SUPPLEMENTARY INFORMATION:

Docket. The EPA has established a docket for this action under Docket ID No. EPA-HQ-OAR-2024-0078. All documents in the docket are listed in www.regulations.gov. Although listed, some information is not publicly available, e.g., Confidential Business Information (CBI) or other information the disclosure of which is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available as PDF versions that can only be accessed on the EPA computers in the docket office reading room. Certain databases and physical items cannot be downloaded from the docket but may be requested by contacting the docket office at (202) 566-1744. With the exception of such material, publicly available docket materials and a plain language summary of the action are available electronically at www.regulations.gov.

Written Comments. Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2024-0078, at www.regulations.gov (the EPA's preferred method) or the other methods identified in the ADDRESSES section. Once submitted, comments cannot be edited or removed from the docket. The EPA will publish any comment received to the Agency's public docket. Do not submit to the EPA's docket at www.regulations.gov any information you consider to be CBI, Proprietary Business Information (PBI), or other information the disclosure of which is restricted by statute. This type of information should be submitted as discussed below. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( i.e., on the web, cloud, or other file sharing system). Please visit www.epa.gov/​dockets/​commenting-epa-dockets for additional submission methods; the full EPA public comment policy; information about CBI, PBI, or multimedia submissions; and general guidance on making effective comments.

Submitting CBI. Do not submit information containing CBI to the EPA through www.regulations.gov. Clearly mark the part or all of the information that you claim to be CBI. For CBI information on any digital storage media that you mail to the EPA, note the docket ID, mark the outside of the digital storage media as CBI, and identify electronically within the digital storage media the specific information that is claimed as CBI. In addition to one complete version of the comments that includes information claimed as CBI, you must submit a copy of the comments that does not contain the information claimed as CBI directly to the public docket through the procedures outlined in Written Comments section above. If you submit any digital storage media that does not ( printed page 63518) contain CBI, mark the outside of the digital storage media clearly that it does not contain CBI and note the docket ID. Information not marked as CBI will be included in the public docket and the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 Code of Federal Regulations (CFR) part 2.

Our preferred method to receive CBI is electronic transmission using email attachments, File Transfer Protocol (FTP), or other online file sharing services ( e.g., Dropbox, OneDrive, Google Drive). Electronic submissions must be transmitted directly to the Office of State Air Partnerships (OSAP) CBI Office at the email address osapcbi@epa.gov and, as described above, should include clear CBI markings and note the docket ID. If assistance is needed with submitting large electronic files that exceed the file size limit for email attachments, and if you do not have your own file sharing service, please email osapcbi@epa.gov to request a file transfer link. If sending CBI information through the postal service, please send it to the following address: U.S. Environmental Protection Agency, Attn: OSAP Document Control Officer, Mail Drop: C404-02, 109 T.W. Alexander Drive, P.O. Box 12055, Research Triangle Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2024-0078. The mailed CBI material should be double wrapped and clearly marked. Any CBI markings should not show through the outer envelope.

Preamble acronyms and abbreviations. Throughout this preamble, the use of “we,” “us,” or “our” is intended to refer to the EPA. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here:

CAA Clean Air Act

CBI Confidential Business Information

CFR Code of Federal Regulations

DV Design Value

EPA Environmental Protection Agency

FR Federal Register

FTP File Transfer Protocol

NAAQS National Ambient Air Quality Standard or Standards

OSAP Office of State Air Partnerships

PBI Proprietary Business Information

PM Particulate Matter

SIP State Implementation Plan

TAS Treatment in a Similar Manner as a State

U.S.C. United States Code

Table of Contents

I. Overview of Action

II. Legal Authority

III. The EPA's Intended Approach to Area Designations

I. Overview

Under CAA section 107(d), the EPA is to issue area designations upon promulgation of a new or revised NAAQS. On February 7, 2024, the EPA promulgated revisions to the primary annual PM_2.5 NAAQS to a level of 9.0 micrograms per cubic meter (µg/m^[3] ) as described in 40 CFR 50.20.^[1] On July 17, 2026, the Northern District Court of California ordered the EPA to publish final designations for all areas of the country no later than February 6, 2027.^[2] Although EPA is appealing the order, EPA is also moving forward in the absence of action from the judiciary, to complete the designations.

As a general matter, the first step in the designations process is for the Governors of States and territories, and Tribes, if they so choose, to submit initial area designations to the EPA. Whenever the EPA intends to modify a Governor's initial designation, the Agency must notify the State, territory, or Tribe no later than 120 days prior to promulgating final designations.^[3] These notifications are informally referred to as 120-day letters.

This notice of availability provides notice of the EPA's intended approach for designations for the 2024 annual PM_2.5 NAAQS under CAA section 107(d)(1)(B). The EPA invites public input regarding area designations during the 30-day comment period announced in this notice. To receive full consideration, input from the public must be submitted to the docket by the date provided in the DATES section of this document. This notice and opportunity for public comment does not affect any rights or obligations of any State, territory, or Tribe, or of the EPA, which might otherwise exist pursuant to CAA section 107(d).

