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The new rules, however, will not be issued in a vacuum. If they are adopted as written, hundreds of counties across the nation--some of which have worked hard to meet the old, looser standards--will suddenly be in violation. This infuriates businesspeople who would be forced to absorb the costs of any cleanup, and is why industry groups, including the National Association of Manufacturers and the American Petroleum Institute, carried out a major lobbying and advertising campaign to force Browner to retreat. Big-city mayors joined forces with the business lobby, fearing the new regulations would spur an exodus of factories from urban areas to places with lower pollution. They too put a lot of pressure on the White House.
Charges by Browner's opponents that bad science underlies the new rules can't be dismissed casually. Despite those scores of studies, there is still no smoking gun linking soot particles, in particular, to lung disease. Cities that have lots of soot in the air do tend to have more illness and deaths, but that merely shows an association; it doesn't prove cause and effect. Nobody knows, moreover, by exactly what mechanism particles might cause disease. Given the state of the science, any analysis of pollution risk must be a judgment call.
How good is the EPA's judgment? Industry groups are not the only ones saying it's questionable. The studies available today, says Robert Phalen, director of the Air Pollution Health Effects Laboratory at the University of California at Irvine and an occasional corporate consultant, are just setting the groundwork for future research on whether soot is harmful. "It could be a tragic mistake," says Phalen, "to jump toward a regulation before you know what is going on."
Indeed, some scientists argue that restrictions on soot could, paradoxically, cause more illness, not less. It may be the smallest of the small particles that cause the most damage, according to Gunter Oberdorster, a toxicologist at the University of Rochester. But these ultrafine particles tend to be vacuumed up by their larger cousins. Filter out the latter--which is easier to do--and the former would be free to wreak even greater havoc.
Browner and her scientific advisers are aware of the uncertainties, and don't pretend that their regulations are based on conclusive proof. "There are gaps in the science," acknowledges Dr. Jonathan Samet, chairman of epidemiology at the Johns Hopkins school of public health. "But the science provides a warning." In any case, argues Browner, the law demands that the EPA set standards that provide an "adequate margin of safety." If public-health officials had waited to uncover precisely how lead and tobacco smoke cause illness, thousands of people would have died unnecessarily.