Current Status
EPA is currently reviewing the science underlying the 2020 Ozone NAAQS with the aid of the Clean Air Science Advisory Committee (CASAC), an independent expert committee that assists EPA in reviewing the NAAQS. EPA is considering whether to retain the current ozone NAAQS or implement more stringent standards.
Why it Matters
Ground-level ozone is emitted from vehicles, power plants, and other industrial sources. It reacts with sunlight and other pollutants to form smog, which can aggravate asthma and cause other respiratory issues, especially in children who are playing outdoors and people with existing lung problems.
The Clean Air Act (CAA) requires EPA to review NAAQS every five years to ensure their adequacy. EPA sets primary and secondary standards for ozone.
Key Resources
Timeline
Feb. 2, 2024 The DC Circuit granted EPA’s unopposed motion for voluntary remand without vacatur. In its motion, EPA had said that the agency would institute a new review of the Ozone NAAQS. New York et al. v. EPA, No. 21-1028 (D.C. Cir. Jan. 19, 2021).
Oct. 12, 2023 The DC Circuit granted petitioners’ motion to lift abeyance and return the consolidated cases to the court’s active docket. New York et al. v. EPA, No. 21-1028 (D.C. Cir. Jan. 19, 2021).
Oct. 6, 2023 Petitioners filed a motion to lift abeyance with the D.C. Circuit to restart their case challenging EPA’s 2020 decision to not revise the ozone NAAQS, arguing that EPA “informed the parties and the Court that it will take no action regarding the 2020 ozone decision at this time.” New York et al. v. EPA, No. 21-1028 (D.C. Cir. Jan. 19, 2021).
Aug. 25, 2023 EPA issued a public notice soliciting scientific information for consideration in developing the Integrated Science Assessment (ISA) for its review of the primary and secondary ozone NAAQS. Specifically, EPA is sought peer-reviewed scientific literature and research studies that have been published since EPA last collected information for the most recent ISA in 2020.
Aug. 18, 2023 EPA notified CASAC that it will initiate a new statutory review of the ozone NAAQS and the underlying air-quality criteria.
July 17, 2023 Environmental groups challenged EPA’s decision to accept an “exceptional event” that allowed Detroit to maintain its attainment designation. Sierra Club v. EPA, Docket No. 23-3581 (6th Cir. July 17, 2023).
June 9, 2023 CASAC sent a letter and final report to EPA, reviewing EPA’s Policy Assessment (PA) in which a majority of CASAC members recommended EPA consider a revised NAAQS range of 55 to 60 ppb. CASAC found that EPA did not fully utilize the “wealth of information” the agency had in developing the PA, instead relying heavily on controlled human exposure (CHE) and quantitative risk and exposure assessment (REA) data, and not adequate incorporating epidemiological and animal studies, or information about impacts on children, at-risk populations, and outdoor workers.
May 2, 2023 CASAC released a draft report reviewing EPA’s Policy Assessment (PA) for the reconsideration of the ozone NAAQS. It expressed concern that EPA’s proposed approach of retaining the 70 ppb standard “substantially underestimate[s] public health risk.” A majority of CASAC members recommend a stricter ozone NAAQS range of 55 to 60 ppb. CASAC also recommended that EPA include epidemiological data and data on the impact of ozone on children and outdoor workers to fully capture the health risks posed to at-risk populations before finalizing the revised ozone NAAQS.
Mar. 1, 2023 EPA issued a second draft Policy Assessment (PA) for Reconsideration of the 2015 Ozone NAAQS, reassessing the scientific evidence presented in the 2020 ISA, related air quality, exposure, and risk analyses, and the 2020 PA. EPA staff recommended the agency leaves the 2015 standards unchanged from 70 ppb, finding that the current standards provide “adequa[te]” protection from ozone exposure. EPA’s first periodic review of 2015 Ozone NAAQS in Dec. 2020 also retained the 2015 Ozone NAAQS at 70 ppb.
Jan. 3, 2023 EPA notified CASAC that the agency is rewriting a draft policy assessment (PA), as a preliminary step for the agency’s reconsideration of the 2020 Ozone NAAQS. This decision wasbased on CASAC’s earlier recommendation that the scientific evidence in the 2020 ISA provides adequate basis to review the 2020 Ozone standards, which warranted EPA’s re-writing of the current PA that had concluded EPA should retain the 2020 Ozone standards.
