Mercury levels going down in Minnesota lakes

The fish are safe to eat again in twelve Minnesota lakes, thanks in part to a statewide shift away from coal-burning power toward wind and solar energy.

The Allen S. King Generating Station, located on the St. Croix River in Oak Park Heights, will be decommissioned in 2028. It is one of only two coal-burning power plants in Minnesota that are still in operation. The Sherco Station in Becker will close in 2030. Both plants are operated by Xcel Energy.

For decades, atmospheric mercury has been a leading cause of water pollution in Minnesota lakes. The mercury is released during industrial processes such as artisanal gold mining and burning coal for electricity. Once in the atmosphere, it travels hundreds – even thousands of miles, and then “falls out” into our lakes and forests. Mercury bio-accumulates in the bodies of fish and other wildlife and can cause neurodegeneration and organ damage in people who eat too many mercury-laden fish. Currently, there are fish consumption advisories in 1608 Minnesota lakes due to mercury.

Statewide safe eating guidelines apply to fish from any lake or river. Some lakes in Minnesota have additional fish consumption advisories due to mercury and other toxins.

Happily, routine biomonitoring shows that mercury levels are actually falling in many Minnesota lakes. In 2020, the MPCA removed Forest Lake, Tanners Lake (Oakdale), Owasso (Roseville/Shoreview), Johanna (Arden Hills) and eight lakes in northern Minnesota from the state’s impaired waters list. This was the first time in Minnesota history that any lake or river recovered from a mercury impairment. In addition, scientists have observed declining mercury levels in the Great Lakes and in sediment cores from other lakes around the state.

What is the reason for this recent improvement?

There has been a 70% reduction in mercury emissions statewide since Minnesota developed its mercury-reduction plan in 2007. This is mostly thanks to coal burning power plants that have been retired or converted to burn natural gas. Additionally, mercury bans in many products mean that there are fewer emissions from garbage incinerators as well.

Xcel is currently building up its wind and solar infrastructure in order to be carbon-free by 2050.

Mercury emissions in Minnesota and other parts of the United States are expected to continue declining in the coming decades. Xcel Energy will decommission its coal-burning plant in Oak Park Heights in 2028 (the plant is currently only used six months per year) and will close the Sherco Station in Becker in 2030. The company is also closing coal-burning plants in Colorado. The plan is to build up wind and solar infrastructure in order to be carbon-free by 2050. Xcel also produces 30% of its electricity at nuclear power plants in Monticello and Prairie Island. 

Previously, MPCA scientists had not expected local mercury reductions to have much of an impact on Minnesota lakes because global emissions are still rising. However, it turns out that some of the mercury in lakes comes to the water indirectly from leaves in the surrounding watershed that also capture mercury from the air. As a result, cutting mercury emissions in Minnesota and other parts of the United States creates an outsized benefit for water and wildlife.  

Forest Lake is one of 12 Minnesota lakes that has “recovered” from mercury contamination and no longer has a fish consumption advisory.

Want to help protect Minnesota’s lakes and rivers from mercury contamination? Here are a few resources to get started:

  • Schedule a home energy audit. The Home Energy Squad offers audits for Xcel and CenterPoint Energy customers for $70 or $100 (free visits available for low-income households). Energy advisors identify ways to lower heating, cooling, and electricity costs and install LED lightbulbs, door and attic hatch weather-stripping, programmable or smart thermostats, and high-efficiency water fixtures.
  • Dispose of household hazardous waste at the Washington County Environmental Center (4039 Cottage Grove Drive, Woodbury). The center removes the mercury in thermostats, thermometers, fluorescent lights, gauges, medical and scientific equipment, electrical devices, and household appliances so that these products can be disposed of safely.
  • Learn more about solar, wind and other forms of clean