Study: Perchlorate no human threat

Thursday, Jan. 14, 1999 | 11:23 a.m.

Perchlorate, a salt used to enhance rocket fuel which has been detected in Lake Mead water, alters thyroid activity in animals at high doses, but in people who inhaled it, there were no immediate effects, the first of recent studies on the chemical shows.

The study has been highly anticipated for more than a year after researchers discovered widespread ammonium perchlorate contamination in Lake Mead, Southern Nevada's major drinking water source, in 1997.

The Lake Mead contamination was caused by two plants manufacturing ammonium perchlorate since the 1950s. Fourteen other states have found perchlorate in ground water and drinking water supplies.

The 250-page draft report recommends a "reference dose" of 32 parts per billion of perchlorate in water for a 154-pound man as a starting point for research. The research should eventually set a safe standard for levels of perchlorate in water.

California has already set a guideline of 18 parts per billion. The highest level of perchlorate in Las Vegas was recorded at 16 parts per billion in a reservoir located in the western area of the valley.

The EPA published the study in the Federal Register today. The next step is peer review, in which other scientists evaluate the validity of the research.

Allen Biaggi, Nevada Division of Environmental Protection administrator, said it would take years for the EPA to set a standard for perchlorate.

In one part of yearlong study, led by the EPA's National Center for Environmental Assessment, employees at Kerr-McGee Chemical Corp., the remaining manufacturing plant of the chemical near Henderson, inhaled about 1 milligram per day of ammonium perchlorate as dust to study acute effects.

Researchers concluded that the workers' thyroids were operating properly at the end of the shift.

No details of the number of workers who participated were available, and scientists predicted no change to the employees in 10 years. No reason was given for that prediction.

However, perchlorate, as a salt, dissolves in water and may not show effects from being inhaled, earlier studies of the chemical have shown.

In a second part of the study, rats, mice and pregnant rabbits were given perchlorate in their water.

The rats showed "significant changes in thyroid hormones" at a dose of 350 parts per billion.

The EPA report concluded, however, that the study and other so far "produce no evidence that perchlorate affects reproductive function, causes birth defects, alters the behavioral development of young animals, or causes mutations or DNA damage."

Interestingly, perchlorate was given to humans in pills and water in Europe in the 1950s to control hypothyroidism -- overactive glands. Very high doses caused blood diseases and some deaths.

Nevada plans to continue requiring perchlorate cleanup in Henderson to stop the chemical from entering Lake Mead, officials said.