Rule2026-05601
Determination of Attainment by the Attainment Date But for International Emissions for the 2015 Ozone National Ambient Air Quality Standards; Phoenix-Mesa Nonattainment Area, Arizona
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
March 23, 2026
Effective
April 22, 2026
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA or "Agency") is taking final action to determine that the Phoenix-Mesa nonattainment area ("Phoenix-Mesa area") would have attained the 2015 ozone national ambient air quality standards (NAAQS or "standards") by the August 3, 2024 "Moderate" area attainment date, but for emissions emanating from outside the United States. As a consequence of this action, the Phoenix-Mesa area is not subject to the Clean Air Act (CAA) requirements pertaining to reclassification upon failure to attain and remains classified as a Moderate nonattainment area for the 2015 ozone NAAQS. This final action fulfills the EPA's statutory obligation to determine whether the Phoenix-Mesa area attained the NAAQS by the attainment date. As a result of this final action, the State is no longer required to submit attainment and reasonable further progress (RFP) contingency measures for this area.
Full Text
<html>
<head>
<title>Federal Register, Volume 91 Issue 55 (Monday, March 23, 2026)</title>
</head>
<body><pre>
[Federal Register Volume 91, Number 55 (Monday, March 23, 2026)]
[Rules and Regulations]
[Pages 13777-13781]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-05601]
-----------------------------------------------------------------------
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R09-OAR-2025-2833; FRL-13057-02-R9]
Determination of Attainment by the Attainment Date But for
International Emissions for the 2015 Ozone National Ambient Air Quality
Standards; Phoenix-Mesa Nonattainment Area, Arizona
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: The Environmental Protection Agency (EPA or ``Agency'') is
taking final action to determine that the Phoenix-Mesa nonattainment
area (``Phoenix-Mesa area'') would have attained the 2015 ozone
national ambient air quality standards (NAAQS or ``standards'') by the
August 3, 2024 ``Moderate'' area attainment date, but for emissions
emanating from outside the United States. As a consequence of this
action, the Phoenix-Mesa area is not
[[Page 13778]]
subject to the Clean Air Act (CAA) requirements pertaining to
reclassification upon failure to attain and remains classified as a
Moderate nonattainment area for the 2015 ozone NAAQS. This final action
fulfills the EPA's statutory obligation to determine whether the
Phoenix-Mesa area attained the NAAQS by the attainment date. As a
result of this final action, the State is no longer required to submit
attainment and reasonable further progress (RFP) contingency measures
for this area.
DATES: This rule is effective March 23, 2026.
ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-R09-OAR-2025-2833. All documents in the docket are
listed on the <a href="https://www.regulations.gov">https://www.regulations.gov</a> website. Although listed in
the index, some information is not publicly available, e.g.,
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, is not placed on the internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available through <a href="https://www.regulations.gov">https://www.regulations.gov</a>, or please
contact the person identified in the FOR FURTHER INFORMATION CONTACT
section for additional availability information. If you need assistance
in a language other than English or if you are a person with a
disability who needs a reasonable accommodation at no cost to you,
please contact the person identified in the FOR FURTHER INFORMATION
CONTACT section.
FOR FURTHER INFORMATION CONTACT: Karina O'Connor, EPA Region IX, 75
Hawthorne St., San Francisco, CA 94105; telephone number: (415) 972-
3498; email address: <a href="/cdn-cgi/l/email-protection#7718141819191805591c16051e19163712071659101801"><span class="__cf_email__" data-cfemail="1e717d717070716c30757f6c77707f5e7b6e7f30797168">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this document, the use of
``Agency,'' ``we,'' ``us,'' or ``our'' refers to the EPA.
Table of Contents
I. Summary of the EPA's Proposed Action
II. Public Comments and EPA Responses
III. Final Action
IV. Statutory and Executive Order Reviews
I. Summary of the EPA's Proposed Action
On November 19, 2025, the EPA proposed to find that the Phoenix-
Mesa area would have attained the 2015 ozone NAAQS of 0.070 parts per
million (70 parts per billion (ppb)) by the Moderate area attainment
date of August 3, 2024, but for emissions emanating from outside the
United States, and is therefore not subject to the CAA requirements
pertaining to reclassification upon failure to attain.\1\ We briefly
summarize the proposal in this section.
