"Closer to home, we have observed intersex White Perch in various locations in the Great Lakes, " explained Chris Metcalfe, professor of Environmental and Resource Studies at Trent University in Ontario. "And in the Columbia River, there is a much higher proportion of female salmon than males, indicating that some feminization process may be going on."

Metcalfe conducted lab experiments on aquarium fish to try to find out which of the various forms of estrogen were the culprit in the sexual alteration of fish. He will report his research findings as well as share new statistics on estrogen concentrations in water that were generated by the Canadian Department of Environment in Burlington, Ontario, on Monday, November 5, at the Geological Society of America's annual meeting in Boston.

Metcalfe found that very low levels of the estrogen hormones, 17 alpha-ethinylestradiol, 17 beta-estradiol, estrone and estriol, caused intersex and altered sex ratios in the aquarium fish.

"Ethinylestradiol is the active ingredient in the birth control pill," he said. "The other compounds are the natural female estrogen (beta estradiol) and metabolites of that compound excreted by women."

Metcalfe also found from his experiments that estrogen-mimicing degradation products of alkylphenol ethoxylate surfactants (compounds used in such things as pesticides, detergents, and cosmetics) and the plasticizer, Bisphenol A (used in lacquers for dental treatment and to coat food cans and other metal containers), had little or no estrogenic effects on the fish. He believes that it is the female estrogen hormones released from sewage treatment plants that are responsible for the feminization of wild fish.

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Contact: Ann Cairns
617-954-3214
Geological Society of America
5-Nov-2001