The government yesterday issued its first safety standard for perchlorate, a toxic chemical used in rocket fuel and explosives that has been blamed for widespread contamination of drinking water, especially near many military sites.
The Environmental Protection Agency's limit for what the agency considers safe exposure will be used in guiding Superfund cleanups and determining whether the agency should go a step further and regulate perchlorate as a drinking-water contaminant.
The limit, which translates to 24.5 parts per billion in drinking water, is what the National Academy of Sciences recommended in January but is higher than the EPA proposed two years ago.
Perchlorate is a chemical found in nature, but the academy said its presence in the environment is mainly from its use in rocket fuels, fireworks and explosives. It has been linked to thyroid ailments and is considered particularly dangerous to children.
"This reference dose is protective for all populations including the most sensitive," EPA spokeswoman Cynthia Bergman said.
The EPA issued a preliminary recommendation two years ago for an exposure level that translated into 1 part per billion. The Pentagon criticized that as too stringent.
Erik D. Olson, a lawyer with the Natural Resources Defense Council, said the exposure level the EPA considers safe is too lenient to protect those most vulnerable -- infants and pregnant women.
The standard, if used as a benchmark for cleaning up Superfund and military sites, "really puts potentially hundreds of thousands, if not millions, at risk," Olson said.
States and local governments have been trying to get defense contractors and the Pentagon to pay for the huge costs of removing the chemical from groundwater. California and Massachusetts have proposed limits on perchlorate contamination far more restrictive than the level the EPA chose.