"Researchers have found that pharmaceuticals and personal-care byproducts persist at low levels miles from sewage discharge pipes in Lake Michigan. And a study from the University of Wisconsin-Milwaukee shows that the most prevalent drug in the lake — the Type 2 diabetes medication Metformin — changes the hormonal system of fish exposed to it.

But what long-term effects it may have on fish and their ability to reproduce are unknown.

In the research group's latest study, fathead minnows were exposed to Metformin at the levels found in Lake Michigan for four weeks. Male minnows showed disruption of their endocrine systems, producing a chemical messenger usually associated with females' egg production, said Rebecca Klaper, a professor and research scientist at the university's School of Freshwater Sciences."

Keith Matheny reports for the Detroit Free Press January 15, 2015. [2]