Synthetic female hormones in sewage are toxic to male fish over generations

By Kristen Keteles

I’m a toxicologist at EPA in Denver, Colorado, and I study how pollutants can affect ecological and human health. I work with a team of scientists from academia (Colorado State University, University of Colorado Denver) and U.S. Geological Society to understand the potential effects of hormones and medications that are discharged into the environment. Did you know a very potent synthetic female hormone used in prescription drugs can be found in water and could be harming fish? We’re finding in our study that it can wipe out fish populations over several generations, and it’s the male fish that are most affected. Some studies have found that male fish below waste water treatment plants, and exposed to female hormones, can lose their masculine characteristics and become indistinguishable from females. Our new study found that a potent form of the female hormone estrogen used in prescription drugs not only causes the males to look female, it also appears to be toxic to male fish and these effects may impact future generations of fish.

Where do these hormones and medications come from? All of us. Humans excrete hormones and medications, which often end up in our rivers and streams from sewage. Disposing of medications by flushing can also contribute to pharmaceuticals in the environment. A growing human population, combined with effects of climate change like decreasing precipitation, has resulted in many streams containing higher concentrations of waste water. In fact, some streams in the west are 90% waste water. Not a nice thought if you like to kayak and fish, like I do. The water IS treated, but many hormones and pharmaceuticals are not completely removed by the waste water treatment plants. So, more people and less water equals more hormones and drugs in the water. My team is trying to determine what this means for fish, and ultimately for people, too. Although, currently, EPA does not have water quality standards for these types of chemicals, our study may help determine if such water quality standards are needed.

We looked at effects of exposure to a synthetic estrogen used in prescription drugs to fathead minnows over multiple generations by conducting experiments, both in the laboratory and in outdoor water tanks that mimic natural conditions.

Chemical exposure to female hormones in prescription drugs was found to increase the chances of death in male fish, but not females. And, fish exposed when they were young, but not as adults, were not able to reproduce later on in life. In addition, fish that weren’t even exposed to the prescription drugs, but were born to parents who were exposed, were less likely to reproduce. It could be that synthetic estrogen in prescription drugs, combined with other natural and synthetic hormones in the water, are reducing male fish fertility and could affect fish populations.

This is why it’s important to do what we can to protect fish breeding habitats in unpolluted areas. What are some things that your community can do to protect fish habitat? Read our information on how to dispose of unused medications to reduce the amount of pharmaceuticals that end up in water.

About the author: Kristen Keteles is a toxicologist in the Support Program of the Office of Ecosystems Protection and Remediation in EPA Region 8 in Denver. She has been with EPA for six years.

Fish A is a normal male fathead minnow. Fish C is a normal female fathead minnow. Fish B is a male that was exposed to female hormones in prescription drugs and looks more like a female than a male.

Fish A is a normal male fathead minnow. Fish C is a normal female fathead minnow. Fish B is a male that was exposed to female hormones in prescription drugs and looks more like a female than a male.

 

EPA Fish Team scientists: Al Garcia, Kristen Keteles, Elaine Lai, and Adrian Krawczeniuk.

EPA Fish Team scientists: Al Garcia, Kristen Keteles, Elaine Lai, and Adrian Krawczeniuk.