The Clean Air Act (CAA) was founded on the principle that a maximum safe national ambient air quality standard (NAAQS) concentration existed for each pollutant. Once those concentrations were defined, emission limitations for individual plants could be determined that ensured those concentrations would not be exceeded in ambient air. The CAA gives the states the primary authority to define the emission limitations necessary to meet the NAAQS in their airsheds. The collection of emission limits forms the state implementation plan (SIP) that, when approved by the U.S.

Whether U.S. EPA and states can regulate emissions outside the facility fence line is a critical factor in shaping the regulatory response to climate change using Clean Air Act §111. There has been much rhetoric about the ability of states and EPA to create regulatory tools such as emissions trading of greenhouse gases, but policy experts and professionals need a more definitive answer. To address this topic, ELI held the second seminar of its Professional Practice Series.