EPA finds no change necessary in nitrogen 
oxides (NOx) minimization program

WASHINGTON (10/12/05) -- Following an evaluation of the current program to minimize the impact of nitrogen oxides (NOx) emissions and prevent significant declines in air quality, EPA has found that the program is working and that no change is necessary.

The program, known as Prevention of Significant Deterioration (PSD), addresses the need to allow growth while maintaining air quality in areas that are already clean. Presently, the national ambient air quality standards for nitrogen dioxide (NO2) are being attained throughout the U.S.

"Significant deterioration" is defined as the maximum allowable pollutant concentration increase - also known as an "increment" - above an existing baseline concentration for an area. An increment is established for areas (e.g., counties) that states designate as attaining national air quality standards. Emissions increases that cause the increment to be exceeded for a given pollutant are not permitted. 

While the final rule does not modify the existing increment system for NO2, it does recognize that states may continue to choose an alternative approach. The state must demonstrate that an alternative program satisfies Clean Air Act requirements and prevents significant deterioration from emissions of nitrogen oxides (NOx).

In February 2005, EPA proposed to allow states that choose to implement a federally administered cap and trade program for sources of NOx - such as the Clean Air Interstate Rule - to rely on those emissions reductions to prevent significant deterioration of NOx air quality. EPA is not taking final action on that proposal in this rule. 

The final rule is available online.