More research is necessary for emissions characterization and air quality model testing and development to meet implementation deadlines (see Chapter 5). Measurements of source emission rates for PM and precursor gases as well as evaluation of models are needed, because states are in the process of developing state implementation plans for attaining PM NAAQS. To expedite progress on those topics, EPA should provide more guidance, leadership, and coordination among the groups carrying out this work, particularly those conducting emissions characterization (see Chapter 6).
Results of epidemiological research could provide greater information about those components of PM and air pollution that can most impact health. Future state implementation plans (SIPs), which are plans for reducing emissions so that an area can come into compliance with NAAQS, could therefore benefit from new and existing research in this area. Such information would enable SIPs to prioritize emission-control efforts starting with those sources contributing the greatest potential health impacts.