The U.S. Environmental Protection Agency announced on April 7 that the Phoenix-Mesa area will not be reclassified from Moderate to Serious nonattainment under the 2015 Ozone National Ambient Air Quality Standards. The agency cited Section 179B of the Clean Air Act, determining that emissions from outside the United States prevented the area from meeting federal ozone standards by its August 3, 2024 deadline.
According to EPA Acting Regional Administrator Mike Martucci, "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. 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."
EPA Assistant Administrator for Air and Radiation Aaron Szabo said, "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. 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 federal law, areas failing to meet ozone standards by their attainment date are typically reclassified, triggering more stringent requirements. However, Section 179B allows exemptions if international emissions are found responsible for nonattainment. The agency noted that prior guidance made it difficult for states to demonstrate foreign pollution impacts but said this changed after Administrator Lee Zeldin rescinded previous guidance on April 7, pledging greater cooperation with state and local agencies.
The Maricopa Association of Governments submitted evidence on September 24 showing that Phoenix-Mesa would have met standards without international emissions. This marks the first use of Section 179B authority since changes in guidance were implemented. As a result, Phoenix-Mesa avoids stricter permitting and emission offset requirements associated with a Serious classification; however, all other Moderate nonattainment requirements remain in effect.
EPA established its current ozone standard at 70 parts per billion in 2015 for public health protection. The agency held a public comment period regarding this determination and says it remains committed to helping Phoenix-Mesa ultimately achieve full attainment according to the official roster page.
