Published by the American Geological Institute
of the Earth Sciences
A naturally occurring intravenous drip of arsenic into the nation’s drinking water is receiving a serious dilution. On May 24, the Environmental Protection Agency (EPA) proposed slashing by 90 percent its standard for the maximum level of arsenic in drinking water.
Under the 1996 amendments to the Safe Drinking Water Act, Congress required that the agency propose a new standard by January 2000 and finalize the rule by Jan. 1, 2001. The EPA is now asking the public to submit comments on the costs vs. the benefits of alternative standards.
Last year the National Research Council urged the EPA to develop strict regulations for arsenic based on studies linking bladder and lung cancer, often fatal diseases, to the list of less serious maladies that may occur over a lifetime of drinking water having the current allowable levels of arsenic.
The change also follows a series of studies by government agencies showing areas in the West, Midwest and Northeast have water supplies with arsenic concentrations above the proposed limit. Although arsenic is often used by industries as a wood preservative, most arsenic contamination occurs naturally (see Arsenic travel tips).
“Arsenic is ubiquitous in the geologic record,” says research hydrologist Allen Welch of the U.S. Geological Survey in Carson City, Nev. On May 8, the USGS released a map indicating where arsenic in groundwater is found at concentrations that exceed the proposed limit. The survey’s results are similar to earlier surveys of arsenic in drinking water but are based on a much larger database.
The EPA standards set in 1975 were originally based on 1942 Public Health Service standards. The new proposal drops the allowable levels of arsenic from 50 micrograms per liter (or parts per billion) to 5 micrograms per liter. “The lifetime risk of health effects, such as bladder cancer, from drinking tap water with 5 parts per billion is one in 10,000,” says EPA statistician Andrew Schulman. That risk matches the agency’s traditional goal for minimizing risks of cancer to one in 10,000, but environmentalists argue the risk is still to high. Epidemiological data, however, are not available for evaluating risk at lower arsenic concentrations.
“The scientific evidence is challenging,” Schulman says. The EPA data extrapolated the cancer risk from studies on people in Taiwan who had consumed arsenic at 200 parts per billion, he says. “If you plot risk versus arsenic concentration in tap water and extrapolate down to zero on a straight line, the maximum risk at 5 parts per billion is one in 10,000.” No one is arguing that the risk at 5 parts per billion is any higher than that but if the model is based on a curve it may be even lower. Still, he adds, “there’s uncertainty.”
Two weeks before the EPA announced the proposal, the Natural Resources Defense Council had filed suit against the agency and the White House Office of Management and Budget. They were concerned the EPA had already missed three congressional deadlines and would be further delayed.
“The debate is really going to hit the streets now that they’ve released the proposal,” says Mike J. Facazio, lead researcher of the USGS arsenic study. The World Health Organization recommends a standard of 10 parts per billion, as do water utilities. But the Natural Resources Defense Council suggests a standard of 3 parts per billion. “Typical monitoring procedures can detect concentrations that low,” says Facazio, whose study detected 1 part per billion in groundwater. “And treatment technology can remove large amounts of arsenic to low levels, but it costs more.”
Indeed the EPA estimated that about 12 percent of the nation’s community water systems, serving some 22 million people, may have to pay the extra cost of about $400 million a year to dilute or remove arsenic down to 5 parts per billion. Water utilities argue the costs may reach $1.5 billion annually with cap costs or investment costs reaching $14 billion, says Doug Marsano, a spokesman for the American Water Works Association. “For people who wouldn’t meet the 5 parts per billion, no matter what you’re doing now, a new treatment facility system would be needed,” Marsano says. “Nobody disputes that the standard must come down, but it is incumbent upon EPA to take a closer look at the 10 parts per billion standard,” he says, adding that replacing treatment systems at that standard would be one-third the cost.
For more information
or call the EPA Safe Drinking Water Hotline at 1-800-426-4791.