40 CFR 50.1 - Definitions.

Based on its review of the air quality criteria and the national ambient air quality standards (NAAQS) for particulate matter (PM), the EPA is making revisions to the suite of standards for PM to provide requisite protection of public health and welfare and to make corresponding revisions to the data handling conventions for PM and to the ambient air monitoring, reporting, and network design requirements. The EPA also is making revisions to the prevention of significant deterioration (PSD) permitting program with respect to the NAAQS revisions. With regard to primary (health-based) standards for fine particles (generally referring to particles less than or equal to 2.5 micrometers (μm) in diameter, PM 2.5 ), the EPA is revising the annual PM 2.5 standard by lowering the level to 12.0 micrograms per cubic meter (μg/m 3 ) so as to provide increased protection against health effects associated with long- and short-term exposures (including premature mortality, increased hospital admissions and emergency department visits, and development of chronic respiratory disease), and to retain the 24-hour PM 2.5 standard at a level of 35 μg/m 3 . The EPA is revising the Air Quality Index (AQI) for PM 2.5 to be consistent with the revised primary PM 2.5 standards. With regard to the primary standard for particles generally less than or equal to 10 µm in diameter (PM 10 ), the EPA is retaining the current 24-hour PM 10 standard to continue to provide protection against effects associated with short-term exposure to thoracic coarse particles (i.e., PM 10-2.5 ). With regard to the secondary (welfare-based) PM standards, the EPA is generally retaining the current suite of secondary standards (i.e., 24-hour and annual PM 2.5 standards and a 24-hour PM 10 standard). Non-visibility welfare effects are addressed by this suite of secondary standards, and PM-related visibility impairment is addressed by the secondary 24-hour PM 2.5 standard.

Notice is hereby given that the EPA has posted its draft non-binding guidance titled, Draft Guidance to Implement Requirements for the Treatment of Air Quality Monitoring Data Influenced by Exceptional Events and associated attachments, on the agency's Internet Web site. The EPA invites public comments on this guidance document and plans to issue an updated version of the guidance after reviewing timely submitted comments. The EPA intends to hold a conference call to provide interested stakeholders with an overview of the Exceptional Events draft guidance.

The EPA is announcing two public hearings for the proposed rule titled, “National Ambient Air Quality Standards for Particulate Matter,” that is scheduled to be published in the Federal Register on June 29, 2012. The hearings will be held in Philadelphia, Pennsylvania, and Sacramento, California. In this rulemaking, the EPA is proposing to make revisions to the primary and secondary national ambient air quality standards (NAAQS) for particulate matter (PM) to provide requisite protection of public health and welfare, respectively, and to make corresponding revisions to the data handling conventions for PM and ambient air monitoring, reporting, and network design requirements. The EPA is proposing changes to the Air Quality Index (AQI) to be consistent with the proposed primary standards. In addition, the EPA is proposing revisions to the prevention of significant deterioration (PSD) permitting program with respect to the proposed NAAQS revisions.