Board of Directors – July 10, 2024: Air Quality Update – EPA Response

June 28, 2024

The Honorable Spencer Cox
Governor of Utah
350 N. State Street, Suite 200
Salt Lake City, Utah 84114-2220

Dear Governor Cox:

Thank you for your April 23, 2024, letter, to President Biden concerning the 2015 ozone national ambient air quality standard (NAAQS) and the challenges specific to Western states. I appreciate how important ozone implementation and attainment issues are to Arizona, Colorado, Utah, and Wyoming.

Your letter states that ozone NAAQS implementation and attainment is particularly complicated in Western states due to ozone and/or ozone precursor contributions from wildfire emissions, natural background, biogenic sources, international transport, population growth, and mobile sources. Specifically, you ask that the EPA collaborate with Western states to identify ways to account for air quality impacts from wildfires and wildfire mitigation strategies within the EPA’s Exceptional Events Rule.

The EPA recognizes the increasing challenges and human health impacts posed by wildfires and the importance of increasing the application of prescribed fire in a strategic and coordinated manner. In November 2023, the EPA, the United State Department of Agriculture, Department of Interior, and the Centers for Disease Control signed a Memorandum of Understanding to further interagency collaboration to reach land management and air quality goals. The EPA’s Exceptional Events Rule provides a pathway for exclusion of air quality data influenced by both wildfires and prescribed fires on wildland as exceptional events. The EPA recently developed three new products to improve and support the process of identifying and documenting exceptional events specific to wildland fire related events. We expect these tools to help states to identify and seek exclusion of certain data.

You also ask that the EPA work with states to identify a pathway to approve strong technical submissions under the Clean Air Act for communities that are not adjacent to the border but have ozone problems associated with emissions emanating from outside of the United States. I want to highlight the agency’s 2020 guidance for areas that would be able to attain and maintain, or would have attained, the national air quality standards but for emissions emanating from outside the United States. This guidance affirms the Agency’s position that the Clean Air Act provision on this topic is not restricted to areas adjoining international borders.1

You also ask that the EPA implement common-sense reforms to the Renewable Fuels Standard in ozone nonattainment areas where the Reid Vapor Pressure (RVP) waiver for gasoline containing 10 percent ethanol applies. The CAA provides states with a means to remove that waiver, and the EPA has worked with interested states on such an approach.2 In addition, the EPA also continues to engage in discussions with states on other novel strategies and measures for reducing emissions of ozone precursors, including voluntary mobile source emissions programs.

Your letter raises a concern about the impact of CAA highway sanctions on transportation projects that would reduce emissions. The EPA is committed to working with your state to adequately address the ozone planning requirements of the CAA. We have been actively engaging with your states and across the country to deliver on the Clean Air Act’s public health goals and avoid sanctions taking effect. It is worth noting that highway sanctions apply only to highway projects, and not to transit projects, and EPA has worked with the Federal Highway Administration to ensure that transportation projects that meet appropriate criteria to show they are reducing emissions are categorically exempt from highway sanctions.3

Implementing any NAAQS is a federal, state, and Tribal partnership to reduce harmful pollution. The EPA is committed to engaging with states early in the planning process to provide technical assistance and ensure timely approval of all plans meeting CAA requirements. We understand the implementation-related challenges that you raised in your letter and are committed to working with you to address those challenges.

Again, thank you for your letter. If you have questions, you are welcome to contact me, or your staff may contact Michelle Marchello, at or 771-474-5377.

Sincerely yours,

Michael S. Regan

  1. See 80 FR 12294 (March 6, 2015); 83 FR 63010 (December 6, 2018); and Final Guidance on the Preparation of Clean Air Act Section 179B Demonstrations for Nonattainment Areas Affected by International Transport of Emissions, available at
  2. 89 FR 14760 (February 29, 2024); “Request From States for Removal of Gasoline Volatility Waiver,” available at
  3. See 61 FR 14363.