SUPPLEMENTARY INFORMATION:

I. Information About the Project

Section 108(a) of the Clean Air Act (CAA) directs the Administrator to identify and to list certain air pollutants and then to issue “air quality criteria” for those pollutants. These air quality criteria are to “accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare which may be expected from the presence of such pollutant in the ambient air. . . .” Under section 109 of the CAA, EPA is then to establish National Ambient Air Quality Standards (NAAQS) for each pollutant for which EPA has issued criteria. Section 109(d)(1) of the CAA additionally requires periodic review and, if appropriate, revision of existing air quality criteria to reflect advances in scientific knowledge on the effects of the pollutant on public health and welfare. EPA is also to periodically review and, if appropriate, revise the NAAQS, based on the revised air quality criteria.

Photochemical oxidants, including ozone, are one of six “criteria” pollutants for which EPA has established NAAQS, and ozone is the current indicator for that NAAQS. In its periodic review of the air quality criteria for these pollutants, EPA reviews the currently available science and prepares an Integrated Science Assessment (ISA). The evidence assessed and conclusions presented in the ISA directly inform the technical and policy assessments. Collectively, the ISA and any technical and policy assessments developed from the scientific and technical bases for the Administrator's decisions on the adequacy of existing NAAQS and the appropriateness of possible alternative standards.

On August 25, 2023, EPA released the Call for Information on the Integrated Science Assessment for Ozone and Related Photochemical Oxidants to announce the development of the Ozone ISA (88 FR 58264). The Notice of Workshop also seeks information from the public regarding the design and scope of the review of the air quality criteria to ensure that this review addresses key policy-relevant issues and considers the new science relevant to informing our understanding of these issues. The Clean Air Scientific Advisory Committee (CASAC), part of EPA's Science Advisory Board (SAB) whose review and advisory functions are mandated by section 109(d)(2) of the Clean Air Act, is charged with independent scientific review of the air quality criteria among other responsibilities. In conjunction with the ( printed page 31201) CASAC review, the public will have an opportunity to review and comment on the draft ozone ISA. As the process proceeds, in conjunction with CASAC review, the public will have opportunities to review and comment on drafts of other technical and policy assessments that are developed. These opportunities will also be announced in the Federal Register .

As part of this review of the ozone NAAQS, EPA intends to sponsor a four-day workshop from May 13 through May 16, 2024, to provide the opportunity for internal and external experts to highlight significant new and emerging research on ozone and related photochemical oxidants. Experts will be asked to discuss how new evidence can best be used to build upon the analyses and scientific evidence that supported decisions made in the last review of the ozone NAAQS and to make recommendations to the Agency regarding the design and scope of the review for the primary (health-based) and secondary (welfare-based) ozone standards to ensure that it addresses key policy-relevant issues and considers the new and emerging science that is relevant to informing EPA's understanding of these issues. EPA intends that workshop discussions will build upon four prior publications by the Agency:

1. Review of the Ozone National Ambient Air Quality Standards: Final Decision (85 FR 87256, December 31, 2020). The preamble to the final rule included detailed discussions of policy-relevant issues central to the last review.

2. Integrated Science Assessment for Ozone and Related Photochemical Oxidants—Final Report. (EPA/600/R-20/012, April 2020). The 2020 Ozone ISA, completed by CPHEA, included consideration of studies published through January 1, 2018.

3. The final Policy Assessment for the Review of the Ozone National Ambient Air Quality Standards (EPA-452/R-20-001, May 2020). This document presents an evaluation, for consideration by the EPA Administrator, of the policy implications of the currently available scientific information, assessed in the ISA, any quantitative air quality, exposure, or risk analyses based on the ISA findings, and related limitations and uncertainties.

4. The draft document titled, Policy Assessment for the Reconsideration of the Ozone National Ambient Air Quality Standards, External Review Draft Version 2 (EPA-452/P-23-002, March 2023). This draft document was prepared as a part of the reconsideration of the 2020 final decision on the ozone NAAQS, which has been incorporated into this review.

Workshop participants are encouraged to review these documents thoroughly before the meeting, as they provide important background information on the scientific findings and analytical approaches considered in the previous review, as well as insights into the key policy-relevant questions from that review. Participants may also want to review related documents including:

1. Technical memos considered by the CASAC Ozone Panel as part of the reconsideration of the 2020 decision (available on the CASAC website under “meeting materials” at https://casac.epa.gov/​ords/​sab/​r/​sab_​apex/​casac/​meeting?​p19_​id=​976&​clear=​19&​session=​15138357514835).

2. Letter from Elizabeth A. Sheppard, Chair, Clean Air Scientific Advisory Committee, to Administrator Michael S. Regan. Re: CASAC Review of the EPA's Integrated Science Assessment (ISA) for Ozone and Related Photochemical Oxidants (Final Report—April 2020). November 22, 2022. EPA-CASAC-23-001. Available at: https://casac.epa.gov/​ords/​sab/​f?​p=​105:18:8476900499267:::RP,18:P18_​ID:2614.

3. Letter from Elizabeth A. Sheppard, Chair, Clean Air Scientific Advisory Committee, to Administrator Michael S. Regan. Re: CASAC Review of the EPA's Policy Assessment (PA) for the Reconsideration of the Ozone National Ambient Air Quality Standards (External Review Draft Version 2) (June 9, 2023) (EPA-CASAC-23-002). Available at https://casac.epa.gov/​ords/​sab/​f?​p=​113:18:7093179574667:::RP,18:P18_​ID:2636#meeting.

Following the workshop, EPA will develop a workshop proceedings document and a three-volume Integrated Review Plan (IRP) for the review of the ozone NAAQS. Volume 1 will provide background on the ozone NAAQS. Volume 2 is the planning document for the review and the ISA, and will outline the schedule, process, and approaches for evaluating the relevant scientific information and addressing the key policy-relevant issues to be considered in this review. Lastly, Volume 3 is the planning document for technical air quality, exposure, and risk analyses. CASAC will be asked to consult with the Agency on Volumes 2 and 3, and the public will also have the opportunity to comment. The IRP, with input received from the CASAC and the public, will provide the framework to guide the review and development of the draft ISA and policy assessments.