SUPPLEMENTARY INFORMATION:

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

CAA or Act Clean Air Act

CARB California Air Resources Board

EPA or Agency Environmental Protection Agency

MSM most stringent measures

NAAQS national ambient air quality standards

PM2.5 particulate matter less than or equal to 2.5 µm in diameter

SCAQMD or District South Coast Air Quality Management District

SIP State implementation plan

Table of Contents

I. Executive Summary

A. What Action is the EPA Taking?

B. What is the Legal Authority and What are the Requirements?

II. Background and Summary of the Proposed Action

III. Public Comments and Responses

IV. Final Action

V. Statutory and Executive Order Reviews

I. Executive Summary

A. What action is the EPA taking?

The EPA is granting an extension of the Serious area attainment date for the South Coast Air Basin nonattainment area for the 2012 PM_2.5 NAAQS from December 31, 2025, to December 31, 2030, based on a determination that the State has satisfied the statutory criteria for this extension.

B. What is the Legal Authority and what are the requirements?

The EPA is granting the State's request for an attainment date extension pursuant to CAA section 188(e).

Under section 188(e) of the Act, a State may apply to the EPA for an extension of the Serious area attainment date by up to five years, which the EPA may grant if the State satisfies certain conditions. Before the EPA may extend the attainment date for a Serious area under CAA section 188(e), the State must:

(1) Demonstrate that attainment by the Serious area attainment date is impracticable;

(2) Demonstrate that it has complied with all requirements and commitments ( printed page 62317) pertaining to the area in the implementation plan;

(3) Demonstrate to the satisfaction of the Administrator that the plan for the area includes the “most stringent measures” (MSM) that are included in the implementation plan of any State or are achieved in practice in any State, and can feasibly be implemented in the area;

(4) Submit a modeled attainment demonstration showing attainment of the NAAQS in the area by the most expeditious alternative date practicable; and

(5) Apply for an extension of the attainment date beyond the Serious area attainment date.^[1]

II. Background and Summary of the Proposed Action

On June 11, 2026,^[2] the EPA proposed to grant a request from the State of California, submitted to the EPA on August 6, 2024,^[3] for an extension of the Serious area attainment date for the 2012 annual PM_2.5 NAAQS for the South Coast Air Basin from December 31, 2025, to December 31, 2030. We proposed to grant the State's request for an extension of the area's attainment date based on a proposed determination that the State has satisfied the requirements for such extensions in Clean Air Act (CAA or “Act”) section 188(e). In our proposed rule, we provided background information on the PM_2.5 NAAQS, area designations and related State implementation plan (SIP) revision requirements under the CAA, relevant EPA guidance, and the EPA's implementing regulations for the PM_2.5 NAAQS, referred to as the “PM_2.5 SIP Requirements Rule.” ^[4] The proposed rule also provided a detailed discussion of the rationale for our proposed action.^[5]

III. Public Comments and Responses

The public comment period for the proposed rulemaking opened on June 11, 2026, the date of its publication in the Federal Register , and closed on July 13, 2026.^[6] During this period, the EPA received two comment submissions from individual members of the public ^[7 8] and a comment submission from SCAQMD.^[9] Additionally, SCAQMD notified the EPA via email of a typographical error in the proposed action.^[10] The three comment submissions and email from SCAQMD are included in the docket for this action. The comment submission from SCAQMD is supportive of the EPA's proposal to grant the attainment date extension and does not require a response. Additionally, one of comments received from the public is not germane to our action and also does not require a response.^[11] A summary of the remaining comment submissions and our responses thereto follow.

Comment 1: The commenter states that the “population-exposed” factor under CAA section 188(e) “does not receive comparable treatment in the preamble” to the other discretionary CAA section 188(e) factors and that such factor “warrants an explicit finding.” The commenter asserts that the monitoring data in Table 2 of the EPA's proposal “shows the highest design values [are] concentrated at sites historically associated with environmental justice communities. . .[and] the record would benefit from an affirmative statement of who is exposed at the highest concentrations and for how long the extension leaves them there.” The commenter acknowledges that this factor is discretionary but asserts that “its omission from the preamble leaves no basis in the record for evaluating the extension's distributional impact,” and requests that the EPA supplement the record.

Response 1: As discussed in our proposal, the “population exposed to concentrations in excess of the standard” is among five factors identified in CAA section 188(e) that “the Administrator may consider” when determining whether to grant an attainment date extension for a Serious PM_2.5 nonattainment area.^[12] The proposal details the nature and extent of the nonattainment problem in the South Coast nonattainment area and the technological and economic feasibility of additional measures given the measures already adopted by CARB and the District. We concluded that “[t]hese factors generally support a longer time frame for attainment.” Because consideration of these additional factors in approving an attainment date extension under CAA section 188(e) is discretionary, we believe that the record in our proposal is sufficient to approve the extension.

