EPA Proposes to Redesignate Allegheny County to Attainment of the 2012 NAAQS for PM2.5

The EPA on Nov. 20 published a proposed rule that would redesignate Allegheny County from “nonattainment” of the 2012 National Ambient Air Quality Standard for fine particulate matter (the “2012 NAAQS for PM2.5”) to “attainment.”  

EPA’s proposed rule is based on monitored air quality data that shows that all areas of the county attained the 2012 NAAQS for PM2.5 during the years 2018, 2019, and 2020.  The proposed rule also discusses more recent monitored air quality data, which shows that all areas of the county have continued to attain the 2012 NAAQS for PM2.5 since 2020.

To attain the 2012 NAAQS for PM2.5, the three-year average of the annual arithmetic mean of monitored air quality data for an area must not exceed 12 micrograms per cubic meter (12 µg/m³).  

Among other requirements, to be redesignated from “nonattainment” to “attainment” of a NAAQS the air quality regulator for an area must submit a plan to EPA that shows that the area will continue to attain the NAAQS (which the Allegheny County Health Department has done).

EPA’s proposed rule also identifies some of the emission controls that local sources used to reduce their emissions of PM2.5 since the promulgation of the 2012 NAAQS for PM2.5, facility closures that contributed to reductions in PM2.5 levels in Allegheny County, and federal and state regulations that contributed to those same reductions.  

That part of the proposed rule is well worth a read. 

“The proposed rule is the capstone of a lot of good work that has been done over the last decade to bring Allegheny County into line with the 2012 NAAQS for PM2.5,” said GASP’s Senior Attorney John Baillie.

EPA is accepting comments on the proposed rule through December 22, 2025.  You can submit comments at www.regulations.gov or via email to gordon.mike@epa.gov; identify your comments by Docket ID No. EPA-R03-OAR-2025-1777.