Chemicals in water supplies produce feminizing effects, lower sperm quality.

• Author: Powers, Shawn
• Position: Environmental Intelligence

Adding to a growing body of research on the impacts of endocrine disrupting compounds in freshwater, two recent studies have confirmed previously suspected effects of estrogen-mimicking chemicals on humans and wildlife. One study, led by Karen Kidd of the Canadian Freshwater Institute, found that a synthetic estrogen used in contraceptives and hormone therapy pills can feminize male fish of several freshwater species. Kidd's team introduced ethynylestriadol (EE2) into a remote Ontario lake, maintaining a concentration (about 5 nanograms per liter) well within the range of EE2 concentrations observed in polluted surface waters. The synthetic hormones, which resist breakdown by stomach acids and are seldom removed by treatment plants, contaminate water through human excreta and improper disposal of pills.

All of the male fish in the lake began producing vitellogenin, a precursor to egg proteins, and one-third of the Pearl Dace minnows grew eggs in their testes. Some fish stopped producing sperm, and one species lost all external signs of maleness. Small minnows were the most severely affected; the fathead minnow's reproduction apparently ceased altogether. "We didn't see any young [fathead minnows] last year and don't expect to see any this year," said Kidd.

According to Kidd, introducing estrogen into previously untainted water was necessary to establish a link between EE2 and feminization. While contamination by synthetic estrogen and feminization of male fish are both well-documented phenomena, inferences about cause and effect have been complicated by the suite of other chemicals commonly found in polluted surface waters. Previous studies also did not consider whether the feminized species could still reproduce.

Another study, led by Shanna Swan of the...