Abstract

Summary of Argument: Throughout this proceeding, EPA has identified no policy or normative criteria to justify its NAAQS standards, thus suggesting that science alone can be used to determine the appropriate air quality standard. Science plays a critical, indeed essential, role in evaluating the risks of possible air quality standards being considered for adoption by EPA. However, science by itself cannot provide the justification for selecting a particular air quality standard. Especially in setting standards for non-threshold pollutants, such as in this case, scientific evidence cannot alone indicate where the standard should be set, since any level above zero will cause some health effects. To provide a principled and consistent basis for justifying the setting of such standards at some level above zero, EPA must articulate other factors -- whether they be costs or other policy criteria -- to guide its decisions on where to set national ambient air quality standards.