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Study: Minn. groundwater contamination levels low

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Map: MN groundwater contaminants
Wells with detections of endocrine active compounds and other contaminants of emerging concern in Minnesota's groundwater, 2009-2010.
Courtesy of Minnesota Pollution Control Agency

A new study finds Minnesota groundwater is contaminated with low levels of chemicals, but the chemicals are not as widespread in groundwater as they are in lakes and streams.

This is the first study to examine groundwater across the state for "chemicals of emerging concern." Researchers tested 40 shallow wells around the state for 92 contaminants. They found 20 different contaminants. One or more chemicals were found in about one-third of the sampled wells.

Minnesota Pollution Control Agency scientist Sharon Kroening said the chemicals come from products like plastics, medications, detergents, insect repellents and fire retardants.

"The ones that we found most commonly in this round of sampling was a fire retardant, tris dichloroisopropyl phosphate, an antibiotic, sulfamethoxazole, and two plasticizers, one that's pretty well known called bisphenol A, and another one called tributyl phosphate," Kroening said.

The most chemicals were found at wells near landfills. Researchers also found a higher incidence of chemicals in wells near residential areas with septic systems.

The chemicals were all found at very low levels.

Steve Thompson, supervisor of the MPCA groundwater and stream monitoring unit, said very little is known about the health risk for most of these chemicals. But he said the low levels of chemicals should not be a major cause for concern.

"Probably 85 percent of them we do not have toxicological information on — which is why it's so important to find out what is there and which ones are most commonly present so we can start taking a look at those," Thompson said.

The state Health Department will set an exposure limit for the emerging chemicals.

Michele Ross heads the department's health risk assessment unit and said they want to establish health risk levels for the most common chemicals. While many have little risk at very low levels, others can be dangerous in extremely small amounts.

"But it's really the not knowing. That's a big part of what our program does," Ross said. "Just being able to answer that question for Minnesotans and relieve that anxiety and that uncertainty and provide some clarity on what ... they really mean."

The program developed standards for 10 chemicals in its first two years. The goal is to assess the health risk for six new chemicals each year.

The MPCA will continue to sample wells this year. They plan to expand the testing in residential areas with septic systems and near industrial sites.

The MPCA said this groundwater study cost about $400,000 and was paid for by the Minnesota Legacy Fund.