Classification of regions.

The Ohio plan was evaluated on the basis of the following classifications: Air quality control region Pollutant Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Ozone Greater Metropolitan Cleveland Intrastate I I III III I Huntington (West Virginia)-Ashland (Kentucky)-Portsmouth-Ironton (Ohio) Interstate I III III III III Mansfield-Marion Intrastate II II III III III Metropolitan Cincinnati Interstate I II III III I Metropolitan Columbus Intrastate I III III III I Metropolitan Dayton Intrastate I II III III I Metropolitan Toledo Interstate I I III III I Northwest Ohio Intrastate II I III III III Northwest Pennsylvania-Youngstown Interstate I II III III III Parkersburg (West Virginia)-Marietta (Ohio) Interstate I II III III III Sandusky Intrastate III III III III III Steubenville-Weirton-Wheeling Interstate I I III III III Wilmington-Chillicothe-Logan Intrastate III III III III III Zanesville-Cambridge Intrastate II IA III III III [37 FR 10886, May 31, 1972, as amended at 39 FR 16347, May 8, 1974; 45 FR 72146, Oct. 31, 1980]