Study finds antibiotics in Minnesota groundwater

Published 5:08 pm Saturday, June 28, 2014

ST. PAUL — A government study finds that measurable levels of antibiotics, detergents and other consumer chemicals are turning up in Minnesota’s groundwater.

The chemicals apparently come from landfills, septic systems and sewage treatment systems. They’ve been found in surface waters in recent years. But the new survey is the most extensive evidence yet that the chemicals are also making their way into both shallow and deep aquifers in the state.

Groundwater supplies drinking water for three-fourths of Minnesota residents. The study, conducted between late 2009 and mid-2012 by the U.S. Geological Survey and the Minnesota Pollution Control Agency, found no chemicals in excess of drinking water quality standards.

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But neither the state nor the federal government has set health-based water quality standards for four of the most common chemicals it found — the antibiotic azithromycin, the antihistamine diphenhydramine, the flame-retardant tributyl phosphate and the animal antibiotic lincomycin.

The chemicals come from a variety of consumer and industrial products, including prescription and over-the-counter drugs, lotions and detergents.

“Our use of these chemicals in our everyday lives is releasing them at low levels into our environment,” USGS groundwater specialist Mindy Erickson said. “Our question as a society is, ‘What do we think about that?’”

The 118 wells tested for the study were chosen because of their assumed vulnerability to this kind of contamination, said Sharon Kroening, research scientist at the MPCA. Some were in the Twin Cities area, some near St. Cloud and others in north-central, northwestern and southeastern Minnesota.

The report suggests the chemicals find their way into groundwater from a variety of sources.

For example, the chemical found most often was a common antibiotic, sulfamethoxazole. It was found in more than 10 percent of the samples, mostly where septic systems are prevalent, though in concentrations well below levels considered dangerous. Bisphenol A, used in making hard plastic bottles and other products, was present mostly in wells near closed landfills.

The Minnesota Department of Health has been studying contaminants of emerging concern for several years. The new groundwater information could generate a closer look, particularly at the four commonly found contaminants, said Helen Goeden, a toxicologist for the department.

Goeden said she didn’t consider the report cause for alarm, but it should make people more aware.

“People are complacent about their drinking water. Reports like this help inform,” she said.