II. Legal Authority

Following promulgation of a new or revised NAAQS, CAA section 107(d) requires the EPA to designate areas of the country as attainment, nonattainment, or unclassifiable for that NAAQS. CAA section 107(d)(1)(A)(i)-(iii) defines: (i) nonattainment, as any area that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the NAAQS; (ii) attainment, as any area (other than an area identified in clause (i)) that meets the NAAQS; and (iii) unclassifiable, as any area that cannot be classified on the basis of available information as meeting or not meeting the NAAQS. Generally, the designations process involves identifying areas of the country that either meet or do not meet the NAAQS, along with any nearby areas that are causing or contributing to NAAQS violations. The EPA calculates design values (DVs) at monitors to determine whether a given area has met the 2024 annual PM_2.5 NAAQS, based on procedures outlined in 40 CFR part 50, Appendix N.^[4] The 2024 annual PM_2.5 NAAQS is met at an ambient air quality monitoring site when the annual arithmetic mean, averaged over three years ( i.e., the DV) is less than or equal to 9.0 µg/m³ .

In accordance with the statutory timeline prescribed under CAA section 107(d)(1)(A), Governors of each State or territory were required to submit a list of initial designations for all areas of their State or territory by February 7, 2025. Though not required, Tribal governments were encouraged to submit initial designations for their respective areas of Indian Country.^[5] These submissions generally relied on the 2021-2023 DVs and other information relevant to that time period. When promulgating final designations, the EPA will use the most recently available ambient air monitoring data and other information. The EPA intends to rely on DVs from the 2023-2025 period for promulgating final area designations.

The EPA evaluates the initial area designation submissions from States, ( printed page 63519) the District of Columbia, territories, and Tribes as part of the Agency's duty to promulgate final designations for a new or revised NAAQS. CAA section 107(d)(1)(B)(ii) provides that, whenever the EPA intends to modify an initial designation for a State, territory, or Tribe, the Agency must notify the State, territory, or Tribe no later than 120 days before the date the Administrator promulgates final designations. CAA section 107(d)(1)(B)(ii) further requires the EPA to provide such State with an opportunity to demonstrate why any potential modification is inappropriate. Although not required by the CAA, the EPA has issued letters notifying all States, the District of Columbia territories, and certain Tribes of EPA's intended approach for finalizing designations, including instances where the State, territory, or Tribe declined to submit an initial area designation. The EPA's 120-day letters requested that the States provide additional information to the Agency within 30 days of receipt of the letters.

III. The EPA's Intended Approach to Area Designations

A. What is the EPA's intended approach for area designations?

Consistent with CAA section 107(d)(1), the EPA has conducted an evaluation of the most recent and relevant air quality information available. This includes evaluation of the complete and certified PM_2.5 ambient air quality monitoring data, including the 2021-2023 DVs on which States, the District of Columbia, territories, and Tribes, based their initial designation submissions. Additionally, the EPA evaluated and utilized the most recent complete and certified PM_2.5 air quality monitoring data, including the 2023-2025 DVs, and other available technical information pertinent to these designations. Furthermore, the EPA considered the information submitted from States, the District of Columbia, territories, and Tribes in their initial area designations.

On or about October 2, 2026, in accordance with CAA section 107(d)(1)(B)(ii), the EPA completed its obligation to notify States of any intended modification to initial designations no later than 120-days prior to promulgating final designations. The EPA notified all States, the District of Columbia, territories, and certain Tribes as to whether the EPA intends to modify aspects of the State's initial designations for the 2024 annual PM_2.5 NAAQS. With respect to State initial designations that indicated “attainment,” and where the EPA functionally agrees with the State recommendation, the Agency intends to designate those States as “attainment/unclassifiable.” As a functional matter, there is no change for those States; the statutory and regulatory burdens of “attainment” and “attainment/unclassifiable” are the same.

Information may be submitted to the EPA's public docket regarding these intended designations at EPA-HQ-OAR-2024-0078, available at www.regulations.gov. Pursuant to CAA section 107(d)(1)(B) and following consideration of any additional information the EPA receives, the Agency anticipates completing final designations consistent with CAA requirements and in a timely manner commensurate with any applicable court order. The EPA is available to assist States, the District of Columbia, territories, and Tribes with any outstanding matters concerning appropriate designations for all remaining areas.

B. Where can I find information related to these designations?

Information is provided in the individual 120-day letters themselves and the dataset(s) included in the docket. The relevant datasets, technical assistance documents, applicable EPA guidance memoranda, and copies of correspondence regarding this process between the Agency and the States, along with other parties, are available for review at the public docket for these 2024 annual PM_2.5 NAAQS designations at www.regulations.gov under Docket ID No. EPA-HQ-OAR-2024-0078, at the EPA Docket Center listed in the FOR FURTHER INFORMATION CONTACT section of this document, and on the Agency's Particulate Matter Designations website at www.epa.gov/​particle-pollution-designations.

91 FR 63516