EPA developed CAIR to reduce emissions of sulfur and nitrogen oxides (SOx and NOx) from the power sector to help 28 eastern states and the District of Columbia meet NAAQS for O3 and fine particles (PM2.5) and to reduce regional haze. EPA also viewed CAIR as a key driver for mercury emissions reductions. The rule specifically targeted emissions that resulted in long-range transport that contributed significantly to nonattainment of the NAAQS in downwind states. EPA developed CAIR after concluding the U.S. Congress was unlikely to pass the Clear Skies Act, the Bush Administration’s first choice for addressing multiple pollutants (SOx, NOx, and mercury) from the power sector. CAIR was recognized as EPA’s attempt to get similar results under the existing U.S. Clean Air Act (CAA). Like Clear Skies, CAIR was built on the widely praised market-based emissions cap-and-trade/banking programs established to reduce acid rain (Title IV of the CAA) and ground-level O3 (the NOx Budget Trading Program, sometimes called the NOx SIP Call, issued under Section 110(a)(2)(d) of the CAA). CAIR established regional sulfur dioxide (SO2) and NOx caps that would reduce emissions of SOx and NOx from power plants in the eastern United States, and the levels and timing of the caps were similar to those previously proposed in the legislation.