• The SIP process has resulted in a general decrease in criteria pollutant concentrations in the United States and, in some areas, has resulted in NAAQS attainment.

  • The sequencing of attainment dates for O3, based on nonattainment classification, provides a more reasonable and flexible timetable for state and local agencies to come to address this persistent air pollution problem.

Limitations of the SIP Process11

  • Implementation of federal, regional, and local control measures through the SIP process has not resulted in attainment for O3 and PM in many areas in the United States.

  • The SIP process has become overly bureaucratic and draws attention and resources away from the more germane issues of tracking progress and assessing performance.

  • The attainment-demonstration SIP places too much emphasis on uncertain emissions-based modeling simulations of future air pollution episodes.

  • SIPs must be developed individually for each criteria pollutant, making it difficult for states and local agencies to consider potentially more cost-effective and more protective multipollutant strategies.

  • The SIP process lacks sufficient mechanisms and governmental infrastructure for addressing multistate airshed aspects of air pollution.


Recommendations are provided in Chapter 7.

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