by Amanda Reeve

The U.S. Environmental Protection Agency (USEPA) announced on January 6, 2023, that it is proposing to modify the National Ambient Air Quality Standard (NAAQS) for Fine Particulate Matter (PM2.5).  The current annual primary (health-based) NAAQS for PM2.5 is set at 12.0 micrograms per cubic meter of air (µg/m3); but it could soon be as stringent as 9.0 µg/m3.

While the USEPA is proposing to make the primary (health-based) annual standard more stringent for PM2.5, it is preparing to retain the current secondary (welfare-based) annual PM2.5 standard of 15.0 µg/m3, the primary and secondary 24-hour PM2.5 standard of 35 µg/m3; and the primary and secondary 24-hour standard of 150 µg/m3 for Coarse Particulate Matter (PM10). 

Based on current air monitoring data, the USEPA illustrates that potentially 50 counties will not meet a new proposed annual primary PM2.5 standard of 10.0 µg/m3; and an additional 62 counties will not be able to meet a proposed annual primary PM2.5 standard of 9.0 µg/m3.

The USEPA submitted the Proposed Rule on January 5, 2023, to the Federal Register for publication. The public will have an opportunity to submit comments regarding this proposal for 60 days after the date of publication in the Federal Register.