The Clean Air Act requires EPA to review new science on the public health and environmental impacts of air pollutants every 5 years and revise the National Ambient Air Quality Standards (NAAQS), as necessary. EPA lowered the annual NAAQS for PM2.5 from 12.0 to 9.0 micrograms per cubic meter (µg/m3) on February 7, 2024. Learn a whole lot more about this topic in the National Tribal Air Association’s November newsletter. See pages 2-3.