Studies give Lake Mead clean bill of health

Wednesday, June 14, 2000 | 11:25 a.m.

Two separate studies of Nevada and Arizona infants exposed to the rocket fuel booster ammonium perchlorate did not detect any immediate ill effects from the substance draining into the Colorado River from a Las Vegas industrial complex.

Both studies concluded drinking the river's water is safe for now, but they called for more research. The issue is adding a man-made rocket fuel chemical to drinking water, scientists said.

Scientists have been concerned about possible health effects in humans since the discovery of perchlorate contaminating Lake Mead, Southern Nevada's major source of drinking water.

A scientific team led by Dr. Zili Li of Johns Hopkins School of Hygiene and Public Health, published a study of 23,305 newborns from Las Vegas and Reno to compare exposed and non-exposed newborns. The study was conducted for 15 months between April 1, 1998, and June 30, 1999.

By tracking thyroxine, a thyroid hormone in the blood, the scientists concluded that "the current study does rule out a significant effect," although they said no analysis can rule out a small effect from the exposure to perchlorate. The study was published in the Journal of Occupational and Environmental Health in February.

A similar study done in Yuma, Ariz., by Ross Brechner, chief of the Arizona Department of Health Services, reached a similar conclusion. Brechner found that mothers who drink perchlorate-laced water give birth to babies with higher levels of a hormone that stimulates the thyroid.

However, he warned, perchlorate may not have caused the difference because other possible contaminants are found in drinking water. And he did not separate the mothers who drank bottled water from those drinking tap water.

Brechner is presenting his findings to the American Water Works Association on Thursday in Denver. His study will be published later this year in the same journal as the Johns Hopkins study.

Both studies compared infants born in cities with perchlorate in the water (Las Vegas and Yuma) and those without it (Reno and Flagstaff).

Both studies urge further research.

Perchlorate, a chemical made in Henderson since the 1950s, is used in rocket fuel, fireworks, fertilizers and lubricating oils. It has been found in Lake Mead and downstream in the Colorado River all the way to Mexico, exposing about 20 million people who drink the water.

Perchlorate can slow down thyroid gland activity, potentially slowing growth. In the 1950s doctors treated people suffering from over-active thyroid glands with perchlorate.

An earlier study of perchlorate released by the U.S. Environmental Protection Agency in April showed baby laboratory rats exposed from mothers' milk led to physical differences in their thyroid glands.

Monthly measurements of perchlorate levels in Las Vegas have been made since July 1997 by the Southern Nevada Water Authority, spokesman Vince Alberta said.

During seven of the 15 months of the Johns Hopkins study, perchlorate was detected in Lake Mead's drinking water up to 15 parts per billion. That is roughly equal to a grain of salt dissolved in the water of three home swimming pools. The current perchlorate level is 11 parts per billion, Alberta said.

There is no federal or state standard for perchlorate in drinking water, although California has set a guideline limit of 18 parts per billion of the chemical.

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 and to 5 parts per billion at the Mexican border.

California was first to discover a way to detect perchlorate levels from rocket fuels at concentrations as low as 4 parts per billion.