AbstractTen years ago, environmental problems were easy to define: The Hudson and Potomac were polluted; Los Angeles had lousy air; some waste dumps were highly toxic. Solutions were also relatively straightforward: the Clean Air Act for dirty airsheds; the Clean Water Act for dirty rivers; the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, better known as Superfund) for hazardous waste sites. Unfortunately, reality is not quite so neat. We now know that we were seeing—and treating—symptoms, not the disease its