Snyder's initial findings about the source of the problem were inconclusive. But understandably disturbed by the situation, the Southern Nevada Water Authority in 2000 hired Snyder as its research and development director. Since then, he and fellow scientists have confirmed that natural and synthetic chemicals in Lake Mead are deforming some fish and disrupting their capacity to reproduce.
The culprit isn't factory discharges or polluted runoff from farms. Rather, it's the 1.8 million metro area residents and 38 million tourists who visit the city annually. Every day, the pharmaceuticals, personal care products and human hormones they secrete or rinse from their bodies are flushed down the drain. Those substances accumulate in the sewage effluent that Las Vegas releases into the reservoir behind Hoover Dam.
For Nevada's water agencies, as well as those in big cities in California and Arizona, the question now is whether these newly detected "emerging contaminants" pose any danger to the millions of people who drink water from the Colorado River.
The country has 53,000 drinking-water systems, and most have all they can handle ensuring an adequate supply for growing populations, coming up with billions of dollars to upgrade sewage treatment plants and installing expensive new technology to ensure that water flowing through household taps will meet existing federal contaminant limits. But a handful of water utilities are on the forefront of scientific research to determine whether they'll also need to deal with thousands of additional substances that are showing up in increasingly sophisticated water-quality tests.
FEMINIZED FISH
In the mid-1990s, fishermen in Great Britain recognized that downstream from aging sewage-treatment plants all the fish they caught had female organs. Meanwhile, herpetologists found that male alligators and frogs exposed to pesticides were also developing female characteristics. More recently, researchers have found feminized fish in wastewater effluent in the Potomac River outside Washington, D.C., near Denver and in the Pacific Ocean just offshore from Los Angeles and Orange County, California.It's clear that chemicals discharged into the environment can alter some organisms' endocrine systems, which secrete hormones into the bloodstream to control reproduction, growth and development. Congress has responded by ordering the U.S. Environmental Protection Agency to start reviewing whether endocrine-disrupting chemicals also threaten human health. Federal regulators have proposed limits on perchlorate, a compound from rocket fuel known to affect endocrine glands, but EPA's review of thousands of pesticides, plastics and other commonly used compounds is dragging on.
At the same time, concern has emerged that frequently prescribed pharmaceuticals and ubiquitous personal care products such as soap, shampoo and detergents could be causing similar environmental damage. Increasingly accurate laboratory technology makes it possible to identify much smaller chemical residues, down to minuscule parts-per- trillion levels, in sewage effluent and drinking-water samples. "Birth-control pills have been around since the 1960s, but now we are actually able to detect them at these lower concentrations," notes Joe Gully, an environmental scientist for the Los Angeles County Sewer District's ocean research program.
Meanwhile, Snyder and others have documented that Las Vegas' treated sewage plant discharges carry traces of codeine, Prozac, Valium, common antibiotics, insect repellents and a host of chemicals termed endocrine disruptors into the Lake Mead reservoir. And they have linked those human byproducts to abnormal female characteristics in carp, bass and razorback suckers, which swim and feed in the effluent the city's treatment plants release into the lake.
So far, the results have detected "essentially no human health concern," according to Snyder. But the National Park Service manages a national recreation area along the lake, and Los Angeles, San Diego, Phoenix and Tucson draw much of their supplies from the Colorado River reservoir. "It's a really politically motivated body of water," he adds, and downstream residents naturally recoil at the thought that they're unwittingly ingesting somebody else's medicine.
So water and sewer utilities feel compelled to follow up on even cursory findings that drugs, chemical residues and even natural human hormones flowing through municipal sewers are disrupting reproduction in fish that swim downstream. With the science so uncertain, local officials worry that the U.S. Environmental Protection Agency will eventually feel compelled to order communities to install expensive treatment upgrades to dispel the public's fear that emerging contaminants pose similar threats to human health.
