Under the Clean Air Act, EPA is required to periodically review and, if appropriate, revise the air quality criteria and national ambient air quality standards (NAAQS). On April 18, 2018, the EPA published a final action in which the Agency retained the primary (health-based) NAAQS for oxides of nitrogen without revision. The current review includes the preparation of an Integrated Review Plan, an Integrated Science Assessment, risk and exposure analyses, as warranted, and also a Policy Assessment by EPA, with opportunities for review by EPA’s Clean Air Scientific Advisory Committee (CASAC), at public meetings, and by the public, announced at stakeholder meetings, EPA’s website and in the Federal Register. Opportunities for public participation in the development of these documents include through the offering of comments to the CASAC at public CASAC meetings and directly to the EPA. These documents inform the Administrator’s proposed decision as to whether to retain or revise the standards. This decision will be published in the Federal Register, and announced on EPA’s website, with opportunity provided for public comment. Opportunities for public participation at this stage include, as requested, via Tribal consultation or public hearing, as well as the submission of comments to the rulemaking docket. The Administrator’s final decisions will take into consideration the review documents and public comment on the proposed decision.