume the chemicals, bigger creatures eat those smaller ones and so by the time humans eat the larger animals, the level of chemicals has accumulated in the tissues, and especially the internal organs.

As part of their research, Morris, his colleagues and scientists with Environment Canada studied the vegetation-caribou-wolf food chain in the Bathurst region, where the persistence of other organic contaminants such as legacy pesticides — now banned — suggest that current pesticides might also be found.

The biomagnification of certain pesticides and other toxic chemicals used in industry, such as polychlorinated biphenyls or PCBs, has been noted in Inuit and other Aboriginal groups or northerners whose diets depend on hunting, Morris said.

But while many legacy pesticides are now widely banned under the Stockholm Convention, Morris said, few studies have looked at whether newer, current-use insecticides, herbicides and fungicides also accumulate in larger animals.

Researchers looked at caribou eating that vegetation and found that while pesticides were present in the vegetation, those compounds did not seem to accumulate in the caribou.

And the concentrations were even lower in wolves, suggesting both animals are metabolizing the pollutants.

“It is an important responsibility, both for health and for food security issues that northerners face, that we monitor traditional food sources,” Morris said, adding that the Bathurst caribou herd is critical to the region’s socio-economic security.

Morris acknowledged that current-use pesticides represent only a small percentage of contaminants in the Canadian Arctic.

“However, their unique set of properties does help us more clearly see how different contaminants behave in the environment and in food chains compared to legacy contaminants,” he said.

Morris is currently studying the marine food chain — including the chain that goes from seawater to algae, to plankton, to fish, and finally to seals.

Morris also said his research was only possible thanks to subsistence hunters and trappers who provided all the animal samples and traditional knowledge that were used in the study.

The study, titled Trophodynamics of current use pesticides and ecological relationships in the Bathurst region vegetation-caribou-wolf food chain of the Canadian Arctic was published in a recent issue of the journal Environmental Toxicology and Chemistry.