A new study shows the surprising damage that birth control pills can do to freshwater ecosystems.

The study was conducted at the Experimental Lakes Area near Kenora, with the findings published in the most recent issue of a prestigious British science journal.

Michael Rennie is a research scientist and served as one of the lead authors on the study. He said there has been evidence for years that different types of fish downstream from municipal wastewater outlets can develop sex development disorders. "The question is could we figure out why these fish were essentially changing their sex," Rennie explained in an interview with the CBC.

Researchers at Experimental Lakes Area near Kenora

Researchers at the Experimental Lakes Area near Kenora. Synthetic estrogen added to the water had a dramatic impact on the ecosystem (K Kidd)

To find out, researchers added small amounts of synthetic estrogen to a lake to reflect what comes downstream from a wastewater plant. Two interesting components emerged, according to Rennie.

Scientists found that among the fathead minnow population, males started to produce eggs and their behaviour changed. The fish couldn't reproduce for almost five years after the addition of the estrogen to the lake.

Rennie said he was surprised by the extent of the impact. "I don't think anyone predicted there would be a total recruitment failure for the fathead minnows, that they would stop reproducing entirely. That's a pretty dramatic effect."

The bigger issue for Rennie was the impact on the whole ecosystem. "The loss of the minnows caused a ripple effect including a decline in the lake trout population."

As for what can be done about the impact of estrogen in water systems, Rennie said technologies are being developed to remove the components at treatment plants. However, there is a much larger question, he added. "It's about how to deal with the hormones, yes, but also about all pharmaceuticals at the waste treatment stage."