Based on the Environmental Protection Agency's (EPA's) reconsideration of the air quality criteria and the national ambient air quality standards (NAAQS) for particulate matter (PM), the EPA is revising the primary annual PM2.5 standard by lowering the level from 12.0 µg/m3 to 9.0 µg/m3. The Agency is retaining the current primary 24-hour PM2.5 standard and the primary 24-hour PM10 standard. The Agency also is not changing the secondary 24-hour PM2.5 standard, secondary annual PM2.5 standard, and secondary 24-hour PM10 standard at this time. The EPA is also finalizing revisions to other key aspects related to the PM NAAQS, including revisions to the Air Quality Index (AQI) and monitoring requirements for the PM NAAQS. This final rule is effective 6 May 2024. POC is Dr. Lars Perlmutt, Health and Environmental Impacts Division, Office of Air Quality Planning and Standards, U.S. EPA, Mail Code C539–04, Research Triangle Park, NC 27711; tele: (919) 541–3037; email: perlmutt.lars@epa.gov.

(Federal Register 6 March 2024 [Rule] Pages 16202-16406)