Male fish producing eggs; is pollution to blame?

WASHINGTON — Abnormally developed fish, possessing both male and female characteristics, have been discovered in the Potomac River in Washington, D.C., and in tributaries across the region, federal scientists say — raising alarms that the river is tainted by pollution that drives hormone systems haywire.

The fish, smallmouth and largemouth bass, are naturally males but for some reason are developing immature eggs inside their sex organs. Their discovery at such widespread sites seems to show that the Potomac's problem with "intersex" fish extends far beyond the West Virginia stream where they were first discovered in 2003.

The cause of the abnormalities is unknown, but scientists suspect a class of waterborne contaminants that can confuse animals' growth and reproductive systems. These pollutants are poorly understood, however, leaving many observers with questions about what the problems in fish mean for the Potomac and the millions of people who take their tap water from it.

"I don't know, and I don't think anybody knows, the answer to that question right now: Is the effect in the fish transferable to humans?" said Thomas Jacobus, general manager of the Washington Aqueduct, which processes Potomac water to provide drinking water for residents of Washington, Arlington County, Va., and Falls Church, Va.

Jacobus, like other officials at area utilities, said there was no evidence that tap water taken from the Potomac was unsafe to drink. They said humans should be far less susceptible to the river's pollution than fish are, because people are not exposed constantly to the water, their hormone systems work differently, and their larger bodies should require higher doses of any pollutant to cause problems.

Pollutants that mimic hormones have emerged as a worldwide concern in the past decade. Scientists say the research is in its infancy, but they have identified pollutants that might affect animals, including human estrogen from processed sewage, animal estrogen from farm manure, some pesticides and soap additives.