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EPA Moves Forward with PM2.5 and Ozone NAAQS

Although a bit outside our normal NSR-centered view, we thought that we would highlight recent developments with the PM2.5 and Ozone NAAQS that may affect NSR practitioners moving forward.


On October 29, 2021, the EPA filed a notice in State of New York v. EPA, No. 21-1028 (D.C. Cir.), a petition for review brought by several states challenging the Trump EPA's decision not to revise the ozone NAAQS, stating that "Respondents United States Environmental Protection Agency, et al. ("EPA") have now determined that EPA will be reconsidering the 2020 Ozone NAAQS Decision, with the intention of completing the reconsideration by the end of 2023. In an accompanying declaration from Joseph Goffman, Principal Deputy Assistant Administrator, the EPA stated that "EPA anticipates that it will update one or more documents and convene an ozone review panel for this reconsideration, as the review of the Ozone NAAQS culminating in the 2020 Ozone NAAQS decision was completed without the benefit of an ozone-specific panel supporting the CASAC, as had been done in prior review." Based upon this process, EPA is petitioning the D.C. Circuit to hold the case challenging the 2020 Ozone NAAQS "in abeyance" until it completes the reconsideration process in December 2023.

Particulate NAAQS

In June 2021, the EPA announced that it would reconsider the December 2020 decision to retain the PM2.5 NAAQS. In September 2021, the EPA released a "Supplement to the 2019 Integrated Science Assessment for Particulate Matter (External Review Draft)" prepared by the Center for Public Health and Environmental Assessment. The Supplement looked at "new" data that is characterized as "of potentially greatest relevance" to the decision, including a U.S. and Canadian epidemiologic study, some "near ambient" studies, and studies showing "disparate impact" of particulate matter on non-White populations. Critically, the Supplement states that the recent U.S. and Canadian studies "report positive associations at lower PM2.5 concentrations (i.e., annual PM2.5 concentrations ranging from 5.9 to 16.5 ug/m3, mean 24-hour avg. PM2.5 concentrations ranging from 7.1 to 15.4 ug/m3)." This range may form the basis for subsequent recommendations by CASAC and EPA staff to the Administrator. The range is considerably lower than the current PM2.5 NAAQS, which has an annual value of 12 ug/m3 and the 24-hour average of 35 ug/m3. In subsequent statements, the EPA has indicated that it intends to release a proposed PM2.5 NAAQS in the summer of 2022 and to promulgate a new PM2.5 NAAQS, if appropriate, by first quarter 2023.


Based upon these statements and court filings by the EPA, it looks like late 2022 will be a busy time for reviewing and commenting on the proposed NAAQS and, to a lesser extent, implementation concerns. In addition, source contemplating PSD applications should remember that under the D.C. Circuit decision in Murray Energy that a new NAAQS is effective for PSD purposes immediately and that this precludes "grandfathering" of pending PSD applications at the time a new NAAQS is promulgated.


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