This second draft 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) and secondary (welfare-based) national ambient air quality standards (NAAQS) for ozone (O3). It presents analyses and preliminary staff conclusions regarding the policy implications of the key scientific and technical information that informs this review.