40 C.F.R. § 52.921
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 |