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Mercury levels rise in Minnesota fish

Mercury concentrations in northern pike and walleye have increased since the mid-1990s, after a substantial decrease over the previous decade, according to a study released Tuesday, the Pioneer Press reported.

The Minnesota Pollution Control Agency conducted the study, which was published last week in Environmental Science & Technology. The data were collected from fish in 845 Minnesota lakes, the Star Tribune reported.

The results are surprising, MPCA scientist Bruce Monson told the Pioneer Press. The increase in methylmercury is a concern, because it contaminates fish, and can harm humans or other plants and animals.

Monson and the other MPCA scientists have concluded that the primary source of the mercury is unlikely to be local, since the observed increase is statewide, the Star Tribune reported.

Increased mercury emissions worldwide, as well as global climate change, contribute to the problem. Emissions in Minnesota, however, have decreased significantly over the past two decades, the Pioneer Press reported.

The mercury in the atmosphere can be converted into methylmercury by aqueous bacteria, and enters the food chain, resulting in high concentrations among large predatory fish, the Star Tribune reported.

The MPCA scientists are advocating for addressing the issue by reducing mercury emissions internationally, the Star Tribune reported.