U.S. Code of Federal Regulations
Regulations most recently checked for updates: Aug 28, 2025
The Michigan plan was evaluated on the basis of the following classifications:
| Air quality control region | Pollutant | ||||
|---|---|---|---|---|---|
| Particulate matter | Sulfur oxides | Nitrogen dioxide | Carbon monoxide | Ozone | |
| Metropolitan Detroit-Port Huron Intrastate | I | I | III | III | III |
| Metropolitan Toledo Interstate | I | I | III | III | I |
| South Central Michigan Intrastate | II | II | III | III | III |
| South Bend-Elkhart (Indiana)-Benton Harbor (Michigan) Interstate | I | IA | III | III | III |
| Central Michigan Intrastate | II | III | III | III | III |
| Upper Michigan Intrastate | III | III | III | III | III |
