40 CFR 52.2471: Classification of regions.

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