Reconsideration of the National Ambient Air Quality Standards for Particulate Matter

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 PM<INF>2.5</INF> standard by lowering the level from 12.0 [micro]g/m\3\ to 9.0 [micro]g/m\3\. The Agency is retaining the current primary 24-hour PM<INF>2.5</INF> standard and the primary 24-hour PM<INF>10</INF> standard. The Agency also is not changing the secondary 24-hour PM<INF>2.5</INF> standard, secondary annual PM<INF>2.5</INF> standard, and secondary 24-hour PM<INF>10</INF> 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.