---------------------------------------------------------------------------
\1\ 90 FR 52019.
---------------------------------------------------------------------------
CAA section 181(b)(2)(A) requires that within six months following
the applicable attainment date, the EPA shall determine whether an
ozone nonattainment area attained the ozone standard based on the
area's Design Value (DV) as of that date. If the EPA determines that an
area failed to attain, then CAA section 181(b)(2)(A) requires the area
to be reclassified by operation of law to the higher of: (1) the next
higher classification for the area, or (2) the classification
applicable to the area's DV as of the determination of failure to
attain. CAA section 181(b)(2)(B) of the CAA requires the EPA to publish
the determination of failure to attain and accompanying
reclassification in the Federal Register no later than six months after
the attainment date.
The EPA originally designated and classified the Phoenix-Mesa area
as a Marginal ozone nonattainment area for the 2015 ozone NAAQS with an
attainment date of August 3, 2021.\2\ On October 7, 2022, the EPA
determined that the Phoenix-Mesa area did not attain the standard by
the Marginal attainment date, and thus the area was reclassified as
Moderate by operation of law, with an attainment date of August 3,
2024.\3\ Because a DV for this NAAQS is based on the three most recent,
complete calendar years of data, attainment must occur no later than
December 31 of the year prior to the attainment date (i.e., December
31, 2023, in the case of Moderate nonattainment areas for the 2015
ozone NAAQS with an August 3, 2024 attainment date). Therefore, the
EPA's determination for the Phoenix-Mesa area is based in part upon the
complete, quality assured, and certified ambient ozone air monitoring
data from calendar years 2021, 2022, and 2023. The DV for this period
is 80 ppb, indicating that the Phoenix-Mesa area did not attain the
2015 ozone NAAQS of 70 ppb by its August 3, 2024 attainment date.
---------------------------------------------------------------------------
\2\ 83 FR 25776 (June 4, 2018), effective August 3, 2018.
\3\ 87 FR 60897.
---------------------------------------------------------------------------
CAA section 179B(b) provides that where a state demonstrates to the
Administrator's satisfaction that an ozone nonattainment area would
have attained the NAAQS by the applicable attainment date but for
emissions emanating from outside the United States, that area shall not
be subject to the provisions of CAA section 181(b)(2).\4\ In the event
an air agency does not demonstrate to the Administrator's satisfaction
that it would have attained the NAAQS but for international emissions,
CAA section 179B(b) does not excuse that area from the provisions of
CAA section 181(b)(2).
---------------------------------------------------------------------------
\4\ Note that the statute cites to 42 U.S.C 7511(a)(2), but that
provision establishes ozone attainment deadlines for severe areas
under the 1-hour standard. The EPA has long interpreted the citation
in CAA section 179B(b) to be a scrivener's error that was supposed
to refer to 42 U.S.C. 7511(b)(2), which refers to consequences for
failure to attain by the attainment date. See 57 FR 13498, 13569, n.
41 (April 16, 1992).
---------------------------------------------------------------------------
On September 24, 2025, the Maricopa Association of Governments
(MAG) submitted to the EPA for review the ``MAG 2025 Clean Air Act
Section 179B(b) Retrospective Demonstration of the Impact of
International Emissions on Ozone Concentrations in the Maricopa
Nonattainment Area'' (``Demonstration'').\5\ Using several lines of
evidence, MAG evaluated the extent to which ambient ozone levels in the
Phoenix-Mesa area have been affected by international emissions. The
Demonstration includes a conceptual model of ozone formation in the
Phoenix-Mesa area including a discussion of the meteorological and
topographic conditions that influence ozone formation, modeling to
quantify international contribution, information about precursor
emissions and ozone air quality trends, and an analysis of the
transport patterns influencing the area. In addition, MAG provided
information to support the exclusion of data from days that it found to
be ``atypical wildfire exceedance days'' from the calculation of the
base DV and the relative response factors used to quantify the
international contribution in the modeling.
---------------------------------------------------------------------------
\5\ Letter dated September 24, 2025, from Ed Zuercher, Executive
Director, MAG, to Lee Zeldin, Administrator, EPA.
