40 C.F.R. § 52.51
Classification of regions.
Cite as 40 C.F.R. § 52.51 (2026)
The Alabama 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) Alabama & Tombigbee Rivers Intrastate II III III III III Columbus (Georgia)-Phenix City (Alabama) Interstate I III III III III East Alabama Intrastate I III III III III Metropolitan Birmingham Intrastate I II III I I Mobile (Alabama)-Pensacola-Panama City (Florida)-Southern Mississippi Interstate I I III III I Southeast Alabama Intrastate II III III III III Tennessee River Valley (Alabama)-Cumberland Mountains (Tennessee) Interstate I I III III III [37 FR 10847, May 31, 1972]