HENDERSON, Nev. - Thirty miles south of the glittering Las Vegas Strip, the soot-covered Kerr-McGee chemical plant stands quietly behind an impenetrable row of tall evergreen shrubs. The plant sits on the edge of the tamarisk-choked Las Vegas Wash, a desert waterway that drains into Lake Mead.

Built during World War II to produce magnesium for artillery, airplanes and ships, the drab-colored factory was converted in 1952 to produce ammonium perchlorate, a component of rocket fuel. Kerr-McGee, an energy and chemical manufacturer based in Oklahoma City, hasn't made perchlorate at the plant since 1998, but downstream water users are now grappling with the fallout from the plant's production years. In 1997, water officials discovered that the factory is releasing a plume of perchlorate into the wash, which then seeps into Lake Mead and the Colorado River - the drinking-water source for Las Vegas and 21 million people downstream in California and Arizona.

When the leak was first discovered, perchlorate concentrations were as high as 60 times what the U.S. Environmental Protection Agency now considers safe. Some researchers believe that even small doses of the pollutant can cause thyroid imbalances that lead to developmental problems in fetuses and young children.

It's a bad time to deal with tainted water: Drought is stretching water supplies in the West, and Southern California is grappling with a federally imposed 15 percent reduction in its use of the Colorado River (HCN, 1/20/03: California’s water binge skids to a halt). But as officials work to clean up the problem at Kerr-McGee, perchlorate, which is also used in road flares, dry cleaning, airbag inflators and medication for thyroid disorders, is turning up in more and more places - and may even be showing up in salads across the country.

"It is really one of the most massive pollution problems the water industry has ever seen," says Timothy Brick with the giant Metropolitan Water District of Southern California.

The bad stuff

Although the health effects of perchlorate in drinking water are still largely unknown, there's plenty of cause for concern. Ammonium perchlorate is used to treat people whose bodies produce too much thyroid hormone. But Renee Sharp, an analyst with the Washington, D.C.-based scientific research organization Environmental Working Group, says that fetuses and young children who receive trace exposures of perchlorate are susceptible to disrupted brain development and decreased IQ. "More significant exposures can lead to mental retardation, deafism and mutism," she says.

The EPA acknowledges perchlorate is a potential health problem, but says "uncertainties in the toxicological database" stand in the way of knowing how great a threat it actually poses. The agency currently has a nonenforceable "provisional reference dose" of 4 to 18 parts per billion (ppb). A single part per billion is roughly equivalent to one drop of water in an Olympic-size swimming pool. But according to Kevin Mayer, the EPA's regional perchlorate coordinator, the current definition is not "clear-cut." The agency has twice delayed a comprehensive study and has now asked the National Academy of Sciences to step in as an external review committee.

Perchlorate concentrations in Lake Mead are currently 8 to 15 ppb. In the Colorado River below Hoover Dam, they range from 5 to 15 ppb.

Mark Beuhler, Metropolitan's associate vice president, says that his agency is protecting its customers by blending Colorado River water with perchlorate-free water from Northern California. This dilutes the pollutant to below four ppb, the "action level" set by the California Department of Health Services.

Gina Solomon, a Natural Resources Defense Council health expert, argues that the EPA's target should be lower. "The more we know about perchlorate, the more concerned we get," says Solomon. "The science suggests that very low doses can affect the thyroid, which then interferes with brain development."

A widening circle

The problem isn't limited to the Colorado River: Perchlorate is popping up in hundreds of groundwater wells throughout the West. In 2000, New Mexico officials detected traces of the chemical in wells near the U.S. Department of Energy's Los Alamos National Laboratory.

John Kemmerer, the deputy director of the EPA's Superfund program in San Francisco, says that perchlorate has contaminated almost 200 drinking water supplies throughout California. His office is overseeing a $111 million effort to clean up a contaminated aquifer beneath the Aerojet Superfund Site near Sacramento, an effort that may take 240 years. Perchlorate contamination below California's San Gabriel Valley has spurred one of the largest groundwater cleanup projects ever proposed under the Superfund program, projected to cost $320 million.

But the perchlorate threat may reach far beyond drinking water, turning up in vegetables irrigated with Colorado River water.

"Between November and March, as much as 90 percent of the nation's lettuce is grown in California's Imperial Valley," says the Environmental Working Group's Sharp. "Perchlorate contamination could potentially become a widespread health problem throughout the nation."

Studies indicate that plants can accumulate perchlorate in their cells at much higher levels than appear in the water used to irrigate them. A 1997 study of vegetables grown with perchlorate-laced water in San Bernardino found perchlorate concentrations thousands of times higher than what the EPA considers to be safe.

In Las Vegas, Kerr-McGee is working to clean up the contamination. In 1998, the company began building a system of 34 extraction wells and two "ion exchange" devices to remove perchlorate from the water, and it now trucks dozens of giant bags filled with the sand-like byproduct of ion exchange to an incinerator in Utah each week.

But the cleanup hasn't been cheap: So far, Kerr-McGee has spent over $61 million. In 2000, Kerr-McGee filed a lawsuit against the Navy, which owned and oversaw the plant for nearly 10 years, claiming that the military should share the expense. Now, however, the Pentagon is pushing for nationwide exemptions from cleanup liability (see story at left).

The author writes from Springdale, Utah.



    You can contact ...

    Kerr-McGee, Debbie Schramm, 405/270-2877, www.kerr-mcgee.com;

    Metropolitan Water District, Bob Muir, 213/217-6930, www.mwd.dst.ca.us;

    Environmental Working Group, Renee Sharp, 510/444-0974, www.ewg.org/reports/rocketlettuce.