By Joby Warrick
Washington Post Staff Writer
Wednesday, March 24, 1999; Page A8

The federal government has underestimated the risk posed by arsenic in drinking water, allowing levels of the naturally occurring carcinogen that could put large numbers of Americans at risk for bladder and lung cancer, a scientific panel concluded yesterday.

The National Research Council, an arm of the National Academy of Sciences, urged the government to tighten its controls on arsenic "promptly," a move that would bring the federal standards in line with guidelines already adopted by international health organizations and recommended by U.S. regulators 37 years ago.

The recommendation makes it virtually certain that the Environmental Protection Agency will significantly strengthen the nation's 57-year-old guidelines for arsenic in coming months, imposing new costs on municipal water suppliers and possibly complicating the cleanup of hazardous waste sites.

"Is the current standard protective of human health? The answer is: Not really," said Robert Goyer, the panel chairman and a professor emeritus of pathology at the University of Western Ontario. "There is a high risk of some cancers, especially bladder cancer."

Arsenic occurs naturally in some soils but is also a byproduct of certain types of industrial mining and chemical production. Acutely toxic at high levels, arsenic has been shown in recent years to be a potent carcinogen, based on studies of Asian and Latin American villages with large amounts of the contaminant in water supplies.

Arsenic levels in the United States are generally much lower, but at least 32 million Americans in western states consume water that contains from 2 to 50 parts per billion, a 1995 EPA assessment shows. Arsenic levels are not a concern in Washington area water supplies.

The limit for drinking water – 50 parts per billion – was set in 1942, based on animal toxicity studies. In 1962, the EPA's predecessor, the Public Health Service, recommended a limit of 10 parts per billion for interstate water suppliers, the same standard that was later adopted by the World Health Organization. But the official U.S. policy remained unchanged for the next three decades while government scientists debated contradictory evidence over whether relatively small amounts of arsenic are harmful.

That debate appears to be ending, at least for now. While acknowledging that uncertainties remain about the risks from low-level exposure, the NAS panel concluded that the EPA's standard "does not sufficiently protect public health."

Extrapolating from recent epidemiological studies, some panel members estimated the risk of bladder cancer at one in 1,000 for people consuming arsenic at the maximum level allowed by the EPA. The overall cancer risk may be as high as one in 100, the report said. Goyer described the one-in-100 projection as "very controversial" among some members of the panel.

The EPA has not yet decided what the new arsenic limit may be, but sources familiar with the agency's deliberations have cited a range of two to 20 parts per billion. The new report did not recommend a specific new standard. But Charles Fox, the EPA's assistant administrator for water, said the NAS study gives agency a strong basis for action.

"The study suggests that additional protections are warranted, and that's consistent with how we're approaching the rulemaking process," Fox said.

But some EPA critics say the action comes far too late. Regulators missed a succession of deadlines since 1974 to review the health risk from arsenic, allowing an outdated standard to remain in place, said Erik Olson, senior attorney with the Natural Resources Defense Council.

"This sends up a big red flare," Olson said. "There's a major public health threat from arsenic in tap water, and this report confirms that."

The costs of strengthening the standard will largely fall on water suppliers and their customers, who will have pay for expensive treatment in areas where arsenic levels are high. The American Water Works Association, a trade group, estimates that a new standard of 10 parts per billion would cost utilities $1 billion a year. Still, the NAS panel's recommendations were well-grounded and should be followed, a spokesman said.

"Now that we have scientific consensus . . . we need to go forward in establishing an appropriate new regulation that protects the health of all Americans," said association Executive Director Jack Hoffbuhr.