U.S. Code of Federal Regulations
Regulations most recently checked for updates: Aug 27, 2025
The Maryland plans were evaluated on the basis of the following classifications:
| Air quality control region | Pollutant | ||||
|---|---|---|---|---|---|
| Particulate matter | Sulfur oxides | Nitrogen dioxide | Carbon monoxide | Ozone | |
| Cumberland-Keyser Interstate | I | I | III | III | III |
| Central Maryland Intrastate | II | II | III | III | III |
| Metropolitan Baltimore Intrastate | I | I | I | I | I |
| National Capital Interstate | I | I | III | I | I |
| Southern Maryland Intrastate | III | III | III | III | III |
| Eastern Shore Intrastate | II | III | III | III | III |
