52.1021—Classification of regions.
The Maine 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 Portland Intrastate | I | II | III | III | III |
| Androscoggin Valley Interstate | IA | IA | III | III | III |
| Down East Intrastate | IA | IA | III | III | III |
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| Aroostook Intrastate | III | III | III | III | III |
| Northwest Maine Intrastate | III | III | III | III | III |