Environmental Protection Agency: Setting and Reviewing Standards to Control Ozone Pollution
Environmental Protection Agency

National Ambient Air Quality Standards (NAAQS) for ground-level ozone, or ozone pollution, specify a maximum allowed measurement for ozone (O3) to be present in outdoor air.

Environmental Protection Agency: Air Quality Designations for Ozone
Environmental Protection Agency

The Clean Air Act requires EPA to designate areas in the United States after the agency sets a new National Ambient Air Quality Standard (NAAQS) or revises an existing standard