Male fish becoming female?

Researchers in Colorado have made a startling discovery. Fish, apparently male, are developing female sexual organs. Scientists believe it's the result of too much estrogen in the water and they're finding estrogen in rivers across the country.

In Colorado's rivers and streams, scientists are waist-deep in ritual of the season, using electric currents to stun native fish to the surface where they're measured and checked. But what they discovered in the white sucker fish has got even veteran scientists concerned.

"I've done a lot of studies throughout my career which extends back to 1973," says research associate John Woodling. “This is the very first time that what I've found scared me."

"This fish has characteristics of both male and female," says Dr. David O. Norris of the University of Colorado, Boulder.

And scientists have found lots of them in three Colorado rivers, all of them downstream from sewage treatment plants.

In the Boulder Creek, female white suckers outnumbered males five to one and 50 percent of the males also had female sex tissue.

Researchers say the cause is too much estrogen in the water, a natural female hormone that is found in every sewer system. But also, they say, certain chemical compounds in detergents and soaps can mimic estrogen.

Barbara Biggs, of Denver's largest sewage plant, says most of the nation's sewage plants simply can't remove all the estrogen in the water.

"We're concerned about the effect on aquatic life, but we're also concerned about our ability to actually treat for these estrogens and estrogen mimickers," says Biggs.

Estrogen mimickers are believed to be caused by chemicals called nonylphenols, found in everything from paints and rubber to cosmetics and plastics. They are considered a possible cause of kidney, eye, liver and reproductive problems. 

They’ve been banned in much of Europe and are under review in Canada, but are still common in America, where they are flowing out of sewage plants and into clean water flowing into America's rivers.

Government researchers recently found natural estrogens and estrogen mimickers in 80 percent of the streams they tested in 30 states.

"We would be ingesting those chemicals, would absorb them, and they would add to whatever natural hormones we already have in the body," says Dr. Norris.

No one is certain what the impact is on humans. But since finding evidence that estrogen may be turning male fish into female fish, scientists are now looking at what it means for the nation's drinking water.

In a state that prides itself on living in harmony with nature, this is evidence, say researchers, of a hormonal imbalance.