EPA Determines Phoenix-Mesa Area Will Not Be Unfairly Punished for International Emissions
Agency Finalizes Use of Clean Air Act International Transport Provision to Prevent Phoenix-Mesa from a Higher Non-Attainment Determination
Today, U.S. Environmental Protection Agency (EPA) finalized its determination to not reclassify the Phoenix-Mesa area from Moderate to Serious nonattainment under the 2015 Ozone National Ambient Air Quality Standards (NAAQS). Citing Section 179B of the Clean Air Act (CAA), EPA finds that the Phoenix-Mesa area would have met federal ozone air quality standards by its August 3, 2024, deadline had it not been for emissions coming to the area from outside the United States. The agency’s decision will ensure that manufacturers and citizens in the Phoenix-Mesa area are not punished for emissions out of their control.
“This action is yet another example of the Trump EPA making sure we are not punishing Americans for emissions from countries that do not have our same environmental standards,” said EPA Acting Regional Administrator Mike Martucci. “Cooperative federalism is a key pillar of this EPA, and while the Phoenix-Mesa area continues working toward cleaner air, it is important EPA works with them. EPA stands ready to help the area achieve attainment.”
“We are proud to work with Maricopa Association of Governments to ensure that Phoenix-Mesa is not economically harmed by air emissions they have no control over,” said EPA Assistant Administrator for Air and Radiation Aaron Szabo, “We look forward to working with other EPA Regions and state and local governments around the United States to utilize all provisions under the Clean Air Act to ensure that we can continue to grow our economy while protecting our air quality.”
Under the CAA, areas that fail to attain the federal ozone air quality standards by their attainment date are reclassified to a higher nonattainment level, which triggers more stringent requirements. However, CAA Section 179B allows EPA to exempt areas from reclassification when the agency determines that a nonattainment area would have met its attainment requirement if it were not for the interference of international emissions. Prior to EPA Administrator Lee Zeldin’s leadership, states had an unnecessarily difficult time demonstrating that foreign air pollution harmed Americans within their borders and their ability to achieve attainment because of unworkable guidance. On April 7, 2025, Administrator Zeldin rescinded the Guidance on the Preparation of Clean Air Act Section (CAA) 179B Demonstrations for Nonattainment Areas Affected by International Transport of Emissions and pledged that through cooperative federalism the agency would work with state and local air agencies to develop the evidence necessary to grant regulatory relief under CAA Section 179B.
On September 24, 2025, the Maricopa Association of Governments submitted adequate evidence demonstrating that the area would have otherwise attained federal air quality standards by the statutory deadline. Today’s determination marks the first time EPA has used Section 179B authority since Administrator Zeldin rescinded the burdensome 179B guidance.
As a result of this determination, the Phoenix-Mesa area is not subject to reclassification requirements, nor the additional more difficult permitting and emission offset requirements of a Serious nonattainment classification. Additionally, requirements for the State of Arizona to submit contingency measures for attainment and reasonable further progress no longer apply to this area. All other requirements for a Moderate ozone nonattainment area continue to apply. EPA is committed to providing clean air for all Americans and working with the Phoenix-Mesa area to ultimately achieve attainment. EPA held a 30-day public comment period on the proposal regarding Phoenix-Mesa's attainment status.
Background
EPA established the 2015 Ozone NAAQS standards at 70 parts per billion to protect public health and the environment. The Phoenix-Mesa area is designated as nonattainment for this standard and had a Moderate attainment date of August 3, 2024.
Learn more about the Clean Air Act and NAAQS.
Learn about EPA’s Pacific Southwest Region. Connect with us on Facebook, Instagram, and X.