Sled Dogs Warn of Alaskan Mercury Levels

Sept. 7, 2007 — Alaskan sled dogs live in one of the world's most pristine environments, but a new study has revealed the hard-working canines are often exposed to potentially dangerous levels of mercury.

Since rural Alaskans frequently share food and living quarters with their dogs, the find — based on an analysis of the animals' fur — suggests mercury poisoning may also pose threats to many Arctic and subarctic region residents.

The study came after elder members of native communities expressed concern about the impact of mercury levels resulting from metal processing, coal burning and other industrial waste. Mercury especially accumulates in one food at the center of Yukon Territory diets — salmon.

"All the subsistence fed sled dogs in the Native Yukon villages were fed mostly salmon," said Kriya Dunlap, a champion sled dog racer and chemist at the University of Alaska Fairbanks.

Dunlap, who led the study, explained that dogs in the Alaskan phase of her study primarily ate salmon, supplemented with black bear, moose and caribou meat, along with table scraps. She also studied New York sled dogs that consumed a well-known commercial dog chow.

Dunlap and her team cut lower neck fur from 48 dogs, analyzing each sample for mercury content. As a control, the researchers also analyzed fur from 1,290-year-old dog feces found buried in the native village of Deering, located on the northern Seward Peninsula.

The findings have been accepted for publication in the journal Science of the Total Environment.

Mercury was highest in dogs living closer to river deltas, and mercury levels dropped incrementally with distance from these areas. Sled dog hair from Russian Mission, near Norton Sound on the Bering Sea, had the highest average mercury levels.

Dunlap said "spawning salmon act as contaminant pumps," since they can accumulate mercury from water, plants and prey. During migration, they stop eating and rely on stored fats and proteins, which can bind with mercury. The metabolism process may then rid salmon of mercury as the fish swim away from the delta.

The ancient samples and the dogs fed commercial chow showed much lower levels of mercury.

The health risks associated with mercury are debatable, but prior studies have linked mercury contamination to heart, lung, blood and immune system problems, especially in pregnant female mammals.

While Dunlap is "a proponent of subsistence diets for both dogs and humans," she said "the problem with the general populace formulating their own dog food is that these homemade diets are often unbalanced."

University of Alaska anthropologist Craig Gerlach told Discovery News that the new study "is really cutting-edge research."

Gerlach, however, added, "The exciting work is still to be done — looking at the implications of this model for human nutritional stress."

Eskimos and Native People of the North

The Natural Resources Defense Council

Dogsledding 101

The Arctic Council