40 C.F.R. § 52.121
Classification of regions.
Cite as 40 C.F.R. § 52.121 (2026)
The Arizona plan is evaluated on the basis of the following classifications: AQCR (constituent counties) Classifications PM SO X NO 2 CO O 3 Maricopa Intrastate (Maricopa) I III III I I Pima Intrastate (Pima) I III III III III Northern Arizona Intrastate (Apache, Coconino, Navajo, Yavapai) I III III III III Mohave-Yuma Intrastate (La Paz, Mohave, Yuma) I III III III III Central Arizona Intrastate (Gila, Pinal) I IA III III I Southeast Arizona Intrastate (Cochise, Graham, Greenlee, Santa Cruz) I IA III III III [83 FR 42219, Aug. 21, 2018, as amended at 89 FR 71835, Sept. 4, 2024; 90 FR 59056, Dec. 18, 2025]