Regional Ozone Analyses

WESTAR-WRAP supports both policy-related work and technical analyses, along with related data resources, to assist states, Tribes, federal land managers, local air agencies, and the U.S. EPA in understanding current and evolving regional ozone air quality issues in the West.

Ozone in the West is influenced by a combination of local emissions, regional transport, wildfire activity, background ozone, and international sources, all of which require technical and policy approaches across jurisdictions.

The regional effort on ozone includes, but is not limited to:

• Facilitating coordination and information sharing among western air quality agencies, federal land managers, and EPA on ozone planning, implementation, and emerging policy and regulatory issues;
• Supporting collaboration on regional ozone issues, including interstate and international transport, exceptional events, background ozone, attainment demonstrations, and other air quality planning challenges;
• Identifying regional technical and policy needs and opportunities for shared analyses, tools, and resources; and
• Communicating developments in ozone science, policy, and regulation that may affect western air agencies.

To support these efforts, WESTAR-WRAP develops and maintains shared data resources, facilitates collaboration among member agencies, supports technical analyses, and provides access to information and analytical products that help member jurisdictions address ozone-related air quality challenges.

Ozone Planning & Policy Coordination

WESTAR-WRAP hosted an ozone panel during our Fall 2025 Business Meeting to discuss recent 179b work and demonstrations. The presentations from Utah Department of Air Quality, Maricopa Association of Governments, and the Denver-North Front Range Air Quality Council are linked here, along with the panel recording. 

• Intermountain West Ozone Challenges – Utah DAQ
• Ozone Nonattainment in the West – Maricopa Association of Governments
• Ozone Analysis and Planning Efforts on the Front Range of Colorado – Denver RAQC

The Phoenix area 179b demonstration was approved by EPA on March 23, 2026. The link to the final rule is here

On April 30, 2026, the proposed rule accepting Utah’s 179b demonstration was published.

Background Ozone

• Western Ozone NAAQS Implementation Issues: Addressing Background and Transport; Uhl, M.A, and Moore, C.T., AWMA Environmental Manager, Sept. 2018
• Scientific assessment of background ozone over the U.S.: Implications for air quality management, Jaffe, D.A., et. al., July 2018 (supplemental material)

Western Modeling Studies (data for some studies are available on the Air Data Management System)