After an exhaustive seven-year research effort, Canadian biologists found that miniscule amounts of estrogen present in municipal wastewater discharges can decimate wild fish populations living downstream.

Male fish exposed to estrogen become feminized, producing egg protein normally synthesized by females. In female fish, estrogen often retards normal sexual maturation, including egg production.

The research, led by Dr. Karen Kidd, an NSERC-funded biology professor at the University of New Brunswick (Saint John) and the Canadian Rivers Institute, confirms that synthetic estrogen used in birth control pills can wreak havoc on the sex lives of fish.

“We’ve known for some time that estrogen can adversely affect the reproductive health of fish, but ours was the first study to show the long-term impact on the sustainability of wild fish populations,” explains Kidd. “What we demonstrated is that estrogen can wipe out entire populations of small fish ? a key food source for larger fish whose survival could in turn be threatened over the longer term.”

Kidd says the risk is greatest for aquatic ecosystems downstream from municipalities that either discharge untreated wastewater or maintain only primary treatment facilities.

Of less concern near cities that remove a wide range of chemical contaminants, including estrogens, from wastewater using secondary and tertiary treatment processes.

In fact, according to researchers, the research also found that removing estrogen through wastewater treatment can reverse the adverse impact of the hormone on wild fish.

To better understand the impacts of estrogen on fish, the researchers conducted a seven-year, whole-lake study at the Experimental Lakes Area in northwestern Ontario. Over three summers, they added tiny amounts ? low parts per trillion ? of the synthetic estrogen used in birth control pills to the lake to recreate concentrations measured in municipal wastewater.
During that period, they observed that chronic exposure to estrogen led to the near extinction of the lake’s fathead minnow population as well significant declines in larger fish, such as pearl dace and lake trout.

“Generally, the smaller the fish, the more vulnerable they are to estrogen,” said Kidd.

Kidd and her colleagues reported the findings last year in the Proceedings of the National Academy of Sciences of the United States of America. The research is to be presenting at the 2008 American Association for the Advancement of Science (AAAS) Conference.

Source
Eureka Alert