In an action intended to correct an inadvertent requirement included in the 2008 particulate matter (PM)-2.5 new source review (NSR) implementation rule, the EPA has issued an amendment to revise the definition of regulated NSR pollutant by clarifying when condensable PM should be measured. 

Condensable PM is not directly emitted as a solid or liquid at the stack.  Instead, following discharge from the stack, gaseous emissions, such as sulfuric acid mist, ammonium sulfate, and certain metal vapors, condense upon cooling and dilution in the ambient air to form solid or liquid particles.   

Under the 2008 definition, state and local agencies and the regulated community were required to include the condensable PM fraction in all measurements of particulate matter emissions, PM-10 emissions, and PM-2.5 emissions. 

Particulate matter emissions

The latest action specifically addresses the condensable PM fraction in particulate matter emissions, a term that includes particles that are significantly larger than either PM-2.5 or PM-10 and are used primarily to measure compliance with EPA’s existing New Source Performance Standards (NSPS) for PM.  The EPA states that the amount of particulate matter emissions that a source has the potential to emit is not intended to be used for determining whether an area can attain or maintain either of the existing sets of National Ambient Air Quality Standards (NAAQS) for particle pollution (i.e., PM-2.5 and PM-10).  The Agency elaborates:

“PM-10 emissions and PM-2.5 emissions are regulated as criteria pollutants (that is, under the portion of the definition of regulated NSR pollutant that refers to ‘[a]ny pollutant for which a national ambient air quality standard has been promulgated…’), and are required to include the condensable PM fraction emitted by a source.

“By contrast, particulate matter emissions are regulated as a non-criteria pollutant under the portion of the definition that refers to ‘[a]ny pollutant that is subject to any standard promulgated under section 111 of the Act,’ where the condensable PM fraction generally is not required to be included in measurements to determine compliance with standards of performance for PM.”

Accordingly, the new rule removes the general requirement in the definition of regulated NSR pollutant to include condensable PM when measuring particulate matter emissions in the context of the Prevention of Significant Deterioration (PSD) and NSR regulations.

Other regulations

The EPA states that the rule preserves the requirement in some cases to count the condensable PM fraction with regard to PM emissions.  The first case is for a source that is subject to an NSPS for which the condensable PM fraction must be included in the determination of compliance with the standard of performance for PM.  The second case is where the applicable state implementation plan already requires that the condensable PM fraction be included in the measurement of PM emissions.   The third case is where a source that emits PM emissions is not subject to an NSPS, but is required by the reviewing authority to include the condensable PM fraction.

Click here to read EPA’s final rule amending the definition of regulated NSR pollutant with regard to condensable particulate matter.