Classification of regions.

The Kentucky plan was evaluated on the basis of the following classifications: Air quality control region Pollutant Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Photochemical oxidants (hydrocarbons) Appalachian Intrastate II III III III III Bluegrass Intrastate II III III III III Evansville (Indiana)-Owensboro-Henderson (Kentucky) Interstate I II III III III Huntington (West Virginia)-Ashland (Kentucky)-Portsmouth-Ironton (Ohio) Interstate I III III III III Louisville Interstate I I III III I Metropolitan Cincinnati Interstate I II III III I North Central Kentucky Intrastate II III III III III Paducah (Kentucky)-Cairo (Illinois) Interstate I II III III III South Central Kentucky Intrastate III III III III III [37 FR 10868, May 31, 1972, as amended at 39 FR 16346, May 8, 1974]