By David A. Fahrenthold
Washington Post Staff Writer
Wednesday, September 6, 2006
Abnormally developed fish, possessing both male and female characteristics, have been discovered in the Potomac River in the District 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 widely spread sites, including one just upstream from the Woodrow Wilson Bridge, seems to show that the Potomac's problem with "intersex" fish extends far beyond the West Virginia stream where they were first found 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 the District, Arlington County and Falls Church.
Jacobus, like others 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, because people are not exposed constantly to the water, our hormone systems work differently, and our larger bodies should require higher doses of any pollutant to cause problems. As research on the fish continues, other scientists across the region are trying to determine whether Potomac water or mud can affect human cells. This research, including tests at West Virginia University that examine whether cells react as if estrogen or estrogen mimics are present, has not reached any solid conclusions.
The first intersex fish in this area were found three years ago in the South Branch of the Potomac, a tributary more than 200 miles upstream from Washington. In 2004, more abnormal bass were discovered in a section of the upper Potomac near Sharpsburg, Md.
Following up, last fall federal and state researchers caught smallmouth bass in the Shenandoah River in Virginia and in the Monocacy River and Conococheague Creek in Maryland. All three tributaries eventually empty into the Potomac. At the site on the Potomac itself in the District, there are no smallmouth bass, so the researchers examined largemouth bass.
The results were striking, according to Vicki S. Blazer, a fish pathologist with the U.S. Geological Survey. More than 80 percent of all the male smallmouth bass they found were growing eggs, including all of the fish caught at four of the seven survey sites. The intersex condition doesn't change the fish's outward appearance but can be detected under a microscope.
At the site in Washington, seven of 13 male largemouth bass showed some kind of unusual feminine characteristic. Six of the seven fish tested positive for a protein used to produce eggs, and three of the seven contained eggs, Blazer said.
Taken together, Blazer said, the results on both bass species seemed to indicate that the Potomac watershed has a problem with "endocrine disruptors," contaminants that interfere with nature's chemical signaling. In this case, she said, the contaminants might have turned on bodily processes that normally are only active in female fish.
"What we're seeing now is that it's definitely not a problem just in the South Branch," she said. "There is this sort of widespread endocrine disruption in the Potomac, but we don't know still what are the causes."
Pollutants that mimic hormones have emerged as a worldwide concern in the past decade, blamed for problems in animals as diverse as alligators, minnows and polar bears. Although scientists say the research is in its infancy, they have identified a large array of pollutants that might affect animals, including human estrogen from processed sewage, animal estrogen from farm manure, some pesticides and additives to soap.
Blazer said water tests in the upper Potomac have detected low levels of a few known endocrine disruptors. But she said none of them has been pinpointed as a cause for the intersex condition, and the problem might be several pollutants acting in combination.
Also unclear is the effect on the Potomac's bass population. There have been several bad spawning years in the past decade, scientists said, and several large die-offs of smallmouth bass in the Shenandoah in recent years. But neither has been conclusively linked to the intersex problem.
Even less understood -- both in the Potomac and around the world -- is how these pollutants affect human health.
In 1996, Congress required the U.S. Environmental Protection Agency to help answer that question by developing a screening program to identify which chemicals are endocrine disruptors. Ten years later, the agency hasn't tested a single chemical, officials said.
Environmental groups have accused the EPA of proceeding too slowly. Agency officials have defended their efforts by saying the research has been more complex than expected.
"I would have hoped it would have been faster, but this is a very difficult program," said Clifford Gabriel, director of the EPA's Office of Science Coordination and Policy. "We want to make sure we get the science right."
In the area, at least four drinking-water utilities -- the Washington Aqueduct, Fairfax Water, the Frederick County authority and the Washington Suburban Sanitary Commission, which serves Montgomery and Prince George's counties -- take water from the Potomac. That has prompted some environmentalists to worry about problems in tap water, in light of the intersex problems in fish.
"If they can't tell us what the problem is," said Ed Merrifield, executive director of a group called Potomac Riverkeeper, "then how can they tell us that they've taken it out of the water?"
At the four utilities, officials said they felt confident that the Potomac water was being filtered and cleaned well enough that it posed no health risk from endocrine disruptors. But Charles M. Murray, general manager at Fairfax Water, said he wanted more certainty about those pollutants and their effects.
"The question is: Are we analyzing for the right things?" said Murray, whose utility serves a large swath of Northern Virginia and gets about half of its water from the Potomac.