---
kind: "section"
citation: "40 C.F.R. § 52.121"
title: "40"
number: "52.121"
heading: "Classification of regions."
url: "https://uscodex.org/cfr/40/52.121"
---

# §52.121. Classification of regions.


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


## Notes

### Amendments

[83 FR 42219, Aug. 21, 2018, as amended at 89 FR 71835, Sept. 4, 2024; 90 FR 59056, Dec. 18, 2025]

### Authority

Authority: 42 U.S.C. 7401 et seq.

### Amendments

[40 FR 5521, Feb. 6, 1975]

### Amendments

[83 FR 42219, Aug. 21, 2018, as amended at 89 FR 71835, Sept. 4, 2024; 90 FR 59056, Dec. 18, 2025]