Classification of regions.

The Tennessee plan was evaluated on the basis of the following classifications: Air quality control region Pollutant Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Photochemical oxidants (hydrocarbons) Eastern Tennessee-Southwestern Virginia Interstate I I III III III Tennessee River Valley-Cumberland Mountains Intrastate I I III III III Middle Tennessee Intrastate I II III III I Western Tennessee Intrastate I III III III III Chattanooga Interstate I II III III III Metropolitan Memphis Interstate I III III III I [37 FR 10894, May 31, 1972, as amended at 39 FR 16347, May 8, 1974]