This month and next, EM focuses its attention on two major Clean Air Act (CAA) rules recently promulgated by the U.S. Environmental Protection Agency (EPA): the Clean Air Interstate Rule (CAIR) and the Clean Air Mercury Rule (CAMR). In this month’s issue, EM presents two articles summarizing the main features of CAIR and CAMR. Next month’s issue will follow these up by offering perspectives on the two rules from representatives of a number of stakeholders, including EPA, the states, the regulated community, and the environmental community.
In 1997, EPA revised the National Ambient Air Quality Standards (NAAQS) for fine particulate matter (PM2.5) and ozone; however, the standards were legally challenged all the way to the U.S. Supreme Court. Much of the urbanized eastern United States remains in “nonattainment” of the revised NAAQS (see Figure 1). Subsequently, EPA recognized that emissions control strategies by individual states (with nonattainment areas) alone were not adequate to attain the standards because pollutants transported from upwind areas contributed significantly to the exceedance of the NAAQS.