Under the Clean Air Act, as amended, the EPA is required to review and if appropriate revise the air quality criteria for the primary (health-based) and secondary (welfare-based) national ambient air quality standards (NAAQS) every 5 years. On February 9, 2010, the EPA published a final rule revising the primary NO2 NAAQS to provide increased protection for public health. The EPA has now initiated the next review of the primary NO2 NAAQS. This review will include the preparation of an Integrated Review Plan, an Integrated Science Assessment, and, if warranted, a Risk/Exposure Assessment, and also a Policy Assessment by the EPA, with opportunities for review by the EPA's Clean Air Scientific Advisory Committee and the public. These documents inform the Administrator's proposed decision as to whether to retain or revise the current standards. This proposed decision will be published in the Federal Register with opportunity provided for public comment. The Administrator's final decisions will take into consideration these documents, CASAC advice, and public comment on the proposed decision.