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.
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.