October 4, 2004—Total emissions of the six principal pollutants identified in the Clean Air Act dropped again in 2003, signaling that America’s air is the cleanest in three decades, the US Environmental Protection Agency (EPA) reported on September 22. Annual emissions statistics for the six pollutants are considered major indicators of the quality of the nation’s air because of their importance for human health and the existence of their long-standing national standards. EPA reports that emissions have continued to decrease even as the US economy has increased more than 150 percent. A major reason for the nation’s progress is the market-based acid rain cap-and-trade program enacted in 1990. EPA expects the Clean Air Interstate Rule to continue this progress.
