Why will NOx sources in attainment areas have to put controls in place?
The best available science shows that controlling ozone requires a combination of local control of volatile organic compounds (VOCs) and regional reductions of nitrogen oxides (NOx). Historically, state and local ozone smog control strategies have focused on reducing VOCs in local areas. However, NOx emissions–from sources like power plants sometimes located in attainment areas hundreds of miles away–can contribute to pollution problems in downwind areas. Some of these sources of NOx are very large and to date have been virtually uncontrolled. It is unfair to require downwind areas to continually reduce local emissions (often at very high cost) when the same benefits can be achieved, more cost effectively from upwind sources like power plants. There are ancillary benefits, as well. Local reductions help to mitigate the harmful effects of nitrogen oxides on sensitive waterways and estuaries like the Chesapeake Bay.
