Alaskan sled dog fur helps scientists detect mercury

BEIJING, March 25 (Xinhuanet) -- The thick fur of a sled dog does more than keep the canine warm, it collects mercury, which scientists say can be used to detect contamination in the environment, and maybe in humans.

"The foods sled dogs are eating scraps left over from people in the villages," said Peter Bowers, an archaeologist at Northern Land Use Research, an Alaskan consulting firm, who contributed to a study published in the journal Science of the Total Environment in October.

Because a sled dog's fish diet is similar to what Alaska's indigenous population eats, scientists think it can provide information about how much mercury humans are eating, and where the toxin enters the food chain. Mercury levels in fish change depending on their location and feeding habits, and testing dog hair from different husky populations that eat those fish shows scientists the areas of high mercury.

The researchers analyzed hair from huskies in five regions of Alaska; they also analyzed a sample from sled dog remains dating back to 780 A.D. Of the present-day dogs feasting on salmon, those from Russian Mission, Alaska ¢w a village near the Bering Sea ¢w had the most mercury, topping out at more than a third of the toxic level. Hair samples taken from dogs at Fort Yukon, 800 miles from the sea, had the lowest mercury levels, which were not significantly different from the control group. In contrast, archaeological samples had roughly half the mercury of the lowest modern-day sample.

"The levels of [present-day] mercury decreased as you go up the Yukon and away from the mouth of the Bering Sea," said Kriya Dunlap, the lead author of the study and a chemist at the University of Alaska, plus a championship sled dog racer to boot. According to Dunlap, salmon fast when they move inland.

Salmon become contaminated from eating plankton and algae tainted with mercury from pollution. They have difficulty metabolizing the toxin, so it builds up in their systems and gets passed on to anything that eats them ¢w including sled dogs and people. Dogs with more mercury were found closer to the sea where the salmon feed.

"It makes sense because the salmon aren't eating [further inland]," Dunlap said. Mercury accumulates in fats and proteins, and when the fish aren't eating, they burn off those same fats and proteins for energy. This helps to eliminate the toxin, and may be why fasting fish have less mercury.

Sled dog fur is not the only mechanism to measure mercury. Scientists can also study mercury levels in human and animal organs, blood, breath and hair. Mercury gets into hair through the blood that follicles need to grow hair. Scientists have used hair to test for minerals for about 75 years.

(Agencies)