40 CFR § 52.121 - Classification of regions.

---
identifier: "/us/cfr/t40/s52.121"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 52.121 - Classification of regions."
title_number: 40
title_name: "Protection of Environment"
section_number: "52.121"
section_name: "Classification of regions."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "52"
part_name: "APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401"
cfr_part: "52"
---


# 52.121 Classification of regions.

The Arizona plan is evaluated on the basis of the following classifications:

|  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| 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]