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St. Paul, Minn.— A new study released by the Minnesota Pollution Control Agency confirms that lakes and streams across Minnesota are contaminated by a variety of pharmaceuticals, ingredients from personal care products, and endocrine-disrupting compounds.  This is the latest in a series of studies investigating the presence of these chemicals in Minnesota’s surface water.

Even in remote areas of the state, chemicals such as antibiotics, nicotine breakdown products, antidepressants, and medications to regulate diabetes, cholesterol, and blood pressure, were detected. The insect repellent DEET was detected in 91% of the lakes studied. These results are consistent with previous studies of Minnesota lakes and rivers.

“We have known for some time that these compounds frequently turn up downstream from wastewater treatment plants,” said the study’s lead author, Mark Ferrey. “And 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.”

Ferrey noted that septic systems and stormwater runoff are among the potential sources of contamination to surface water not impacted by wastewater treatment plants.  While it is not yet clear how these compounds are entering more remote lakes and streams, Ferrey noted that it is possible that these contaminants are sometimes being distributed by rainfall or atmospheric transport of dust to which these chemicals are attached.

The study tested 11 lakes and 4 streams that were previously sampled for the presence of 125 different compounds-- mostly pharmaceutical products, but also some ingredients that are used in cosmetics, detergents, and hygiene products. Some of the compounds were included in a 2008 round of testing, but the most recent report tested for many new chemicals. This study was the first in Minnesota to look for the x-ray contrast drug iopamidol, which was found in 73% of the lakes studied. Interestingly, the highest concentration of iopamidol was found in Lake Kabetogama, located in the Voyageurs National Park.

“We know more now than we have in the past about what contaminants consistently show up in surface water,” said Ferrey. “And we’re also beginning to better understand how these contaminants can affect fish and other organisms in the environment.”

Research into how these compounds might affect human health through long-term, low-level exposure is still in its early stages. The MPCA works with the Minnesota Department of Health in evaluating potential human health impacts of these chemicals. Ferrey noted that it is especially difficult to predict environmental and health effects of exposure to multiple pharmaceuticals in combination.

Because some pharmaceutical contamination of surface water is due to wastewater, the MPCA advises that people avoid flushing unwanted medicines down the toilet.

The full report is available on the MPCA’s website.