In March 2025, Administrator Zeldin announced that EPA will reconsider a number of regulations in order to advance various executive orders issued by President Trump and fulfill EPA’s own Powering the Great American Comeback Initiative. These efforts include the 2024 ambient air standard for particulate matter, the 2009 endangerment finding, and the scope of jurisdiction over ‘adjacent wetlands after the Supreme Court’s 2023 decision in Sackett.

In the Biden Administration, EPA lowered the National Ambient Air Quality Standard for particulate matter, the PM 2.5 NAAQS. The standard was reduced to levels that were close to background levels in some areas. EPA announced it is “revisiting” the lower standard because, among other things, the lower standard “raised serious concerns from states across the country and served as a major obstacle to permitting.”

So far, though, EPA has not issued a proposal to revisit the PM 2.5 NAAQS. It faces some hurdles in doing so. It must be done through the administrative rule-making process, which includes public notice and comment. Further, to survive judicial review, EPA must provide a reasoned explanation for the basis of the revision. EPA also stated it would “soon release guidance to increase flexibility on NAAQS implementation…and direction on permitting obligations.” However, these items have not yet been issued.

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