www.sciam.com SCIENTIFIC AMERICAN 21 news SCAN generally more concentrated in groundwater than in lakes or streams.) In villages with the most severely contaminated wells, the death rates from bladder cancer were dozens of times above normal. Similar studies in Ar- gentina and Chile later corroborated those findings. In a region of northern Chile, for ex- ample, researchers determined that 7 percent of all deaths among people over the age of 30 could be attributed to arsenic. In the Taiwan study, the lowest median level of arsenic was 170 micrograms per liter. To determine the risk at the 50- and 10-mi- crogram levels, epidemiologists extrapolated the health effects in a linear way (that is, half the exposure leads to half the cancer risk). Some toxicologists have criticized this ap- proach, saying that arsenic concentrations may have to exceed a threshold level to cause cancer. But new research suggests that if this threshold exists, it is most likely well below 10 micrograms per liter. In the U.S., most public water systems with high arsenic concentrations are in the western states [see table at right]. The EPA originally proposed lowering the arsenic stan- dard to five micrograms per liter, but the agency doubled the allowable level after rep- resentatives of the water systems complained about the expense of removing the carcino- gen. In the regulation issued in January, the agency estimated that 4,100 systems serving some 13 million people would have to pay a total of $180 million annually to implement the 10-microgram standard. The EPA claimed that the rule would prevent 21 to 30 deaths from lung and bladder cancer each year, but some epidemiologists say the standard could save 10 times as many lives. So what prompted the EPA to suddenly call for a reassessment of the standard? Some environmentalists speculate that industry groups such as the National Mining Associ- ation, which filed a court petition in March to overturn the arsenic rule, put pressure on the Bush administration. The tailings from mines are often laced with arsenic. Because the EPA’s cleanup regulations are based on drinking-water standards, tightening the re- strictions on arsenic could vastly increase the cost of decontaminating abandoned mines, many of which are Superfund sites. Whitman has asked the NAS to review the EPA’s risk analysis of arsenic. Many research- ers fear that she will use the new report to jus- tify a limit of 20 micrograms per liter, a stan- dard that would cost about $110 million less than the stricter regulation but save only half as many lives. “The weaker standard would not be sufficient to protect public health,” says Chuck Fox, who headed the EPA’s Office of Water until the change of administrations. “The standard for arsenic should be as close to zero as feasible.” F or years, archaeologists have been speaking the language of astronomers. Remote-sensing techniques have found lost cities; celestial alignments have shed light on temples and pyramids. But lately the flow of ideas has reversed. Astronomers have re- alized that our galaxy is an intricately layered place—a Tel Galaxia that encodes a rich his- tory like buried strata of an ancient city. Ce- lestial excavations are starting to provide a much needed reality check on theories not just of the galaxy but also of the broader cos- mos. “It’s not all that easy to find experi- mental verification of these theories,” says Heather L. Morrison of Case Western Re- serve University. “Studies of the Milky Way Galactic Archaeology DIGGING INTO THE MILKY WAY’S PAST EXPOSES ITS LIFE AS A CANNIBAL BY GEORGE MUSSER ASTRONOMY Large municipal water systems with average arsenic levels above the proposed 10-microgram standard: CITY ARSENIC LEVEL (micrograms per liter) Norman, Okla. 36.3 Chino Hills, Calif. 30.2 Lakewood, Calif. 15.1 Lancaster, Calif. 14.5 Albuquerque, N.M. 14.2 Moore, Okla. 12.6 Rio Rancho, N.M. 12.4 Victoria, Tex. 11.6 Midland, Tex. 11.1 Scottsdale, Ariz. 11.1 SOURCE: Natural Resources Defense Council NEED TO KNOW: DANGER ZONES ABANDONED MINE in Butte, Mont., is laced with arsenic. WALTER HINICK Montana Standard/AP Photo Copyright 2001 Scientific American, Inc.