Chemical reading hits high mark at lake

Thursday, Nov. 30, 2000 | 11:27 a.m.

The Southern Nevada Water Authority today reported the highest level of perchlorate, a rocket fuel booster, ever recorded in Lake Mead.

Although there is no state or federal limit for perchlorate in drinking water, studies are trying to determine if perchlorate, produced since the 1950s at two Henderson industrial plants, harms human development.

In August 1997 the Nevada Division of Environmental Protection ordered the water authority to report any perchlorate above 18 parts per billion. That is the limit established by California water officials after they discovered a test to measure such small amounts.

The recent readings at the intake pipe where the Las Vegas Valley gets its drinking water have ranged as high as 6 part per billion over the recommended reporting level.

Scientists belive that perchlorate finds its way from the Henderson plants into Lake Mead through ground water running into the Las Vegas Wash.

The chemical salt has been found in a plume of pollution in the lake. The recent high readings occurred because warmer weather has allowed the plume to sink to the level of the pipe, water authority scientist Peggy Roefer said.

The average amount of perchlorate at the drinking water pipeline was 17.6 parts per billion in November. Five water samples collected during the month ranged from 11 to 24 parts per billion. The 24 parts were confirmed Monday, water authority spokesman Vince Alberta said.

However, overall perchlorate levels in Lake Mead are dropping, Alberta said.

Researchers fear that perchlorate in drinking water could affect thyroid growth in children.

Perchlorate is not listed as a hazard by the Environmental Protection Agency, but the chemical is a candidate for the federal hazardous list.

Numerous studies, including a controversial one at Loma Linda University Medical Center in California with 100 human volunteers, are under way.

Two previous research efforts looked at people who drank water with and without perchlorate in it. The results were inconclusive, although one study suggested Arizona infants' thyroids may have been affected by the perchlorate.

California scientists first detected perchlorate in 1997 in Lake Mead.

Perchlorate has been discovered in water in 15 states from New York to California. The salt is found in rocket fuel, fertilizers and fireworks.

In the 1950s doctors gave high doses of perchlorate to people with overactive thyroids, but effects from chronic low doses in drinking water are unknown at this time.