On January 6, 2023, EPA released a pre-publication version of its highly anticipated proposal to strengthen the National Ambient Air Quality Standard (“NAAQS”) for fine particulate matter or PM2.5, one of two classes of particulate matter designated as “criteria pollutants” under the Clean Air Act (“CAA”). EPA’s proposal to lower the “primary”1 annual standard for PM2.5 from 12 µg/m3 to a level between 9 and 10 µg/m3 would have substantial impacts on large swaths of the western US. For example, if the standard is set at 9 µg/m3, populated areas of Utah, Colorado, Idaho, Montana, Nevada, and New Mexico would be designated as nonattainment and subject to stringent regulatory requirements.
EPA’s proposed range is consistent with recommendations provided to EPA by the Clean Air Scientific Advisory Committee (“CASAC”), an independent board of scientists that advises EPA. EPA is soliciting comment on revising the standard to as low as 8 µg/m3 and as high as 11 µg/m3.
EPA also proposes to retain the primary 24-hour standards for PM2.5 and PM10, as well as the “secondary” standards designed to protect environmental interests for both classes of PM. Despite pressure from environmental groups and a recommendation by the majority of the CASAC to reduce the 24-hour standard for PM2.5, EPA proposes to conclude that the current data does not call into question the adequacy of the 24-hour standards. Nonetheless, EPA also proposes to solicit comment on whether revising the primary 24-hour standard for PM2.5 to as low as 25 µg/m3 is warranted.
EPA has not lowered the annual standard since 2012. If finalized, a lowered annual PM2.5 standard would have significant regulatory and permitting implications. States that fail to meet the standard must submit to EPA new State Implementation Plans with an updated permitting framework and sufficient controls to reach attainment. Permitting of new and expanded facilities in nonattainment issues is substantially more costly as stringent controls and offsets are required.
Finally, the rule proposes to improve PM data monitoring in communities that are at increased risk of PM2.5 exposure and health effects by adding an environmental justice factor to the monitoring network design criteria. This new factor will account for the proximity of such at-risk populations to sources of PM pollution.
While the CAA prohibits EPA from considering costs in setting or revising NAAQS, the proposed rule includes a Regulatory Impact Analysis (“RIA”) of the costs and benefits of implementing the standards as required by Executive Orders 12866 and 13563. In the RIA, EPA concludes that an annual standard of 10 µg/m3 for PM2.5 could result in public health benefits valued at $17 billion in 2032 while a standard of 9 µg/m3 could result in benefits up to $43 billion.
EPA will accept public comment for 60 days after publication in the Federal Register and anticipates finalization of the rule by the end of 2023.
1 “Primary” standards are set to protect public health while “secondary” standards concern public welfare.