Saturday, March 24, 2007

Effects of a Synthetic Estrogen on Aquatic Populations

Interesting study:

Effects of a Synthetic Estrogen on Aquatic Populations: a Whole Ecosystem Study, conducted by the Freshwater Institute of Fisheries and Oceans Canada.

The study concerned the effects on aquatic life exposed to ethynylestradiol, a synthetic estrogen used in hormone replacement therapy and birth control pills that is excreted by women; ethynylestradiol is not completely broken down during sewage treatment, and so it ends up in waterways. It looks like the results of this 2-year study were published in 2004, and the Freshwater Institute in Canada is continuing to study the issue in order to assess long term effects. I am not aware, however, if any other more recent studies have been done on this particular issue. If my readers are aware of anything more recent, feel free to comment.

This is from their executive summary:
Municipal wastewater treatment plants (MWTP) discharge numerous contaminants into aquatic systems, and some of these chemicals are known or believed to act like hormones and interfere with the growth, reproduction and development of aquatic organisms. It is becoming increasingly apparent that male fish exposed to these effluents are becoming feminized due to the presence of natural and synthetic estrogens in the water. The potent synthetic estrogens excreted by women taking hormone replacement therapy or birth control pills are not completely broken down in the sewage treatment process and are discharged into waterways. The male fish exposed to these estrogens produce egg proteins, have smaller gonads and, in the more severe cases, develop eggs...

During the summer of 2001, the synthetic estrogen used in birth control pills, ethynylestradiol, was added continuously to one lake to maintain low and environmentally-relevant concentrations in the water. Laboratory and field studies had previously demonstrated that this estrogen does not persist in the water, and can be degraded by bacteria naturally present in the sediments of the lake. The additions were done from the end of May until the end of October, and mean concentrations of the estrogen were 6.1 ng/L in the surface waters of the lake. We monitored the lake for responses of the individual fish (lake trout, sucker and minnows) and their populations, as well as changes in the tadpoles, bacteria, algae, leeches, zooplankton and benthic invertebrates as a result of the estrogen additions.

This study was successful at reproducing some of the impacts seen in fish downstream of MWTPs. Male fish from the estrogen-addition lake produced high concentrations of egg protein precursors, had developmental delays in their gonads and, in one species of minnow, produced eggs. Female fish exposed to the estrogen also showed delays in reproductive development and changes in the amount and timing of the egg protein production. The kidneys and livers were also impacted likely due to the atypical and high production of egg proteins in these fish. In the fall of 2001, we did not see any changes in the sizes of the fish populations, fish growth rates, the numbers of males versus females, and the survival of the offspring. It is likely that population- level responses of long-lived organisms will take longer to appear, and for this reason we are continuing to monitor the fish populations in this lake for 3 years following the estrogen additions.

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