Classification of regions.

The Idaho plan was evaluated on the basis of the following classifications: Air quality control region Pollutants Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Ozone Eastern Idaho Intrastate I II III III III. Eastern Washington Northern Idaho Interstate (Idaho) I II III III III. Idaho Intrastate I III III III III. Metropolitan Boise Intrastate II III III I III. [37 FR 10861, May 31, 1972, as amended at 45 FR 70261, Oct. 23, 1980; 47 FR 32534, July 28, 1982]