Fine Particulates (PM2.5) are perhaps the most important conventional pollutant from a health perspective. Permit Applicants must demonstrate new emissions will not exceed the NAAQS by modeling the impact of additional emissions from new or upgraded facilities.

Existing background levels of PM2.5 are very close to the NAAQS in many parts of the country.  Considering this lack of headroom and the fact that EPA’s workhorse model cannot adequately handle the chemistry associated with PM2.5, permitting new sources can be a significant challenge. This program will discuss the evolution of PM2.5 modeling, the limits of existing tools, current issues in modeling, anticipated changes, and will provide guidance for Permittees and Permit writers who must address these issues.