Water contaminated with residue from birth-control pills can bend the gender of male fish, according to Canadian researchers who presented scientific findings last week to the American Chemistry Council. In the most controlled experiment to date to examine the effects of estrogen on ecosystems, Canadian scientists deposited birth-control pills in a remote lake in Ontario for three years. As a result, all male fish of all species in the lake were “feminized” — some grew eggs in their testes, others simply couldn’t reproduce. The experiment was designed to mimic the impact that the female hormone estrogen may be having in bodies of water in North America as sewage systems flush out wastewater that contains estrogen from birth-control pills and hormone-replacement therapy. A number of U.S. government scientists are concerned that female hormones could be harming wildlife, and some are investigating whether estrogen and other chemicals that act like estrogen could be affecting human males as well.