EPA issued a final rule lowering the national ambient air quality standards (NAAQS) for soot (particulate matter or PM). The rule reduced the primary annual PM2.5 standard from 12.0 µg/m3 to 9.0 µg/m3. EPA also adjusted the Air Quality Index (the metric used for advising the public on real-time air quality in their area) to reflect new information on the health effects of PM2.5, including emissions from wildfires. The revised PM2.5 NAAQS included recommendations for how to address environmental justice concerns for at-risk groups in State Implementation Plans. The final rule went into effect on May 6, 2024.