Perchlorate findings concern scientists

Monday, April 24, 2000 | 11:23 a.m.

A new discovery of the effect of perchlorate on baby laboratory rats now has scientists trying to determine whether the chemical found in Southern Nevada drinking water might affect human growth.

The effect of even the small doses involved in the new research concerned scientists. Preliminary findings showed that baby rats exposed to the chemical through their mother's milk had physical differences in their thyroids, which control growth, Kevin Meyer, a toxic expert at EPA's San Francisco office, told a group of scientists at UNLV on Friday.

"We thought this would be a no-effect dose," Meyer said. "We saw an effect, but it is very preliminary."

That has scientists now looking at whether low doses of perchlorate consumed by drinking roughly two quarts of water a day interferes with human growth, he said.

"With enough perchlorate in the water, you can keep a tadpole from turning into a frog, so it can disrupt development," Meyer said.

Perchlorate, a chemical made in Henderson used in rocket fuel, fireworks, fertilizers and lubricating oils, has been found in Lake Mead, which supplies Southern Nevada's drinking water, and in Colorado River water all the way to Mexico.

A team of federal, state and university researchers will study people in Las Vegas, Los Angeles and Sacramento, where perchlorate has been discovered in drinking water supplies, and compare them to residents who drink water without the chemical.

Perchlorate is not listed as a hazard by the EPA, Meyer said, but the chemical is a candidate for the hazardous list.

The laboratory rat study raises a concern about exposing infants and children to perchlorate, which moves easily in water and stays in the environment.

While perchlorate has been found as high as 1,000 parts per billion in the Las Vegas Wash, the Colorado River's volume reduces the chemical to about 9 parts per billion in Lake Mead, which supplies Clark County's drinking water, and to 5 parts per billion at the Mexican border.

UNLV engineering professor Jacimaria Batista and her colleague, Roshan Boralessa, found in an ongoing study that perchlorate levels in the Las Vegas Wash have stayed the same since 1993. "The results mean that it has been there a long time," Batista said.

Kerr-McGee Chemical Corp. started producing perchlorate in Henderson in 1945 and American Pacific, formerly Pacific Engineering & Production Co., produced the chemical in Henderson from 1958 until explosions and fire leveled its plant in 1988.

Kerr-McGee is spending $500,000 a month to remove perchlorate from ground water flowing from its operating plant at the rate of 400 gallons per minute, Meyer said. The company plans to use microbes to treat the water.

That may not solve the entire problem. Researchers have found perchlorate in the soils and the wash itself.

While it will take years for the federal government to set a safe drinking water limit, Meyer said states are not waiting. In August 1997 Nevada adopted an 18 parts per billion limit, California's standard, after discovering perchlorate in Lake Mead. The highest reading in the lake was 16 parts per billion.

Arizona caps perchlorate at 32 parts per billion and Texas at 22.

Perchlorate has been discovered in 15 states from New York to California, Meyer said. "I'd say it is a nationwide problem," he said, explaining that wherever space shuttle engines are flushed out, perchlorate contamination has followed in wells.

Meyer said the EPA also suspects people may be exposed to perchlorate through eating food grown with contaminated water or inhaling contaminated dust.

One piece of good news, EPA Las Vegas laboratory scientist Mark Rigas noted, is that skin protects people from perchlorate exposure. "It's not going to dissolve through the skin," he said.

Congress spent $3 million on preliminary studies of perchlorate in animals last year, Meyer said. The U.S. Air Force is asking Congress for $3 million a year over three years to study technology to treat perchlorate in drinking water.

Treatment can use microbes to convert perchlorate to oxygen and chloride as Kerr-McGee plans to do, or an ion exchange in which the perchlorate is replaced by chloride.

Mary Manning covers environmental issues for the Sun. She can be reached at (702) 259-4065 or by e-mail at manning@lasvegassun.com.