Panel: Rocket Fuel Chemical in Water Is Safe
Experts Conclude Higher Perchlorate Levels Not Dangerous to Humans
WebMD News Archive
Jan. 11, 2005 - A chemical found in rocket fuel and present in drinking water supplies across the United States is less dangerous to humans than federal regulators had previously thought, according to a report released Tuesday by the National Research Council (NRC).
A panel of experts advising the NRC has concluded that perchlorate, a water-soluble chemical found in armaments and fireworks, is safe for human consumption at approximately 20 times the dose previously set by the Environmental Protection Agency.
While the report does not change government policy regarding perchlorate, it will play a role as EPA officials strive to set new limits on the amount of the chemical allowed in drinking water supplies.
Perchlorate has been shown to alter production of thyroid hormones in laboratory animals. The chemical prevents the thyroid gland from absorbing iodide, a critical component of thyroid hormone production.
Officials began widespread testing for perchlorate after it was found in drinking water and soil in California in the 1980s. The chemical has since been found in more than 30 states.
The EPA proposed in 2002 to limit perchlorate in drinking water to a dose of 1 part per billion. But the level was highly controversial, and the agency turned to the NRC to evaluate evidence on the dangers of perchlorate ingestion. The NRC is a private organization that was formed by Congress to advise policy makers on scientific matters.
Tuesday's report instead set a safe level for human consumption at roughly 20 times the EPA's proposal for the average adult who drinks 2 liters of water per day.
Data released in 2004 show that perchlorate contamination averages approximately 6.4 parts per billion in drinking water across the U.S., though levels in some places run as high as 200 parts per billion. Levels of 420 parts per billion have been reported in Puerto Rico, the NRC report states.
NRC experts expressed confidence that their higher limit was safe for humans because five studies had shown that humans can ingest far more than that amount in pill form each day and still see no effects on the thyroid gland.
"There was no real inhibition at this point. It was safe. It did not even invoke a biochemical change," says Richard B. Johnston, Jr., MD, a professor of pediatrics at the University of Colorado School of Medicine and chairman of the committee issuing the report.
Johnston says the committee feels its conclusions are more accurate than those reached by the EPA because the agency has relied too heavily on animal studies that showed adverse health effects at lower doses. Physicians and human toxicologists on the NRC panel were able to more faithfully evaluate studies in humans, he suggests.
"It allowed us to have more confidence in the human data than the EPA did. We did not put as much emphasis, as much confidence, in the animal data," he says.