The concentration of mercury in Arctic fish is much lower than expected, according to new research, and the Soviet Union, or lack thereof, may have something to do with it.

A team of American, Russian and Canadian scientists has discovered "that the economic decline of the former Soviet Union, which collapsed in 1991, appears to have been good for the Arctic environment in that part of the world," Leandro Castello, an assistant professor of fish and wildlife conservation in the College of Natural Resources and Environment at Virginia Tech, said in a statement.

According to a United Nation's environmental study, a good deal of atmospheric mercury comes from mining and ore processing, such as smeltering. Then, under certain water conditions, mercury changes into a form that can be absorbed by living organisms, a process called methylation.

Until the 1970s, researchers say, atmospheric mercury generally rose because of industrial activity in Europe and North America. Levels declined after those sources started following emission controls, but then rose again after Asia became an industrial force.

While Researchers note in their study that "there are no ancillary environmental data from the time period of the study in Russia," the differences across the Arctic "may be explained by differences in water quality, geological bedrock formations, and proximity to polluting sources."

Metallurgic industries in Russia's Murmansk region and smelter operations in the Pasvik watershed led to atmospheric mercury levels in the Pasvik River, so the economic slowdown in those areas lowered the resulting pollution, the research showed.

Concentrations of mercury in fish found within the Mezen River were lower than 10 other locations, but higher than eight in North America. Mercury levels in burbot, a cod-like fish in the Lena River, were among the lowest, the study said.

"Good news since the Lena River is one of the largest watersheds in the world," said Castello.

Mercury concentrations from fish in the Mezen and Lena rivers also were found to have been on a decline by 2.3 percent a year, though they have been increasing in North America by 5 percent a year.

"More studies are needed in the Russian Arctic if we are to better understand how mercury moves through this type of environment," Castello said.

In burbot in the Canadian Arctic, mercury concentrations in fish tissue have increased, despite declining atmospheric concentrations, because rising temperatures appear to increase availability of mercury to fish populations.

Better understanding the effect of industry on Arctic mercury levels has been confounded by climate change, Robert Spencer, an associate scientist at the Woods Hole Research Center, said in a statement.