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Minnesota Lakes, Rivers Show Evidence Of Chemical Contamination

More than 90 percent of lake samples also showed evidence of DEET.

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Minnesota environmental officials found widespread evidence of chemicals from pharmaceuticals, personal care products and other materials in a recent study of state waterways.

Researchers from the Minnesota Pollution Control Agency tested 11 lakes and four streams for the presence of 125 compounds in 2013.

The analysis found 56 chemicals in rivers downstream from wastewater treatment plants, with 33 chemicals in upstream waters. The lakes, meanwhile, showed evidence of 27 chemicals.

The study found chemicals in both highly populated and remote areas. Traces of the x-ray drug iopamidol showed up in about three-quarters of the lake samples, but the highest concentration was in pristine Voyageurs National Park.

More than 90 percent of lake samples also showed evidence of the common insect repellant chemical DEET.

Analysts offered several potential causes for the presence of dozens of chemicals upstream from water treatment plants, including septic systems, stormwater runoff or transmission via rainfall or dust.

β€œWe have known for some time that these compounds frequently turn up downstream from wastewater treatment plants,” said lead author Mark Ferrey. β€œAnd recent research has shown that a surprising number are found even in remote lakes or upstream waters. But we have a lot to learn about how they end up there.”

The results were consistent with a 2008 study of the same waterways. A study released in 2013 showed evidence of chemical contamination in 50 Minnesota lakes.

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