Implementation of the New Source Review (NSR) Program for Particulate Matter Less Than 2.5 Micrometers (PM2.5): Amendment to the Definition of “Regulated NSR Pollutant” Concerning Condensable Particulate Matter

The EPA is issuing a final rule that revises the definition of "regulated NSR pollutant" contained in two sets of Prevention of Significant Deterioration (PSD) regulations and in the EPA's Emission Offset Interpretative Ruling. The revision corrects an inadvertent error made in 2008 when the EPA issued its rule to implement the New Source Review (NSR) program for fine particles with an aerodynamic diameter of less than or equal to 2.5 micrometers (PM<INF>2.5</INF>). This revision removes a general requirement in the definition of "regulated NSR pollutant" to include condensable PM when measuring one of the emissions-related indicators for particulate matter (PM) known as "particulate matter emissions" in the context of the PSD and NSR regulations. However, the rule preserves the requirement in some particular cases to include condensable PM in measurements of "particulate matter emissions" as required by other regulations. In addition, measurement of condensable PM continues to be required in all cases for two other emissions-related indicators for emissions of PM-- emissions of particles with an aerodynamic diameter of less than or equal to 10 micrometers (PM<INF>10</INF> emissions) and PM<INF>2.5</INF> emissions.