Nonetheless, as discussed in the EPA's proposal and as required pursuant to CAA section 188(e), California's request for an attainment date extension for the South Coast Air Basin for the 2012 PM_2.5 NAAQS was accompanied by a revised attainment plan for the area, referred to herein as the 2024 South Coast PM_2.5 Plan. To meet the attainment planning requirements of the Act, the Plan includes, among other things, information on the spatial distributions of PM_2.5 concentrations across the nonattainment area, both historically and as projected in the future.^[13] Additionally, although not required, Chapter 7 of the Plan, includes the State's analysis of the distribution of air quality impacts across the South Coast Air Basin on various communities.^[14] The 2024 South Coast PM_2.5 Plan is included in the docket and is therefore ( printed page 62318) part of the record for this action. Thus, this information has been publicly available as the Agency has considered the State's extension request. It was also publicly available during the State's public process.

Comment 2: The commenter requests clarification regarding the connection between the EPA's action on the extension request and the pending review of the attainment demonstration. The commenter notes that the EPA's proposed rule does not provide a docket number or expected timeline for action on the Plan and asserts that the record would be strengthened by providing such information “so the public can track whether the underlying 2030 demonstration is confirmed before the extension period elapses.”

Response 2: As noted in the EPA's proposed action, the CAA does not require the EPA to act on the submitted attainment demonstration as a precondition to granting the extension, and we intend to act on the 2024 South Coast PM_2.5 Plan in a future action.^[15] The EPA is reviewing the submitted attainment plan for the South Coast for the 2012 annual PM_2.5 NAAQS. We will solicit public comment on our proposed action on the Plan, and the EPA's proposed action will be made available at www.regulations.gov and will include a docket number for submitting and tracking public comment submissions.

Comment 3: Noting that the four measures adopted by the District to meet the MSM requirement must be fully implemented by January 1, 2030, the commenter asserts that there is limited time between when the measures must be implemented and when the effects of these measures will be assessed ( i.e., the proposed December 31, 2030 extended attainment deadline). The commenter asks that the EPA “consider requesting or committing to an interim reporting checkpoint, such as a 2028 progress update, so that emissions performance data can inform course correction well before the extension period closes rather than only at its end.”

Response 3: As discussed in the EPA's proposed action, the EPA has interpreted the Act to require implementation of MSM as expeditiously as practicable and no later than one year before the extended Serious area attainment date identified by the State in its extension request.^[16] In this case, the State requested an extension of the attainment date under CAA section 188(e) to December 31, 2030. Thus, the State must provide for implementation of MSM no later than January 1, 2030.

To that end, we note that all four of the measures identified as MSM in the Plan are in effect in the South Coast Air Basin as the SCAQMD began implementing and enforcing the measures following approval by its Governing Board on September 5, 2025.^[17] Specifically, amendments to Rule 445 and the Rule 1133 series, amended to achieve additional PM_2.5 reductions pursuant to control measures BCM-18 and BCM-10, respectively, are already being fully implemented. Amendments to Rules 223 and 1138, amended to achieve additional PM_2.5 reductions pursuant to control measures BCM-08 and BCM-12, respectively, do include future compliance dates; however, all future compliance dates in these rules occur before the January 1, 2030 MSM implementation deadline.

Additionally, where the rule amendments include future compliance dates, SCAQMD's staff reports accompanying the rule amendments explain the District's justification for the later deadline. For example, SCAQMD explains that Rule 223 establishes a separate compliance timeline for the newly affected dairy facilities to allow sufficient time for these facilities to prepare and submit a permit application per the requirement in the rule,^[18] and that the 12-month grace period extending the exemption thresholds in Rule 1138 was included to provide owners or operators of chain-driven charbroilers time to acquire compliant equipment.^[19] We find these justifications to be reasonable and that the Plan provides for implementation of MSM as expeditiously as practicable.

To the extent that the commenter is concerned about the emissions reductions from these measures being achieved as envisioned, we note that CAA section 189(c) requires that the State's attainment plan for the South Coast for the 2012 PM_2.5 NAAQS contain quantitative milestones which are to be achieved every three years until the area is redesigned attainment and which demonstrate reasonable further progress toward attainment by the applicable attainment date. Quantitative milestones are required to provide an objective means to evaluate progress toward attainment. The CAA also requires a State to submit, within 90 days after each three-year quantitative milestone date, a milestone report that includes technical support sufficient to document completion statistics for appropriate milestones.

The State discusses its quantitative milestones to demonstrate continued compliance with the SIP for the South Coast for the 2012 PM_2.5 NAAQS in Chapter 6 (“Federal Clean Air Act Requirements”) of the 2024 South Coast PM_2.5 Plan. The plan includes quantitative milestones for the years 2025, 2028, and 2031. With regard to a progress update in 2028 requested by the commenter, we note that SCAQMD has committed to report on the “[a]doption and implementation of applicable PM_2.5 Plan measures according to the schedule specified in Chapter 4,” which includes the four MSM measures listed in Table 4-2 and discussed in greater detail elsewhere in Chapter 4 (“Control Strategy”) of the Plan. Thus, the District has already committed to a 2028 interim checkpoint as requested by the commenter.

Comment 4: The commenter requests clarification on whether the EPA independently evaluated the State's choice of a December 31, 2030 attainment date as opposed to an earlier date or if the maximum extension was granted solely on the basis of the State's evaluation.

