On January 15, 2013, the Environmental Protection Agency (EPA) published a final rule revising the National Ambient Air Quality Standard (NAAQS) for particulate matter (PM). The revised air quality standards were completed pursuant to the Clean Air Act (CAA) and, in part, in response to a court order and consent agreement. Based on its review of scientific studies available since the agency's previous review in 2006, EPA determined that evidence continued...