The program helped improve air quality in 95 percent of nonattainment areas in the east, with 64 percent of these areas now below the ozone standard. Some of the report highlights show that:
- the largest NOx emission reductions occurred in Ohio, Indiana, Illinois, West Virginia, and Kentucky; and
- the reduction of NOx – a precursor to ground-level ozone, or smog – has helped reduce ozone concentrations an average of 10 percent in the eastern part of the country since the start of the program in 2003.
The program is a market-based cap and trade partnership between federal and state governments to reduce the regional transport of NOx during the ozone season. The program provides facilities flexibility to choose their control options including installing control technologies, optimizing existing controls, and switching fuels. Stringent monitoring, reporting and automatic penalties have led to a compliance rate of over 99 percent.
EPA, state and local programs have contributed to the decrease in NOx and ozone levels since 1990. The program has contributed the most to improvements in ozone levels since 2003.