DON'T FLUSH
As the data accumulates, governments in some areas are taking steps to give patients alternatives to flushing unused prescription drugs down their toilets. Three years ago, psychiatrists persuaded the Maine Legislature to provide prepaid envelopes for mailing drugs past their expiration dates to the state's drug enforcement program for safe disposal. Chicago has experimented with drug-return programs, and Washington State this summer launched a pilot collection effort giving consumers a way to drop off unused medications at drugstores. But pharmaceuticals also leach from landfills and seep into streams in animal waste from feedlots where livestock are fattened. And as millions of Americans take their medicine every day, they're also passing residues through their bodies into community sewer systems.The pharmaceutical byproduct stream is renewed daily, and the volume is growing as doctors prescribe new drugs that go on the market. In addition, even the healthiest people excrete some of the natural hormones their bodies produce, and more of those are flowing into wastewater systems as urban populations expand. The levels of natural estrogen in Las Vegas' wastewater is 10 times higher than synthetic estrogen used to make birth-control pills, Snyder points out. "There's not much we can do about that; it's not like an industrial chemical that you can ban or restrict."
Most studies that detected damage to aquatic life haven't demonstrated that sexual deformities are widespread enough to threaten entire populations of fish or amphibians. In Lake Mead, however, a 2002 U.S. Geological Survey study warned that sexual deformities conceivably could decimate the razorback sucker, an endangered species that tends to concentrate near Las Vegas' sewage outfall to feed on nutrients in the effluent. The Clark County Water Reclamation District is considering spending $585 million on a 17-mile-long pipeline that would pump most of Las Vegas' 170 million gallons of effluent per day to be diluted in 250-foot-deep waters above Hoover Dam. Biologists, however, worry that approach would send emerging contaminants over the dam, threatening Colorado River fish populations along the Arizona- California border.
Snyder's research has found that treating effluent with ozone or reverse osmosis can remove more than 70 percent of most suspected pharmaceutical and endocrine-disrupting contaminants. However, he notes, "the cost of implementing those types of processes can be enormous."
In contrast to well-documented threats such as Cryptosporidium or water-treatment byproducts, "I haven't seen any compelling evidence that emerging contaminants in drinking water" are harming people who drink it, Snyder says. Pharmaceuticals are commonly used to stimulate livestock growth and milk production, "and people get a much greater dose from eating a steak or drinking milk."
TREATMENT TACTICS
Snyder now is working with the American Water Works Association and some of California's biggest water-supply systems on a project that is studying what kind of treatment most effectively removes 15 widely used pharmaceuticals and eight suspected endocrine disruptors that have been found in drinking-water supplies. Environmental groups keep prodding EPA to move more quickly to identify and control emerging contaminants, and state and local governments are well aware that regulations could eventually be imposed.The Pennsylvania Environmental Protection Department and USGS have started screening streams and groundwater for unregulated contaminants, and the Philadelphia Water Department continues monitoring its supply after studies two years ago found minor traces, measuring in the parts per trillion, of 13 painkillers, antibiotics, antidepressants and other drugs, as well as estrogen and the insect repellent DEET in the city's water.
Christopher S. Crockett, Philadelphia's watershed protection manager, sees no risk to city residents but acknowledges that press accounts of the research have caused public concern. Philadelphia draws water from the Schuylkill and Delaware River basins, and "5 percent of the U.S. population lives in our watershed," he says. Most city residents nonetheless don't understand that "not all the water comes from the top of the Rocky Mountains," so learning that tap water carries minute amounts of hormones and pharmaceuticals that have passed through upstream residents' bodies "is really shocking to a lot of people."
Negative public reaction could be even more worrisome for water-short Southwestern cities that share the Colorado River's overcommitted supply. Fast-growing desert cities are counting on expanding their resources by recycling sewage effluent for irrigating golf courses and eventually replenishing drinking-water supplies. Studies led by Gully, the Los Angeles County researcher, suggest a possible solution: Let treated effluent trickle through layers of soil. This appears to effectively remove estrogen from the wastewater that California and Arizona cities have begun using to recharge groundwater aquifers to replenish drinking-water reserves. While there's no evidence that the water is dangerous for drinking, "it's part of our mission to make sure our water is safe for reuse," Gully says. "This is a really new field, and it's one that's worthy of investigation."
