EPA Research Partner Support Story: Mitigating Rising Ozone Concentrations

EPA Research Partner Support Story: Mitigating Rising Ozone Concentrations is sponsored by U.S. Environmental Protection Agency (EPA). EPA collaborates with Arizona Department of Environmental Quality and other partners to address increasing ground-level ozone levels in Arizona.

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Partners: Arizona Department of Environmental Quality (ADEQ) , Maricopa County, Maricopa Association of Governments (MAG), Arizona State University and the University of Arizona Challenge: Identifying strategies to mitigate rising ground-level ozone concentrations in Arizona that pose significant health risks to residents Resource: Measurements, modeling, and analysis for state and local air quality officials to help understand the causes of rising local ozone concentrations and develop effective air quality management strategies to decrease local ozone Project Period : 2025 – Present Areas surrounding Phoenix, Arizona are partnering with EPA ORD to address an urgent issue of increasing levels of ground-level ozone, which cause health risks such as asthma attacks.

People most at risk include children, the elders, and outdoor workers. Maricopa County, the 4 th most populous county in the nation, and parts of Pinal County sometimes fail to meet federal air quality standards set to protect public health. "Arizona isn’t waiting for solutions to come from somewhere else — we’re partnering with EPA’s Office of Research and Development to tackle our ozone challenges head-on.

Their expertise is instrumental to gaining a deeper understanding of ozone formation in our unique environment. Through the GLOR Project, we’re creating a scientific framework that can inform air quality management strategies here in Arizona and across the nation.

” ‒ ADEQ Director Karen Peters Ground-level ozone is not emitted directly into the air but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). These “precursor” pollutants are locally emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources, and, in the presence of sunlight – found in abundance in Arizona – react to form ozone.

Despite significant progress in reducing local precursor emissions, there have been recent increases in ozone pollution. The Arizona DEQ, through the Ground Level Ozone Research (GLOR) project, is bringing together air quality experts and scientists to understand why ozone concentrations are not decreasing as much as expected.

The GLOR project includes EPA ORD and Region 9 (Pacific Southwest), NASA’s Jet Propulsion Laboratory, Maricopa County, Maricopa Association of Governments, Arizona State University, and the University of Arizona. Together, this skilled team will investigate local atmospheric transport, precursor emission rates, and chemical transformations and inform effective mitigation measures.

With ORD’s support, the GLOR team will develop a science-backed plan to reduce ozone in the Phoenix area, improving air quality for millions of residents. EPA Research to Support States Contact Us About EPA Research to Support States Contact Us About EPA Research to Support States to ask a question, provide feedback, or report a problem. Last updated on April 7, 2026