Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen, Oxides of Sulfur, and Particulate Matter (Final)
Jan. 2, 2025
Based on the EPA's review of the air quality criteria for ecological effects and secondary national ambient air quality standards (NAAQS) for oxides of nitrogen (N oxides), oxides of sulfur (SOX), and particulate matter (PM), the EPA is revising the existing secondary sulfur dioxide (SO2) standard to an annual average, averaged over three consecutive years, with a level of 10 parts per billion (ppb). Additionally, the Agency is retaining the existing secondary standards for N oxides and PM, without revision. The EPA is also finalizing revisions to the data handling requirements for the secondary SO2 NAAQS. This final rule is effective on 27 January 2025. POC is Ms. Ginger Tennant, EPA, Health and Environmental Impacts Division, Office of Air Quality Planning and Standards (mail code C539-04), Research Triangle Park, NC 27711; tele: (919) 541-4072; email: tennant.ginger@epa.gov. (Federal Register 27 December 2024 [Rule] Pages 105692-105788)