On January 6, 2023, EPA published a proposed rule for particulate matter National Ambient Air Quality Standard (NAAQS) that would retain the primary 24-hr PM2.5 standard (35 µg/m3) and reduce the annual standard from 12 µg/m3 to 9 µg/m3. The agency is also taking comments on reducing the 24-hr PM2.5 standard as low as 25 µg/m3 and the annual standard as low as 8 µg/m3. The Clean Air Act requires that EPA review the NAAQS every five years to ensure their adequacy. The last review of the PM NAAQS was completed in December 2020 with no change, but EPA announced their decision to reconsider this action in June 2021. Although no changes to the PM10 NAAQS standard are expected at this time, changes to the PM2.5 NAAQS standard are proposed.
This proposal takes into account thousands of scientific studies since the last update of PM NAAQS in 2012 that have demonstrated the dangers of long term soot exposure. The evidence supports a likely relationship between long-term PM2.5 exposure and respiratory effects, nervous system effects, and cancer. EPA estimates that if finalized, a strengthened annual PM2.5 standard of 9 µg/m3 would:
- Prevent up to 4,2000 premature deaths per year;
- Prevent 270,000 lost workdays per year; and
- Result in as much as $43 billion in net health benefits in 2032.
EPA accepted public comments on the proposed rule through March 7th and has already held public hearings. Additional information will be made available on the National Ambient Air Quality Standards (NAAQS) for PM webpage.
State, local, and tribal air agencies will be required to use this standard after it is finalized federally. Once in effect, this will cause more difficulty when emission units require PM2.5 modeling as part of a permit application or modification. Several areas throughout the Pacific Northwest have high particulate background concentrations, which will narrow the allowable “new” particulate emitted even further. If you are planning any facility expansions or new sources that include particulate matter emissions and want to know if this rule would effect your business, please contact Spring Environmental for more information.