---------------------------------------------------------------------------
On November 19, 2025, the EPA proposed to find that MAG established
to the satisfaction of the Administrator that, consistent with CAA
section 179B(b), the Phoenix-Mesa area would have attained the 2015
ozone NAAQS by the Moderate area attainment date of August 3, 2024, but
for emissions emanating from outside the United States, and is
therefore not subject to the provisions of CAA section 181(b)(2)(A) and
therefore would not be reclassified based on failure to attain.\6\ The
EPA also proposed that, if the Agency were to finalize the proposed CAA
section 179B(b) determination, the State would no longer be required to
submit contingency measures under CAA
[[Page 13779]]
section 172(c)(9) for the Phoenix-Mesa 2015 ozone nonattainment area.
---------------------------------------------------------------------------
\6\ 90 FR 52019.
---------------------------------------------------------------------------
Please see our proposed rule and the associated technical support
documents (TSDs) \7\ for more information concerning the background for
this action and for a more detailed discussion of our evaluation of the
Demonstration and the rationale for our determination that the Phoenix-
Mesa area would have attained the 2015 ozone NAAQS by the Moderate area
attainment date of August 3, 2024, but for emissions emanating from
outside of the United States. These documents are included in the
docket for this action.
---------------------------------------------------------------------------
\7\ The EPA's ``Technical Support Document for Review of
Atypical Events on 2015 8-Hour Ozone Phoenix-Mesa, AZ Nonattainment
Area for the 179B(b) Demonstration'' (``Atypical Events TSD'') and
the ``EPA Evaluation of the Clean Air Act Section 179B(b)
Demonstration for the Phoenix-Mesa 2015 Ozone NAAQS Nonattainment
Area--Modeling and Impact of International Emissions Technical
Support Document'' (``179B(b) TSD'').
---------------------------------------------------------------------------
II. Public Comments and EPA Responses
The EPA's proposed action provided a 30-day public comment period.
The comment period opened on November 19, 2025, the date of publication
in the Federal Register, and closed on December 19, 2025. During this
period, we received a total of 69 comment submissions, 19 of which were
supportive of our proposed action, and 48 that were opposed. Two
comment submissions did not express either support or opposition. The
EPA has prepared a response to comments document (RTC) that summarizes
and responds to germane comments we received on this rulemaking. The
RTC and all comments received are included in the docket for this
rulemaking.
Commenters supporting the proposed rulemaking agreed with the
proposed determination that MAG had demonstrated that the Phoenix-Mesa
area would have attained the 2015 ozone NAAQS but for international
emissions. These commenters also supported the determination that, if
the EPA finalized the determination, the State would no longer be
required to submit attainment and RFP contingency measures. MAG also
provided additional information supporting the Demonstration as a part
of its comments on the proposal.
A number of commenters requested that the EPA use this rulemaking
to issue national guidance for areas affected by international
emissions and provided specific legal rationales and recommendations
for implementing 179B. We appreciate these comments and understand the
desire for issuance of guidance regarding the implementation of CAA
section 179B; however, as noted in the proposal, this rulemaking is
applicable only to the Phoenix-Mesa area. Therefore, comments and
recommendations related to potential future nationally applicable
guidance for CAA section 179B are outside the scope of this action.
The EPA also received comments opposing the proposed rulemaking.
Some commenters expressed overall opposition to the proposal, while
others specifically challenged the Agency's legal interpretations of
the CAA and prior rulemakings, the EPA's policy direction, and the
adequacy of technical aspects of the Demonstration. Several commenters
also opposed the proposal that the State would not be required to
submit attainment or RFP contingency measures if the EPA finalizes the
proposal on this issue. Commenters opposing the proposal also provided
additional information supporting their arguments. In the following
paragraphs, we provide a brief summary of our responses regarding some
of the key issues raised in adverse comments.
