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

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 University of Missouri, demonstrated impacts of common pesticides with estrogen-like effects on sperm quality in human males. Swan's team tested over 400 Midwestern men--only two of whom were at occupational risk for pesticide exposure--for pesticide metabolites in their urine and for sperm quality using three measures.

The study revealed strong correlations between exposure to three common pesticides and poor sperm quality. The men most heavily exposed to atrazine, diazinon, and alachlor were 11, 17, and 30 times, respectively, more likely to have low sperm quality. Swan could not say with certainty how the men became exposed to the pesticides, but strongly suspects drinking water, as the chemicals are known to contaminate water supplies and are not removed by most of the water treatment processes currently used.

These ongoing studies raise troubling questions about other low-level water contaminants, especially pharmaceuticals and personal care products. Many public water supplies are cocktails of small amounts of antibiotics, hormones, veterinary medicines from livestock and pets, antacids, cholesterol-lowering drugs, codeine, anti-depressants, sunscreens, chemotherapy agents, pain relievers, caffeine, and potentially hundreds of other chemicals and metabolites. While these contaminants are attracting increasing attention among researchers at the U.S. EPA and other institutions, their impact on human and ecological health remains poorly understood, and regulatory intervention may still be years away.