A recent survey of bass in the Potomac River, a major tributary in the nation's capital, found almost 100 percent of the smallmouth bass species were feminized, or had eggs in their testes. In largemouth bass the incidence of feminization was lower, but still highly prevalent.

Although some fish species are true hermaphrodites and change sex throughout their lives, bass should be only one sex, said Vicki Blazer, a fish pathologist at the U.S. Geological Survey.

A motley assortment of chemicals, pollutants containing hormones and estrogen-like compounds are likely the culprit for the irregularities in these "intersex" fish. Such substances are called "endocrine disruptors," as they can mimic estrogen's role in the body or can affect enzymes that produce sex hormones.

In the intersex bass, the males still produce sperm, and the eggs are only seen through the microscope. Blazer plans to study bass behavior in 2007 to see if these physical changes are affecting the reproduction of the fish.

The exact chemicals to blame for the spate of intersex bass in the Potomac are unknown, although analyses are under way.

Likewise, no one knows if the pollutants are in drinking water and how they could harm human health.

"It's not something we need to panic about, but it's certainly a concern," Blazer said.

People in sensitive life stages, such as children, may be a more urgent target for research, Blazer added. Young fish seem to be more affected by endocrine-disrupting chemicals. Fish have very similar bodies, organs and immune systems to people, so it may or may not be logical to believe humans are similarly influenced, Blazer said.

Since 1996 the U.S. Environmental Protection Agency has led a research effort to develop screening tests for detecting the endocrine disruptors in water, as well as investigate the effects of the pollutants on people and wildlife.

The agency is working to determine what constitutes an "unreasonable risk" for people, said Dr. Elaine Francis, the national program director for the EPA's Pesticides and Toxics Research Program.

The EPA's office of research and development has consistently named endocrine disruptors one of the agency's six highest priorities.

The agency conducts research in its laboratories, as well as issues grants to university scientists to study endocrine disruptors in the environment.

For instance, some EPA-funded researchers are surveying waterways downstream from sewage treatment plants and animal feeding operations.

Many of the grantees have found evidence of intersex fish, as well as a high prevalence of endocrine-disrupting chemicals in sites throughout the country.

Intersex fish have been identified worldwide, from the Colorado River to ocean waters off southern California to rivers in the United Kingdom and Japan.

Blazer has begun the frustrating task of trying to find an unpolluted, pristine river -- essentially, a control group -- to compare to the male fish in the Potomac. But she's found even in the deep mountains of West Virginia, the rivers still contain pollutants.

Without a comparison, Blazer isn't sure if bass are more susceptible to these pollutants than other fish. She also doesn't know which chemicals are causing the most damage.

Dana Kolpin, a USGS research hydrologist in Iowa City, Iowa, works in the agency's emerging contaminants project, and he's helping Blazer to test Potomac water samples. To get down to small parts per trillion levels, Kolpin uses sophisticated laboratory tools.

By focusing on why compounds exist in an area, and how they travel through waterways and groundwater, Kolpin provides data for regulatory agencies, such as the EPA, to make policy decisions.

But linking a specific compound to an outcome -- that "smoking gun" -- gets complicated, especially when there is a mix of chemicals in the water. In one study Kolpin found 40 compounds in a single stream, not including pesticides.

Some evidence has suggested the chemicals also have a cumulative effect -- at low concentrations, it might take a month or two for the fish to be affected.

Kolpin examines a multitude of chemicals considered emerging contaminants, and some of the most egregious offenders are pills, which may also contain estrogen-like compounds. Drugs provide immeasurable benefits to human health, but there may be a downside, he said. Consumers get little guidance as to how to dispose of unused medication.

Leftover pills flushed down the toilet end up in the sewage system, and medication thrown in landfills could leach into groundwater. Sediments in riverbeds are also highly concentrated areas of emerging contaminant pollution.

And of course, there's the anti-microbial soaps, toothpaste, the musk used in fragrances, sunscreen, even caffeine -- the American lifestyle of materialism has left an indelible impression on U.S. waterways, and no one knows the exact repercussions.

Kolpin believes emerging contaminants, such as endocrine disruptors, will become more and more of a public concern.

"If you're finding ibuprofen or things you take in on an everyday basis (in your water), it hits home," he said.

Related Links
Our Polluted World and Cleaning It Up
Water, Water Everywhere and Not A Drop To Drink...