52.2021—Classification of regions.
The Pennsylvania plan was evaluated on the basis of the following classifications:
| Air quality control region | Pollutant | ||||
|---|---|---|---|---|---|
| Particulate matter | Sulfur oxides | Nitrogen dioxide | Carbon monoxide | Ozone (hydrocarbons) | |
| Metropolitan Philadelphia Interstate | I | I | III | I | I |
| Northeast Pennsylvania-Upper Delaware Valley Interstate | I | II | III | III | III |
| South Central Pennsylvania Intrastate | I | II | III | III | III |
| Central Pennsylvania Intrastate | I | III | III | III | III |
| Southwest Pennsylvania Intrastate | I | I | III | I | I |
| Northwest Pennsylvania-Youngstown Interstate | I | II | III | III | III |