According to a news release from Virginia Tech, mercury concentrations in fish are much lower than anticipated.

For years, researchers have assumed that if mercury is high and increasing in fish in the North American and European Arctic, the same must be true of fish elsewhere in the Arctic. However, an international team of researchers has found that assumption is incorrect in much of the continental Arctic.

“It turns out 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,” posited Leandro Castello, an assistant professor of fish and wildlife conservation at Virginia Tech, in a statement.

Atmospheric mercury originates primarily from mining and ore processing, according to a United Nation’s environmental program study. Under certain water conditions, mercury is transformed into a special form that can be absorbed by living organisms, through a process known as methylation.

“Methylmercury is highly toxic,” noted Castello.

However, the researchers discovered that burbot fish in two Russian rivers, the Lena and the Mezen, are safe to consume. The fish from these rivers were examined in contrast to burbot from 20 spots along the Pasvik River on the Norwegian-Russian border and along the Mackenzie River in Canada, where years of research have discovered high levels of mercury that make the fish unfit for consumption.

“The burbot fish was chosen because they are top predators that integrate many bio-geo-chemical processes in the river watersheds,” explained Castello. “The fish were collected downstream of the watersheds, so that they would present everything that happened upstream.”

Mercury concentrations from fish in the Mezen River were lower than 10 spots, but higher than eight in North America, while mercury levels in burbot in the Lena River were among the lowest.

Mercury concentrations from fish in the Mezen and Lena rivers also were discovered to have been on a declibe by 2.3 percent a year, whereas in North America they have been rising by five percent a year.

The variations across the Arctic “may be explained by differences in water quality, geological bedrock formations, and proximity to polluting sources,” wrote the researchers in their paper.

Rising atmospheric mercury concentrations began to decline in the 1970s in Europe and in North America due to emission controls, while the economic decline near the watersheds of the Lena and Mezen decreased polluting activity there.

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

The study’s findings are described in greater detail in the journal Environmental Science & Technology.