Response 4: As discussed in the EPA's proposal, CAA section 188(e) requires that at the time of its application for an attainment date extension, the State must submit a demonstration of attainment by the most expeditious alternative date practicable.^[20] For the purposes of evaluating the State's extension request for the South Coast for the 2012 PM_2.5 NAAQS, we reviewed the 2024 South Coast PM_2.5 Plan to ensure that it contains the requisite demonstration, including the State's demonstration of attainment by 2030 and analysis concluding that attainment by 2029 would not be possible. Based on our review of the 2024 South Coast PM_2.5 Plan, we find that the State had made such a submission.

Comment 5: In its email dated June 10, 2026, SCAQMD notes that the proposed rule contains a typographical error when referring to the Moderate ( printed page 62319) area plan commitment for the 2012 annual PM_2.5 NAAQS. Specifically, the EPA's proposal indicates that the EPA had approved the District's commitment to achieve 7 tpd of direct PM_2.5 emissions reductions by the 2022 reasonable further progress year, whereas SCAQMD notes that the proposal should have indicated 7 tpd of NO_X emissions reductions.

Response 5: The commenter correctly identifies a mistake in the proposal. While in several instances the EPA's June 11, 2026 proposal correctly refers to the commitment as having been for 7 tpd of NO_X emissions reductions, in one instance, the proposal indicates that the commitment was for 7 tpd of direct PM_2.5 emissions reductions.^[21] The reference to direct PM_2.5 instead of NO_X was in error.^[22] The EPA's evaluation of whether the State had complied with all requirements and commitments in the implementation plan was appropriately based on our analysis of the NO_X emissions reductions achieved in relation to the State's 7 tpd NO_X emissions reduction commitment. Thus, this error is harmless in that it did not have an impact on our determination. We appreciate the commenter bringing this mistake to our attention.

IV. Final Action

For the reasons discussed in this final action, the EPA is granting the State's request for an extension of the Serious area attainment date from December 31, 2025, to December 31, 2030, based on a conclusion that the State has satisfied the requirements for such an extension in CAA section 188(e).

V. Statutory and Executive Order Reviews

Additional information about these statutes and Executive orders can be found at www.epa.gov/​laws-regulations/​laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review

This action is not a significant regulatory action and was therefore not submitted to the Office of Management and Budget (OMB) for review.

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

This action is not an Executive Order 14192 regulatory action because this action is not significant under Executive Order 12866.

C. Paperwork Reduction Act (PRA)

This action does not impose an information collection burden under the PRA because this action does not impose additional requirements beyond those imposed by State law.

D. Regulatory Flexibility Act (RFA)

I certify that this action will not have a significant economic impact on a substantial number of small entities under the RFA. This action will not impose any requirements on small entities beyond those imposed by State law.

E. Unfunded Mandates Reform Act (UMRA)

This action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect small governments. This action does not impose additional requirements beyond those imposed by State law. Accordingly, no additional costs to State, local, or Tribal governments, or to the private sector, will result from this action.

F. Executive Order 13132: Federalism

This action does not have federalism implications. It will not have substantial direct effects on the States, on the relationship between the National Government and the States, or on the distribution of power and responsibilities among the various levels of government.

G. Executive Order 13175: Coordination With Indian Tribal Governments

This action does not have Tribal implications. It will neither impose substantial direct costs on federally recognized Tribal governments nor preempt Tribal law. Thus, Executive Order 13175 does not apply to this action.

H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

The EPA interprets Executive Order 13045 as applying only to those regulatory actions that concern environmental health or safety risks that the EPA has reason to believe may disproportionately affect children, per the definition of “covered regulatory action” in section 2-202 of the Executive order. This action is not subject to Executive Order 13045 because it does not concern an environmental health risk or safety risk.

I. Executive Order 13211: Actions that Significantly Affect Energy Supply, Distribution, or Use

This action is not subject to Executive Order 13211, because it is not a significant regulatory action under Executive Order 12866.

J. National Technology Transfer and Advancement Act (NTTAA)

Section 12(d) of the NTTAA directs the EPA to use voluntary consensus standards in its regulatory activities unless to do so would be inconsistent with applicable law or otherwise impractical. The EPA believes that this action is not subject to the requirements of section 12(d) of the NTTAA because application of those requirements would be inconsistent with the CAA.

K. Congressional Review Act (CRA)

This action is subject to the CRA, and the EPA will submit a rule report to each House of the Congress and to the Comptroller General of the United States. This action is not a “major rule” as defined by 5 U.S.C. 804(2).

L. Petitions for Judicial Review

Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be filed in the United States Court of Appeals for the appropriate circuit by November 30, 2026. Filing a petition for reconsideration by the Administrator of this final action does not affect the finality of this action for the purposes of judicial review, nor does it extend the time within which a petition for judicial review may be filed, and shall not postpone the effectiveness of such rule or action. This action may not be challenged later in proceedings to enforce its requirements ( see CAA section 307(b)(2)).

91 FR 62316