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New study finds estrogen has detrimental and surprising effects on freshwater wildlife

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WINNIPEG—October 14 2014—The International Institute for Sustainable Development-Experimental Lakes Area (IISD-ELA) and the University of New Brunswick today release the findings of a study that show that the birth control pill has unexpected effects on aquatic ecosystems.

The study, published in the most recent issue of a prestigious British science journal, found that introducing synthetic estrogen, found in the birth control pill, into a lake negatively affected the reproductive cycles of fathead minnow and led to a near extinction of the population. The estrogen interfered with the minnow’s ability to reproduce.

Once minnow numbers dropped, other aquatic species responded to the loss in food supply or predation. This cascading response in the lake was unexpected and suggests the risks of estrogens in the surface waters may be underestimated.

Estrogens can enter our rivers and lakes via municipal effluents and can originate from various sources, such as urine from females and feedlots. They cause male fish to develop eggs, in the more severe cases, and feminized male fish have been found in rivers across North America.

 ”We were surprised when the population of fathead minnow collapsed shortly after the whole lake study started. The minnows were very sensitive to low concentrations of this synthetic estrogen” says Karen Kidd, University of New Brunswick Saint John and the study’s lead author.

“The big drop in minnow numbers affected other aquatic life in the lake because the main food supply had disappeared for the bigger fish, and aquatic insects were no longer being eaten by the minnows. This was another surprise and suggests greater impacts of estrogen discharges to surface waters than we previously thought.”

The study is one of the examples of whole-ecosystem experimentation that is possible at IISD-ELA, a research facility in Northwestern Ontario, Canada that comprises 58 small lakes and their watersheds.

 “Thanks to the benefits of whole lake experimentation, we were able to manipulate these small lakes and examine how all aspects of the ecosystem—from nutrients to fish populations—respond. Small-scale studies would never have revealed the true environmental impacts, such as impacts on population sizes, of estrogen in municipal waterways,” says Michael Paterson, chief research scientist at IISD-ELA and a co-author on the study.

The study “Direct and indirect responses of a freshwater foodweb to a potent synthetic oestrogen,” was released on October 13 2014. Philosophical Transactions of the Royal Society B is the world’s first science journal. The issue - Assessing risks and impacts of pharmaceuticals in the environment on wildlife and ecosystems - focuses on the current understanding of pharmaceuticals in the environment.

For more information please contact Sumeep Bath, IISD media and communications officer, at or +1 (204) 958 7740.

UNB Media Contact: Karen Kidd, Professor and Canada Research Chair, Biology Department, University of New Brunswick Saint John,

Aerial photo of experimental Lake 260 (photo credit K. Kidd)

Water sampling on experimental Lake 260 (photo credit K. Kidd)

Fathead minnow in experimental Lake 260 (photo credit J. Shearer)

About the International Institute for Sustainable Development

The International Institute for Sustainable Development (IISD) is an independent think tank that delivers the knowledge to act. Our mission is to promote human development and environmental sustainability. Our big-picture view allows us to address the root causes of some of the greatest challenges facing our planet today – ecological destruction, social exclusion, unfair laws and economic and social rules, a changing climate. With offices in Winnipeg, Geneva, Ottawa and Toronto, our work impacts lives in nearly 100 countries.

For more information, please contact: or +1 (613) 238 2296 ext. 114