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PHOENIX (March 25, 2026) – Did you know that our region has reduced local emissions of air pollutants by a combined 50 percent since 2000 despite rapid population and economic growth? For more than two decades, the Maricopa Association of Governments (MAG) has been working to identify and plan for data-driven solutions to reduce local air emissions and improve regional air quality. Meeting federal air quality standards is not only critical for public health, but also for the region's economic vitality. Percent Change in Gross Domestic Product, Vehicle Miles Traveled, Population and Total Air Emissions in the MAG Region (Phoenix MSA) since 2000.

Despite tremendous historic success in reducing emissions and improving air quality, the region has been at risk of not meeting federal ozone standards, largely due to emission sources the region has no control over. Modeling performed by MAG and the Environmental Protection Agency (EPA) indicates that approximately 80 percent of regional ozone is from natural sources or originates from outside of Arizona, providing significant challenges to further reducing regional ozone pollution. A portion of that 80 percent of ozone beyond our control comes from international emissions, namely Asia and Mexico.

In the 1990s, Congress included a provision in the Clean Air Act, known as Section 179B, which exempts nonattainment areas from being reclassified into stricter ozone classifications if a demonstration can be made that the area would have attained federal air quality standards but for emissions emanating from outside the United States. A recent final rule by EPA validated a September 2025 modeling demonstration submitted to EPA by MAG and found that the Maricopa nonattainment area would have indeed met the 2015 National Ambient Air Quality Standard for ozone, but for emissions coming from outside the United States - entitling the MAG region to the reclassification relief Congress intended under Section 179B of the Clean Air Act. 

Prior to the final rule, the MAG region faced the prospect of being reclassified from a “Moderate” nonattainment area to “Serious” nonattainment due to continued exceedances of the 2015 8-hour ozone NAAQS. If that had occurred, new mandatory stringent control requirements on business and industry would have been triggered, limiting the region’s ability to continue economic development while providing negligible benefits for air quality.

Thanks to the technical analysis led by MAG and in partnership with Maricopa County and the Arizona Department of Environmental Quality, those stricter and unnecessary control requirements have been avoided. The focus of MAG and partner agencies can now fully focus on advancing policy-relevant, and scientifically-supported solutions to meaningfully reduce the 20 percent of ozone that is under regional control.

“Regional growth, prosperity, and our quality of life are directly tied to the air we breathe. Without the foresight and leadership of past Regional Council Chairs Kate Gallego and Kevin Hartke, the innovative and technically advanced work that MAG submitted to the EPA might not have happened,” said Mayor of El Mirage and current MAG Regional Council Chair Alexis Hermosillo. ”The EPA’s final rule validates years of data analysis, planning and collaborative air quality efforts by MAG and its partners and allows us to continue our focus on local strategies that advance air quality outcomes.”

Key Facts:

• EPA determined the Maricopa nonattainment area would have attained 2015 ozone standards by the August 2024 deadline if not for international emissions. 
• The region remains classified as a Moderate nonattainment area under the 2015 ozone standard and avoids reclassification to Serious.
• The final rule removes the requirement to develop and submit new, additional ozone contingency measures under the Clean Air Act. 
• MAG’s Clean Air Act Section 179B(b) demonstration was submitted on September 24, 2025. 
• EPA’s final decision affirms MAG findings. 

Why It Is Important: 
The EPA’s decision recognizes that ozone levels in the MAG region are significantly influenced by emissions from sources beyond U.S. borders, not solely by local sources. By avoiding reclassification, the region avoids unnecessary and more stringent regulatory requirements that could impose additional costs and compliance burdens on local governments, businesses, and residents.