Traces of chemicals from common household products, legal prescription medications and illegal drugs are common in Minnesota lakes, according to a study released Monday.
Scientists from the Minnesota Pollution Control agency chose 50 lakes at random and tested them for 125 chemicals, including substances that mimic or interfere with the actions of naturally occurring hormones.
The common insect repellent DEET was found in 76 percent of lakes. BPA, a chemical used in plastics, showed up in more than 40 percent of the lakes sampled. The common antidepressant amitriptyline was in nearly 30 percent of the samples. And cocaine showed up in one-third of the lakes sampled.
This was the largest study of its kind among a series of studies done on the state's lakes.
"It's confirming what we found in our other studies, but it also showed us some new things that we didn't see before and that are new to us," MPCA researcher Mark Ferrey told Minnesota Public Radio (http://bit.ly/10lzDW6 ).
All of these chemicals are found at very low levels, often a few parts per trillion. To picture one part per trillion, think of a football field-sized swimming pool that's 43 feet deep and add one drop of water, the MPCA said.
Ferrey said even very low levels of drugs and other chemicals can affect fish and other life. He also said the sample of 50 lakes was large enough to reflect the condition of all Minnesota lakes.
"These studies, probably for the first time, are giving us the data that we can statistically extrapolate to say, `well, this is the condition of the lakes in our state,"' Ferrey said.
While the lake study identified an expanding list of chemicals, it didn't seek to answer the question of how the chemicals get into lakes. Sewage treatment plants and septic systems are often sources for pharmaceuticals and other chemicals.
But chemicals were found even in remote lakes with no roads nearby, and Ferrey said some things, such as cocaine, might settle into lakes from the air, while others might fall with the rain.
Ferrey pointed to recent research that found low levels of contamination cause behavioral changes in baby fish that make them less likely to survive, and studies in mice that found genetic damage for four generations after pregnant mice were exposed to BPA, the plastics chemical.
A related MPCA study released Monday focused on Minnesota's rivers and 18 chemicals, including several pharmaceuticals and personal care products. Parabens, a family of chemicals used as preservatives for food and cosmetics, were commonly found.
"What these studies really are measuring is the footprint of our society and how we live," MPCA Commissioner John Linc Stine said in a statement. "Our lakes and rivers are reflecting the chemicals we use and put into our bodies. These chemicals have very beneficial uses, but unfortunately they tend to stick around in the environment after their first use."
Information from: Minnesota Public Radio News, http://www.mpr.org
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