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In a stretch of the lower Colorado River below Lake Mead, wildlife biologists are worried that fish are losing their gender. Chemical-laced wastewater, they fear, is giving fish what amounts to a sex change.
The phenomenon, called gender-bending, has already shown up in fish nearby, in the Las Vegas area, where skewed hormone levels in the water have left scientists wondering if the fish can reproduce normally. While the females seem to be doing fine -- in fact, producing more eggs than usual -- the males have become more feminine, with increased levels of estrogen, smaller sex organs and weaker sperm. It's almost as if the males were being altered by taking the birth control pill.
To some degree, they are.
Fish in Las Vegas Wash live in streamflows that consist mainly of treated wastewater and urban run-off that spews south from Vegas. There, fish are ingesting chemical traces of birth control pills and other pharmaceutical residues found in human waste, along with remnants of rocket fuel from a nearby industrial plant and musks from perfumes, shampoos and other personal care items that end up getting washed down Vegas' drains.
The chemicals can compromise the reproductive systems of wildlife, scientists point out, in a process called endocrine disruption. But despite the environmental threat posed by the toxic run-off, none of the compounds are filtered out by wastewater treatment plants or even regulated by the Environmental Protection Agency.
The result: fish that have become the gender-twisted product of human waste.
Several miles downstream, past Lake Mead and across the Arizona border, scientists are wondering if fish here could be going through gender-bending as well. Arizona has the same potential for contamination, with its own wastewater treatment plants emptying into rivers. The state even has the same species of endangered fish, the razorback sucker, struggling to survive here. But that struggle could get a lot harder if the species starts showing signs of sexual dysfunction; hormonal imbalances have already been detected in razorback suckers in Nevada.
To check on the sexual health of fish in Arizona, the U.S. Fish and Wildlife Service is seeking government funding for a $208,441 study of razorback suckers and carp at two of the four wildlife refuges the service manages in the area, including Cibola National Wildlife Refuge and another refuge to be named later. The study, which officials say has a good chance of receiving federal funding, would be the first of its kind in Arizona.
Biologists suspect that fish are already experiencing endocrine disruption all along the lower Colorado, where chemicals from wastewater treatment plants in Bullhead City, Lake Havasu City and Blythe, as well as agricultural and storm run-off, could be altering hormone levels and shrinking gonads in fish. Eventually, Fish and Wildlife biologists would like to extend their studies to the Gila River south of Phoenix, where urban run-off is probably more toxic and more likely to be emasculating male fish.
The disfigurement may seem bizarre, but it shouldn't come as a surprise, scientists say. Unlike contamination from a chemical spill, exposure to endocrine-disrupting chemicals is no accident. With the pharmaceutical industry feeding America's dependence on prescription drugs with ever more medications, it's only natural that our wastewater would be increasingly tainted by the chemicals we ingest. The same goes for perfumes and shampoos that wash off our bodies and down the drain.
"We just didn't know to look for these compounds," says Erik Orsak, a contaminant specialist for Fish and Wildlife in Nevada. "Our chemistry has improved, and sure enough, we're finding things we never found before."
With wastewater treatment plants across the country releasing these chemicals, scientists believe wildlife in every waterway downstream of a treatment plant is immersed in this toxic cocktail. Las Vegas and Phoenix are some of the first cities to begin looking for the pollutants and their effects on animals.
But what about their effects on humans? Could exposure to endocrine-disrupting chemicals be blamed for problems some couples have getting pregnant? It's too soon to say, according to scientists, who are still trying to determine if certain animal populations have been hurt by gender-bending. Studies have shown that spills of these chemicals have altered hormone levels in humans and animals that were directly exposed in high doses, but the effects of low-level exposure remain controversial. Critics claim that many other factors could be causing sex-related problems.
Nonetheless, public paranoia runs high.
In Nevada, where findings of fish disfigurement were first released in 1995, the reaction was torrential. Tourism officials worried that the study would scare off visitors, and water authorities tried to fight off fears over water quality, which they maintain has not been compromised.
"There were efforts to discredit the work [of the 1995 study] that were not successful," says Hugh Bevans, now district chief of the U.S. Geological Survey in West Virginia, who started the Nevada fish study. "People looked at us as muckrakers, and maybe we are muckrakers, but as professional scientists in water quality, that's your job."
Eventually the outcry calmed down, but it has not faded away entirely. Today, as Las Vegas' exploding population shoots out more and more wastewater, eroding the Las Vegas Wash, water managers are looking into ways to divert the wash out of the crumbling channel and away from the community's drinking water supply downstream in Lake Mead.
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