# Federal Register 2026-16989 — effective 2026-09-21 — Air Plan Approval; Arizona; Attainment Plan for the Hayden SO2 Nonattainment Area for the 1971 and 2010 Sulfur Dioxide National Ambient Air Quality Standards — Environmental Protection Agency

For Federal Register 2026-16989, effective date is 2026-09-21; agency is Environmental Protection Agency; published is 2026-08-20; cfr parts amended is 40 CFR 52; dates, as printed is This rule is effective September 21, 2026, recorded from its source on 2026-08-31; source re-checked 2026-09-16.

- **FR document number:** 2026-16989 _(verified: appears in the quote below)_
- **Rule:** Air Plan Approval; Arizona; Attainment Plan for the Hayden SO2 Nonattainment Area for the 1971 and 2010 Sulfur Dioxide National Ambient Air Quality Standards _(verified: appears in the quote below)_
- **Agency:** Environmental Protection Agency _(verified: appears in the quote below)_
- **Effective date:** 2026-09-21 _(verified: appears in the quote below)_
- **DATES, as printed:** This rule is effective September 21, 2026. _(verified: appears in the quote below)_
- **CFR parts amended:** 40 CFR 52 _(our reading, not quoted from the source)_
- **Published:** 2026-08-20 _(verified: appears in the quote below)_

## What the source says

> {"document_number":"2026-16989","title":"Air Plan Approval; Arizona; Attainment Plan for the Hayden SO2 Nonattainment Area for the 1971 and 2010 Sulfur Dioxide National Ambient Air Quality Standards","agency_names":["Environmental Protection Agency"],"effective_on":"2026-09-21","dates":"This rule is effective September 21, 2026.","cfr_references":[{"chapter":null,"citation_url":null,"part":"52","title":40}],"publication_date":"2026-08-20","html_url":"https://www.federalregister.gov/documents/2026/08/20/2026-16989/air-plan-approval-arizona-attainment-plan-for-the-hayden-so2-nonattainment-area-for-the-1971-and"}

## Source

- https://www.federalregister.gov/api/v1/documents.json?per_page=1000&order=oldest&conditions%5Btype%5D%5B%5D=RULE&conditions%5Beffective_date%5D%5Bgte%5D=2026-08-31&conditions%5Beffective_date%5D%5Blte%5D=2026-12-31&fields%5B%5D=document_number&fields%5B%5D=title&fields%5B%5D=agency_names&fields%5B%5D=effective_on&fields%5B%5D=dates&fields%5B%5D=cfr_references&fields%5B%5D=publication_date&fields%5B%5D=html_url

Last verified: 2026-09-16. Review by: 2026-09-29.
Part of [Federal rules taking effect: every US final rule in the Federal Register, by effective date](https://referencesource.org/federal-rules-taking-effect/).