The USEPA is approving the State of Ohio's State Implementation Plan revision request to redesignate the Canton (Stark County), and Youngstown (Mahoning and Trumbull Counties) marginal ozone nonattainment areas to attainment, and establish ozone standard maintenance plans for these areas. Ground-level ozone, commonly known as smog, is an air pollutant which forms on hot summer days which harmfully affects lung tissue and breathing passages. The redesignation to attainment of the health-based ozone air quality standard is based on a request from the State of Ohio to redesignate this area and approve its maintenance plan, and on the supporting data the State submitted in support of the requests. Under the Clean Air Act, designations can be changed if sufficient data are available to warrant such change, and a maintenance plan is put in place which is designed to ensure the area maintains ozone air quality standard for the next ten years.