We do not agree with assertions by some commenters that the
proposal failed to provide a sufficient explanation for any changes in
policy and interpretation of CAA section 179B(b). Under FCC v. Fox
Television Stations, Inc., an agency's change in policy is permissible
if the agency acknowledges the change, believes it to be better, and
``show[s] that there are good reasons for the new policy.'' \8\ As
explained further in responses III.B.1. and III.B.3. of the RTC, the
EPA has both acknowledged any changes in interpretation and policy and
provided justification for those changes based on the wording of CAA
section 179B(b). As noted in the proposal, we no longer consider
specific characteristics as necessarily suggesting the need for a more
detailed demonstration with additional evidence. We also no longer
consider the weight of evidence more compelling when a CAA section 179B
demonstration shows that international contributions are larger than
when a demonstration shows that domestic contributions exceed
international contributions.\9\ Finally, we proposed to find that
states will no longer be expected to show that they could not attain
with on-the-books measures and potential reductions associated with
controls required to be implemented by the attainment date in order to
qualify for approval of a 179B(b) determination.\10\ With respect to
the proper interpretation of the statute, the EPA explained its
proposed view of the statute's requirements as relevant to this
decision.
---------------------------------------------------------------------------
\8\ 556 U.S. 502, 515 (2009).
\9\ 90 FR 52019, 52023.
\10\ Id.
---------------------------------------------------------------------------
We also do not agree with comments opposing our proposed
determination that, following a final determination under CAA section
179B(b), the State would no longer be required to submit contingency
measures for the Phoenix-Mesa 2015 ozone nonattainment area. As
described in response III.B.2. of the RTC, the commenters' arguments
conflate the requirements and consequences of actions under CAA
sections 179B(a) and 179B(b), ignore the exemption from milestone
compliance demonstrations requirements for Moderate Ozone nonattainment
areas in CAA section 182(g), and improperly rely on CAA section 172(e).
In addition, we do not agree with comments asserting that CAA
section 179B applies only to ``International border areas'' based on
the section's heading. While ``the title of a statute and the heading
of a section are tools available for the resolution of a doubt about
the meaning of a statute'' they will not ``override the plain words''
of a statute.\11\ The plain words of CAA section 179B(b) make the
provision available to ``any State'' that meets the relevant
requirements and do not limit its application to border areas. Thus,
even though the heading of the section could suggest that it only
applies to a subset of areas along international borders, the statutory
language within the section does not explicitly limit it to a subset of
states or areas. That interpretation is consistent with the plain
meaning of the term ``any.'' \12\ As further explained in response
III.C. of the RTC, the commenters' other arguments regarding the
purpose and legislative history of the provision similarly cannot
overcome the plain text of the Act.
---------------------------------------------------------------------------
\11\ Dubin v. United States, 599 U.S. 110, 120-21 (2023)
(internal citations and quotations omitted).
\12\ The Supreme Court has repeatedly explained that ``read
naturally, the word `any' has an expansive meaning, that is, `one or
some indiscriminately of whatever kind.''' United States v.
Gonzales, 520 U.S. 1, 5 (1997)(quoting Webster's Third New
International Dictionary 97 (1976)). See also Ali v. Bureau of
Prisons, 552 U.S. 214, 220 (2008).
---------------------------------------------------------------------------
Finally, we do not agree with comments arguing that there was
insufficient technical basis for approval of the Demonstration. As
discussed in the proposal, the 179B(b) TSD, and response IV.A. of the
RTC, the EPA has considered and weighed each piece of evidence in the
Demonstration. The primary piece of evidence provided by
[[Page 13780]]
MAG was photochemical source apportionment modeling, which indicated an
international anthropogenic contribution of 14 ppb to the 2021-2023 DV
in the Phoenix-Mesa area. When subtracted from the 2021-2023 DV of 80
ppb, this would be a DV that attains the 70 ppb standard. Other
photochemical modeling, including zero-out modeling performed by the
EPA and other zero-out modeling performed by MAG, indicated an
international anthropogenic contribution of 8.5-10.0 ppb to the
Phoenix-Mesa area 2021-2023 DV. Information regarding potential
wildfire influence on 31 exceedance days in 2021-2023 is supportive of
the overall weight of evidence, as discussed in response IV.F. of the
RTC, but is not relied upon to exclude particular days from the
photochemical modeling. MAG also provided emissions estimates that
ozone precursor emissions in the Phoenix-Mesa area are decreasing,
while emissions in Mexico are increasing. Air parcel transport provided
additional qualitative evidence of influence of emissions from Mexico
on the Phoenix-Mesa area. We considered and qualitatively weighed each
of these analyses based on their relevance to CAA section 179B and the
nature of international contributions in the Phoenix area, as described
in MAG's conceptual model. After considering all of these analyses, as
well as both the supportive and adverse comments, we reaffirm that the
weight of evidence supports the conclusion that the 2023 ozone DVs at
all monitoring sites in the Phoenix area would have been at or below 70
ppb but for the influence of international emissions. Therefore, we
conclude that the State \13\ has established to the satisfaction of the
Administrator that the Phoenix-Mesa area would have attained the 2015
ozone NAAQS but for emissions emanating from outside the United States.
