Tuesday, Jan. 11, 2005 | 11:07 a.m.
WASHINGTON -- The rocket fuel chemical perchlorate can be consumed in amounts roughly 20 times what the federal government has said was safe, according to a new National Academy of Sciences report.
The Environmental Protection Agency in a 2002 risk assessment said people should not ingest more than .00003 milligrams per kilogram of body fat per day. But the new study said 0.0007 was safe, even for the most vulnerable populations -- pregnant mothers, fetuses and infants.
The EPA's risk assessment included a recommendation for a one part per billion standard for drinking water, which had worried Southern Nevada officials because water tested last year in Lake Mead contained an average five parts per billion of perchlorate.
The chemical leaked into the water from two Henderson chemical plants, one owned by Kerr-McGee, a Department of Defense contractor. Perchlorate was first detected in Lake Mead in 1997.
Kerr McGee stopped making perchlorate in 1998 and a cleanup project began in 1999. The other plant, owned by American Pacific, moved to Utah in 1989.
The NAS report makes no recommendation about a specific drinking water standard, and leaves that to local policy-makers.
But the Academy's recommendation on total daily dosage from all sources, including food, is considerably higher than what the EPA recommended. So the new report could be viewed as welcome news to people in Southern Nevada, said Rick Corley, a staff scientist at Pacific Northwest National Laboratory in Richland, Wa.
"There is a lot of confidence in this level, and if this dose level is protecting even those most vulnerable populations, then we are protecting the rest of the population," Corley said.
The report offers a solid foundation for the Environmental Protection Agency as it continues an effort to set a scientifically defensible drinking water standard for perchlorate, J.C. Davis, spokesman for the Southern Nevada Water Authority, said.
"This is definitely not the end of the road but a very important first step," he said. "This moves us one step closer to an enforceable standard."
The Nevada State Bureau of Health will not create its own drinking water standard for perchlorate until the federal standard is made, a practice followed by most other states, said Todd Croft with Nevada Division of Environmental Protection.
Croft's agency set an interim limit of 18 parts per billion that would stimulate cleanup and is used as a benchmark to measure cleanup progress.
Croft said the new report will be helpful in developing the national standard but will have no effect on the cleanup efforts at Lake Mead.
"The cleanup will not stop until we are satisfied the level perchlorate has been removed to protect public health," said Croft, who oversees the Kerr-McGee and America Pacific clean-up programs.
The cleanup could take decades to complete, Croft said.
Perchlorate, most commonly found as a component of rocket fuel and fireworks, in high doses can decrease the body's ability to regulate thyroid. That can cause health problems, including hypothyroidism, or possibly thyroid tumors, the EPA has said.
The chemical has been found in ground and surface waters in 35 states, prompting widespread public concern in recent years about drinking water and food supply safety.
More than 11 million people have perchlorate in their drinking water at 4 parts per billion or higher, the Academy said.
In Henderson, the Kerr-McGee plant is still overseeing a massive, multi-million dollar cleanup and water filtering project to continue to reduce the amount of perchlorate found in the Lake Mead.
Lake Mead has seen decreasing levels of perchlorate, from 14 parts per billion in 2000, to 10 parts in 2002, and nine parts in 2003.
But officials have worried that the Lake Mead perchlorate has potentially broad impact. The chemical threatened drinking water for up to 20 million residents of Southern Nevada, California and Arizona, Sen. Dianne Feinstein, D-Calif., has said.
Meanwhile Monday, a leading environmental group charged that the Bush administration conspired to "twist the science" to avoid government and Defense Department contractor responsibility in clean-up efforts.
The National Resources Defense Council obtained 30 boxes of documents from the federal government after filing Freedom of Information requests, and eventually, a lawsuit, that the group says proves the Bush administration sought to influence the National Academy. The documents show an "uncommon, extensive" effort by the White House and Pentagon to limit the scope of study by the typically above-reproach Academy, the group alleges.
An Academy spokesman dismissed allegations of report bias, however. The congressionally chartered National Academy is generally regarded for highly independent, blue ribbon research panels. Scientists are routinely vetted for conflicts of interest.
"The government did not influence our committee or the outcome of our report," spokesman Bill Kearney said. "The Academy operates independent from the federal government."
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