WASHINGTON - An EPA official said yesterday there is a distinct possibility the agency will not take action to rid drinking water of a toxic rocket fuel ingredient that has contaminated public water supplies around the country.

Democratic senators called that unacceptable. They argued that states and local communities shouldn't have to bear the expense of cleansing their drinking water of perchlorate, which has been found in at least 395 sites in 35 states - or the risk of not doing so.

The toxin interferes with thyroid function and poses developmental health risks, particularly to fetuses.

Benjamin Grumbles, assistant administrator for water at the Environmental Protection Agency, told a Senate hearing that the EPA is aware that perchlorate is widespread and poses health risks.

But he said that after years of study, the EPA has yet to determine whether regulating perchlorate in drinking water would do much good.

"Is there a meaningful opportunity to reduce risk if we issue a new national regulation on perchlorate? We've been spending a lot of time on that, Madam Chairman," Grumbles told Senator Barbara Boxer, Democrat of California, chairwoman of the Environment and Public Works Committee.

"I understand your frustration in how long the process is taking, but we believe it's important to do the work," Grumbles said, promising a decision by the end of the year.

"EPA is trying to shunt the scientists to the back, put the [Department of Defense] contractors to the front," Boxer chided. "We want to see action by the scientists. We want to see a standard set."

Grumbles told Boxer it was possible that instead of a regulation, the EPA would issue a public health advisory, which would simply provide information. After the hearing he told reporters that a decision to regulate perchlorate was also still on the table.

Most perchlorate contamination resulted from Defense Department activities. The Pentagon could face huge cleanup costs if the EPA sets a national drinking water standard for the contaminant, and the department has tussled with the EPA over the issue, according to a report last week by congressional investigators.

Perchlorate is particularly widespread in California and the Southwest, where it's been found in groundwater and in the Colorado River, a drinking water source for 20 million people. It's also been found in lettuce and other foods.

The dispute over the federal government's response has been longstanding. The EPA in 2005 issued a safety standard for the chemical of 24.5 parts per billion that was criticized as "not protective" by EPA's own Children's Health Protection Advisory Committee. The safety standard indicates what the EPA considers a safe exposure level and guides Superfund cleanups, but the agency still didn't move forward with a drinking water standard.

In absence of that, states acted on their own. In 2007, California adopted a drinking water standard of 6 parts per billion. Massachusetts has set a drinking water standard of 2 parts per billion.

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