Classification of regions.

The Wisconsin plan was evaluated on the basis of the following classifications: Air quality control region Pollutant Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Ozone Duluth (Minnesota)-Superior (Wisconsin) Interstate I II III III III North Central Wisconsin Intrastate II III III III III Lake Michigan Intrastate II III III III III Southeast Minnesota-La Crosse (Wisconsin) Interstate II IA III III III Southern Wisconsin Intrastate II III III III III Southeastern Wisconsin Intrastate I II III III I Rockford (Illinois)-Jamesville-Beloit (Wisconsin) Interstate II III III III III Metropolitan Dubuque Interstate I III III III III [37 FR 10902, May 31, 1972, as amended at 39 FR 16348, May 8, 1974; 45 FR 2322, Jan. 11, 1980]