---------------------------------------------------------------------------
\13\ As explained in response III.D. of the RTC, it is
appropriate for MAG to stand in the shoes of the ``State'' for
purposes of CAA section 179B(b) with respect to the Phoenix-Mesa
area.
---------------------------------------------------------------------------
III. Final Action
After reviewing the Demonstration and considering all comments
received during the public comment period, and based on the weight of
evidence, the EPA is finalizing its determination that the State has
established to the satisfaction of the Administrator that the Phoenix-
Mesa area would have attained the 2015 ozone NAAQS but for emissions
emanating from outside the United States. This final action fulfills
the EPA's statutory obligation under CAA section 181(b)(2)(A) to
determine whether the Phoenix-Mesa area attained the NAAQS by the
attainment date. As a result of this final action, the State is no
longer required to submit attainment and RFP contingency measures for
this area. The area will remain designated nonattainment and thus the
State must continue to comply with applicable requirements for a
Moderate ozone nonattainment area, other than the contingency measures
requirement, as discussed in responses III.B.1., III.B.2., and III.E.
of the RTC.
IV. Statutory and Executive Order Reviews
Additional information about these statutes and Executive Orders
can be found at <a href="https://www.epa.gov/lawsregulations/laws-and-executive-orders">https://www.epa.gov/lawsregulations/laws-and-executive-orders</a>.
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
Executive Order 14192 does not apply because this is not
significant regulatory action and it is therefore exempted from review
under Executive Order 12866.
C. Paperwork Reduction Act (PRA)
This action does not impose an information collection burden under
the PRA. This action does not impose any information collection
activities.
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. The
determination that the Phoenix-Mesa area would have attained the 2015
ozone NAAQS but for international emissions does not in and of itself
create any new requirements beyond what is mandated by the CAA.
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. The action imposes no enforceable duty on any state,
local, or Tribal governments, or the private sector.
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 States and Tribes, or on the distribution
of power and responsibilities among the various levels of government.
The division of responsibility between the Federal Government and
States for the purposes of implementing the NAAQS is established under
the CAA.
G. Executive Order 13175: Coordination With Indian Tribal Governments
This action has Tribal implications. However, it will neither
impose substantial direct compliance costs on federally recognized
Tribal governments, nor preempt Tribal law.
The EPA has identified areas of Indian country within the Phoenix-
Mesa area that would be potentially affected by this rulemaking.
Specifically, the Fort McDowell Yavapai Nation, Gila River Indian
Community of the Gila River Indian Reservation, Salt River Pima
Maricopa Indian Community of the Salt River Reservation, and Tohono
O'odham Nation have lands that are located within the boundaries of the
Phoenix-Mesa area.
The EPA notified potentially affected Tribes located within the
boundaries of the Phoenix-Mesa 2015 ozone nonattainment area upon
publication of the proposed rule. The EPA did not receive any comments
or requests for additional information from Tribes.
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)
This action does not involve technical standards.
[[Page 13781]]
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 May 22, 2026. This action may not be
challenged later in proceedings to enforce its requirements (see
section 307(b)(2)).
List of Subjects in 40 CFR Part 52
Environmental protection, Administrative practice and procedure,
Air pollution control, Designations and classification, Incorporation
by reference, Intergovernmental relations, Nitrogen oxides, Ozone,
Reporting and recordkeeping requirements, Volatile organic compounds.
Dated: March 12, 2026.
Michael Martucci,
Acting Regional Administrator, EPA Region IX.
[FR Doc. 2026-05601 Filed 3-20-26; 8:45 am]
BILLING CODE 6560-50-P
</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>Indexed from Federal Register on March 23, 2026.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.