So many humans are taking Prozac that traces of the antidepressant drug are showing up in the Great Lakes of the United States, where bacteria are dying as a result. Microbiologist Steve Mauro has studied water samples from the Great Lakes in Erie, Pennsylvania, and found that Prozac ingredient fluoxetine is killing E. coli, a common bacteria that lives in many places, including the human gut.

Writes Rachel Kaufman in National Geographic:

What's puzzling is where the drug is coming from. Fluoxetine is thought to enter waterways after it passes through the body and is excreted in urine. And pill users who dispose of unused pills down the sink could be adding to the problem. Wastewater treatment plants generally don't filter out the chemical.

But near Presque Isle State Park in Lake Erie, where the water samples containing fluoxetine were found, "there's no particular fallout. We don't have a direct sewage outfall located anywhere near the beaches," Mauro said. That means the fluoxetine is likely spread out all over the lake, he added.

Previous studies have suggested that fluoxetine might harm small marine creatures like mollusks, as well as damaging the brains of fish. Ultimately Mauro's discovery is further proof that the drugs humans take can affect the environment in unexpected, indirect ways. Our bodies are part of the ecosystem in a fundamental way.

via National Geographic (Thanks, Marilyn Terrell!)