Scientist says more studies needed on effects of perchlorate

Thursday, Oct. 5, 2000 | 9:53 a.m.

A study that shows heavy exposure to perchlorate did not harm the thyroids of young children and babies is not the last word on the effect of the rocket fuel booster on human health, the scientist who conducted the report said.

Dr. Casey Crump, an epidemiologist at the University of Washington, found that drinking water with 10 times the amount of perchlorate as Lake Mead's water showed no adverse effects in more than 150 children of northern Chile.

Scientists have been concerned about perchlorate's possible effects on humans for three years, since the chemical was found in Lake Mead, Southern Nevada's major source of drinking water, and in Colorado River water downstream, exposing about 20 million people.

Perchlorate can slow down thyroid gland activity, potentially slowing growth. It has been made in Henderson since the 1950s and, besides rocket fuel, is used in fireworks, fertilizers and lubricating oils.

Funded by perchlorate producer Kerr McGee Corp., Crump studied the health of 150 infants and small children in three towns in Chile: one where perchlorate occurred naturally in amounts 10 times those found in Lake Mead, one with perchlorate contamination similar to Lake Mead's and one with no noticeable contamination.

In the city with the high perchlorate level, Crump found thyroid hormones were actually lower in newborns than in the other two cities, though the opposite would have been expected.

"It was surprising we found no effects from that level of perchlorate," Crump told the Lake Mead Water Quality Forum meeting in Henderson. His results were published in June by the American College of Occupational and Environmental Medicine.

But the $100,000 study is not enough, Crump said. More research is needed, because previous research has found the possibility of harm to the thyroid in infants.

Two studies in Arizona and Nevada found possible ill effects of perchlorate on newborn thyroids.

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 infants. The study was conducted for 15 months between April 1, 1998 and June 30, 1999.

By tracking thyroid hormone in infant blood, scientists concluded that perchlorate exposure could have a small effect on the growth gland in babies. That study was published in the Journal of Occupational and Environmental Health in February.

Another 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 drank perchlorate-laced water gave birth to babies with higher levels of a hormone that stimulates the thyroid.

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

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.

The findings of perchlorate's effects in humans agree with two occupational studies that found no health effects from chronic exposure to breathing fumes containing perchlorate.