Classification of regions.

The Virginia 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 Valley of Virginia Intrastate I III III III III Central Virginia Intrastate I III III III III Northeastern Virginia Intrastate IA III III III III State Capital Intrastate I III III III I Hampton Roads Intrastate I II III III I National Capital Interstate I I III I I [37 FR 15090, July 27, 1972, as amended at 39 FR 16347, May 8, 1974]