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1.1 BACKGROUND

Air quality conditions in the Houston area are not in compliance with the National Ambient Air Quality Standards (NAAQS). The area is known to exceed the 1-hr and 8-hr ozone standards, and new monitoring information indicates the area is likely to exceed the new annual NAAQS for fine particulate matter (PM2. 5). Extensive analysis of the ozone problem, including detailed photochemical modeling for the State Implementation Plan (SIP), indicates large emission reductions are needed to achieve compliance with the 1-hr ozone standard. Attainment of the new 8-hr ozone standard will probably be more difficult than attainment of the older 1-hr standard. Characterization of the PM2. 5 problem is in its early stages and much work is needed to understand the source contributions and options for mitigation of the problem. There is a clear need to characterize the relationship between ozone and PM2. 5 in the Houston area and understand the likely effects of changes in common precursor emissions on these species. In addition, there is concern for human exposure to other hazardous air pollutants (HAPs) that are not covered by NAAQS. The sources that contribute to ozone formation and ambient PM2. 5 may also contribute to the ambient concentrations of toxic compounds.

The understanding of emissions and atmospheric processes has progressed to a state where integrated multi-species approaches are needed for development of control strategies. While many compounds are emitted into ambient air and many connections exist between species via complex reactions that may produce additional species, there is still only “one …