This Policy Assessment (PA) has been prepared by staff in the Environmental Protection Agency's (EPA) Office of Air Quality Planning and Standards (OAQPS) as part of the Agency's ongoing review of the primary (health-based) national ambient air quality standards (NAAQS) for oxides of nitrogen (referred to herein as the N02 NAAQS). It presents analyses and staff conclusions regarding the policy implications of the key scientific and technical information that informs this review. The PA is intended to "bridge the gap" between the relevant scientific evidence and technical information and the judgments required of the EPA Administrator in determining whether to retain or revise the current standards. Development of the PA is also intended to facilitate advice and recommendations on the standards to the Administrator from an independent scientific review committee, the Clean Air Scientific Advisory Committee (CASAC), as provided for in the Clean Air Act (CAA). Staff's conclusions in this PA are informed by consideration of the scientific evidence summarized and assessed in the Integrated Science Assessment for Oxides of Nitrogen-Health Criteria (ISA) and updated analyses comparing ambient nitrogen dioxide (N02) concentrations to health-based benchmarks, included herein. Emphasis is given to considering the extent to which the evidence newly available since the last review alters conclusions drawn in the last review with regard to health effects related to N02 exposures, the exposure concentrations at which those effects occur, and populations that may be at increased risk for effects.