On January 6, 2023, EPA released a proposal to revise the primary health-based National Ambient Air Quality Standard ("NAAQS") for fine particulate matter, known as PM 2.5, or more commonly, soot. Specifically, EPA's proposal would lower the current NAAQS from 12 micrograms per cubic meter to a new maximum level between 9 and 10 micrograms. Notably, the proposal would not change the daily exposure limit (i.e., the 24-hour fine particle standard), which was set at 35 micrograms per cubic meter in 2012. However, EPA is soliciting comments on whether the 24-hour standard should be lowered in the future to 25 micrograms per cubic meter. Nevertheless, a new NAAQS at any of the proposed levels would likely more than double the current number of PM 2.5 non-attainment areas, where new and modified major sources of air emissions need to install controls that meet the lowest achievable emissions rate and provide offsets.
EPA's proposal also seeks to revise other aspects of the PM standards, such as monitoring requirements and the Air Quality Index, or AQI. The proposal notes that these revisions are necessary in order to enhance air quality protection and ensure compliance among states and tribal nations with the proposed NAAQS for PM 2.5.
Comments on the proposed rule are due 60 days from publication in the Federal Register. Industry participants affected by the proposed rule should consider participating in the public comment period. EPA and state air quality regulators may use this as an opportunity to promulgate future rules that target emissions from sources, such as refineries and power plants.
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