Water pollution is not exactly an underappreciated concern. For years state and federal officials have been working with experts to improve water quality, limit pollution, and test for potential consequences. However, it should go without saying that things can be overlooked. That appears to be the case concerning pollution from a common diabetic drug, which may now be poisoning fish in Lake Michigan.

That's at least according to a team of researchers with the School of Freshwater Sciences at the University of Wisconsin-Milwaukee (UWM), who recently tested supposedly treated water from the South Shore sewage facility in Oak Creek, Wisconsin.

The team told the local Journal Sentinel that they found a disturbingly high concentration of metformin, a first-line treatment for type 2 diabetes that remains the most commonly prescribed of its kind of drugs on the market.

Rebecca Klaper, a freshwater science expert from UWN, added that concentration levels were so high that it was easily detected even two miles off the shore of Lake Michigan.

"It was kind of a surprise," she told the Sentinel. "It was not even on our radar screen. I said, 'What is this drug?'"

She didn't wait long to find out. As described in a study recently published in the journal Environmental Toxicology and Chemistry, Klaper and her colleagues determined that at the stunning concentrations seen in the lake (up to 40 parts per billion), the metformin could adversely affect adult fish populations.

The researchers noted early on that the amount of metformin these fish were being exposed to is still far lower than what an actual diabetic would need. After all, the drug was reaching waters only because it is not broken down completely after it's taken and then excreted by a human.

However, these fish are swimming in the drug in a very literal sense, exposed to it 24/7. To measure the potential consequences of this, Klaper and her team exposed adult fanhead minnows to various metformin concentrations in a lab for four weeks. The minnows represented wild populations seen in Lake Michigan, and the drug exposures also mirrored tested lake conditions.

They quickly found strong evidence that the drug's presence was disrupting endocrine processes in male fish - which can lead to problems with growth and reproduction. Most notably, the males were producing biochemicals that are normally only seen in females and are associated with the production of eggs.

Klaper and her colleagues argue that while more investigation is needed, these results alone are more than enough to prove that overlooked chemicals cannot simply be ignored under the assumption that they will dilute to "harmless" levels in large bodies of water like Lake Michigan.

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