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The U.S. Environmental Protection Agency this week finalized a ruling that shields the Phoenix-Mesa region from a more stringent federal air quality classification, delivering a significant win for Arizona businesses and capping a years-long effort to address a problem the state has long argued it didn’t cause.

The EPA determined that the Phoenix-Mesa area would have met federal ozone standards by its August 2024 deadline but for pollution coming in from outside the United States. Under a provision of the Clean Air Act known as Section 179B, the agency will not reclassify the region from “Moderate” to “Serious” nonattainment.

The distinction matters. A reclassification to “Serious” would have significantly tightened the regulatory screws on businesses 鈥� lowering thresholds for major emission sources, increasing offset requirements, and expanding air quality control obligations 鈥� all while adding complexity to permitting.

The case for the exemption rested on a straightforward argument backed by years of modeling: Phoenix’s ozone problem is largely not of Phoenix’s making. Independent modeling by both the Maricopa Association of Governments and the EPA found that approximately 80 percent of the ozone in the region comes from natural sources or emission sources outside the nonattainment area, including pollution transported from Mexico and Asia, and wildfire smoke.

MAG, the regional planning agency for metropolitan Phoenix, said it had been advocating for the exemption since the Biden administration. It formally submitted its demonstration to EPA in September 2025, and the Phoenix ruling marks the first time the EPA has used its Section 179B authority since Administrator Lee Zeldin rescinded prior guidance that had made the process difficult for states to navigate.

Danny Seiden, president and CEO of the Arizona Chamber of Commerce & Industry, called the outcome long overdue. “For decades, Arizona’s businesses have done everything right,” Seiden said. “They’ve invested in cleaner operations, embraced new technology, and helped cut the region’s air pollution by roughly 70 percent since 1990 鈥� all while our economy and population grew dramatically.”

The National Association of Manufacturers weighed in quickly after the ruling, saying the EPA decision gives Arizona’s manufacturers greater flexibility to grow while advancing environmental stewardship. The NAM also called on Congress to build on the momentum by modernizing the Clean Air Act’s permitting process, noting that manufacturers consistently cite Clean Air Act permits as the most burdensome approval process they face.

said the ruling reflects the agency’s broader approach under Administrator Zeldin. “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,” Martucci said.

Under the final determination, the Phoenix-Mesa area remains classified as Moderate nonattainment and is not subject to reclassification requirements or the more burdensome permitting and offset requirements that would have come with a Serious designation. All other existing Moderate area obligations remain in effect.

Seiden said the Chamber would continue to watch the ruling closely. “We stand ready to vigorously defend this decision against any effort to undo it,” he said.