(NaturalNews) More than 80 percent of male bass in the Potomac River on the U.S. Atlantic coast are producing eggs or showing other female traits, the nonprofit Potomac Conservancy has warned, in a call for more research into the causes of intersex fish.
In a recent U.S. Geological Survey (USGS) report, intersex fish were found in a third of all 111 sites tested across the United States, including in major waterways such as the Mississippi River and the Rio Grande. The phenomenon occurred in 16 different species, but was most common in male smallmouth and largemouth bass.
Researchers agree that the phenomenon is almost certainly caused by the presence of pollutants in the water, including endocrine- (hormone) disrupting chemicals and the residue of pharmaceutical products.
"We have not been able to identify one particular chemical or one particular source," said USGS biologist Vicki Blazer. "We are still trying to get a handle on what chemicals are important."
Among the chemicals likely to be contributing to the problem, Blazer cited birth control pills and other hormone-containing drugs, antibacterial products including tissues, personal care products (especially those containing fragrances), flame retardants, pesticides and fertilizers.
"In fertilizer [and pesticides] there's natural estrogen and testosterone and other things ... so if we can hopefully pinpoint some of those mixtures or individual chemicals that then perhaps we could manage better," Blazer said.
It has been hard to narrow down the list of major contributors, however. For example, Blazer tested fish up- and downstream of sewage treatment plants to see if the factories might be major sources of endocrine-disrupting pollutants. She found no difference in rates of sexual abnormalities.
The Potomac Conservancy has called for more research into the problem.
"We've got to figure out what the heck is going on here," said the group's president, Hedrick Belin. "And we've got to figure it out sooner rather than later because it's clear the longer this mystery continues it's only going to lead to bad things yet to be discovered."
Because the hormonal systems of all vertebrates are strikingly similar, anything that has an impact on fish living in water is likely to have an effect on humans drinking it, as well. Yet figuring out the specific effects of tainted water on people may prove difficult.
"Because fish, of course, are in the water all the time," Blazer said. "But what's in your drinking water, what you might be exposed to through skin and food and everything else, is another issue for people."
Even if researchers eventually figure out which chemicals are the major contributors to sexual deformity in fish, that may shed little light on the question.
"It's going to be a lot harder to get to how these chemicals affect people because of course you can't experiment on people," Blazer said.
Approximately 4.5 million residents of the Washington D.C. area get their drinking water from the Potomac.
According to the Potomac Conservancy, individuals can help reduce watershed pollution in part by making more careful purchasing decisions. Consumers should reduce their use of toxic chemicals such as pesticides, and look for more natural cosmetics and other products.
"The chemicals that are in personal care products such as some of the antimicrobials, fragrances, are endocrine disruptors," said Blazer. "So being smart about the kinds of products you're buying -- because they are available in things that are fragrance-free, antimicrobial-free, things like that -- are things that individuals can do."
Conservancy supporter Rep. James P. Moran of Virginia has urged people to always take old or unused drugs back to a pharmacy for disposal.
"Don't flush pharmaceuticals down the toilet," he said. "They don't disappear when you flush them."
The Potomac Conservancy is also working on a campaign to get pharmaceutical technologies to dispose of drugs more safely, and calling for better water filtration technology.
"We need to get these toxins out of our river water," Belin said.