The Oregon plan was evaluated on the basis of the following classifications:
Air quality control region | Pollutant | ||||
Particulate matter | Sulfur oxides | Nitrogen dioxide | Carbon monoxide | Ozone | |
Portland Interstate | I | IA | III | I | I |
Southwest Oregon Intrastate | II | III | III | III | III |
Northwest Oregon Intrastate | III | III | III | III | III |
Central Oregon Intrastate | II | III | III | III | III |
Eastern Oregon Intrastate | II | III | III | III | III |
40 C.F.R. §52.1971