On March 10, 2006, the EPA issued a final rule on fine particulate matter (PM2.5) and coarse particulate matter (PM10) hot-spot analyses. The rule lays out project-level transportation conformity determinations for the new PM2.5 and existing PM10 National Ambient Air Quality Standards (NAAQS).

The new rule establishes criteria for determining which transportation projects must be analyzed for local particle emission impacts in PM2.5 and PM10 nonattainment and maintenance areas. It also establishes requirements in PM2.5 areas and revises existing requirements in PM10 areas, and requires quantitative PM2.5 hot-spot analyses only for projects of “air quality concern” in nonattainment and maintenance areas at all times - both before and after a PM2.5 state implementation plan is submitted.

The agency had not yet released its future modeling guidance as of this publication, but state and local agencies could consider conducting qualitative hot-spot analyses for these projects regardless. Also, the final rule allows the DOT, in consultation with the EPA, to make categorical hot-spot findings that would further streamline quantitative hot-spot analysis requirements as appropriate in PM2.5 areas, as the existing conformity rule already allows in PM10 areas for some projects. This final rule requires a qualitative PM2.5 hot-spot analysis be completed for project-level conformity determinations for projects of air quality concern completed in PM2.5 nonattainment areas on or after April 5, 2006, when the conformity requirements apply. In the future, the EPA will address how PM2.5 hot-spot analyses should consider both applicable standards and quantitative hot-spot modeling guidance.