The Washington plan was evaluated on the basis of the following classifications:
| Air quality control region
| Pollutant
|
|---|
| Particulate matter
| Sulfur oxides
| Nitrogen
dioxide
| Carbon
monoxide
| Ozone
|
|---|
| Eastern Washington-Northern Idaho Interstate | I | IA | III | III | III
|
| Northern Washington Intrastate | II | III | III | III | III
|
| Olympic-Northwest Washington Intrastate | II | II | III | III | III
|
| Portland Interstate | I | IA | III | III | III
|
| Puget Sound Intrastate | I | IA | III | III | I
|
| South Central Washington Intrastate | I | III | III | III | III |