Corridor that are subject to NSR. Any resulting emission increases are not guaranteed to be offset by other programs such as CAIR. On the other hand, the CAIR program, by encouraging reductions in SO2 and NOx emissions, might lead to the retrofitting of controls that would also reduce CO, PM, and VOC emissions.


The regulatory background has continued to evolve during the period of our study. New settlements have been reached, new regulatory initiatives have been unveiled, and court decisions that affect the NSR programs have been handed down. We have tried to take into account all those changes in our report. However, we caution the reader that matters have not yet come to rest and that NSR will probably be affected by future and unpredictable events.

Three matters are particularly significant:

  • The 2002 rules are partly in effect in a few states; the remaining portions were struck down. The 2003 rules never went into effect and have been invalidated.

  • It is unclear at this writing how much emission reduction will be brought about by the enforcement initiative. That is partly because the courts have split over whether the enforcement initiative is in accord with the CAA. This makes it difficult to analyze the effects of changes to the NSR programs.

  • As we have stressed, the CAIR rule (whose fate in the courts is undetermined) may have a substantial effect on the consequences of the NSR reforms.

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