Apr. 28, 2022 EPA Staff released its draft policy assessment (PA) finding that it is appropriate to retain the primary and secondary ozone NAAQS set in 2015 and retained in 2020 by the Trump administration. The draft PA acknowledges that it “draws heavily on information presented in the 2020 PA.”Nov. 22, 2022 CASAC submitted a letter sent to EPA Administrator Regan formally approving the 2020 ISA conducted by the Trump EPA. CASAC also found that the evidence in 2020 ISA supports setting a more robust secondary standard for Ozone.
Oct. 28, 2021 EPA announced it will reconsider the Trump EPA’s decision not to strengthen the ground-level ozone NAAQS.
Feb. 26, 2021 The D.C. Circuit ordered the cases challenging the Trump administration’s ozone decision in abeyance. American Academy of Pediatrics, et al v. EPA, No. 21-01060 (D.C. Cir.).
Jan. 20, 2021 President Biden’s Executive Order revoked a Trump-era memo that required EPA to reevaluate its process for setting the NAAQS and directed EPA to review the ozone NAAQS rule.
Jan./ Feb., 2021 A coalition of states, public health and environmental groups challenged EPA’s decision not to update the ground-level ozone NAAQS. American Academy of Pediatrics, et al v. EPA, No. 21-01060 (D.C. Cir.).
July 13, 2020 EPA proposed to retain the ozone NAAQS. Dec. 31, 2020 EPA finalized rule retaining the current NAAQS for ozone, finding “that the current primary standard is requisite to protect public health, including the health of at-risk populations, with an adequate margin of safety, and should be retained, without revision.”
May 31, 2020 EPA published the final Policy Assessment for ozone, affirming that the most recent scientific evidence continues to support retaining the current ozone NAAQS. The Policy Assessment projected that EPA will publish a proposed decision on retaining or changing the ozone NAAQS in mid-2020.
April 1, 2020 Administrator Wheeler sent a letter to CASAC Chair Tony Cox stating that EPA intended to maintain its 2020 deadline for the ozone NAAQS. Wheeler acknowledged that this deadline meant many of CASAC’s comments on the Integrated Science Assessment that are “more substantial or cross-cutting” will not be addressed in this review cycle.
Feb. 12, 2020 CASAC agreed on a final report to Administrator Wheeler recommending no change to the existing ground-level ozone standard. The report also urged EPA to restore the independent ozone review panel and in-person meetings between CASAC and members of the panel.
Dec. 2, 2019 18 former members of the CASAC Ozone Review Panel sent a letter to EPA stating that the changes EPA has made to the NAAQS review process “are collectively harmful to the quality, credibility, and integrity of EPA’s scientific review process and to CASAC as an advisory body.” The letter also stated that “[t]he NAAQS review for ozone should be suspended until these deficiencies are corrected.”
Oct. 31, 2019 EPA released the draft Policy Assessment for the Ozone NAAQS before CASAC reviewed it. The Policy Assessment found that the newly available evidence continued to support the current ozone NAAQS. The Policy Assessment was also slated for discussion at the December 2019 CASAC meeting.
Sep. 26, 2019 EPA published the draft Integrated Science Assessment for Ozone, in advance of the December 2019 CASAC meeting.
Aug. 22, 2019 EPA published the Integrated Review Plan for the Review of the Ozone NAAQS, which included a timeline projecting that EPA will finalize the Ozone NAAQS in “Winter 2020/2021.” Aug. 23, 2019 The DC Circuit upheld the 2015 primary ozone NAAQS in Murray Energy Corp. v. EPA, No. 15-1385. While the court denied most challenges, it remand the secondary standards to the agency for reconsideration, and vacates a provision that grandfathered in permit applications submitted by industry before the 2015 revision that would not comply with the newly revised NAAQS.
Oct. 10, 2018 EPA issued a press release tasking CASAC with reviewing the ozone NAAQS, notably eliminating the role of independent review panels that were historically convened to assist CASAC. Dec. 10, 2018 Three CASAC members urged EPA to reconvene the Ozone Review Panel in their comments on the draft Integrated Review Plan for ozone NAAQS.
Aug. 1, 2018 EPA filed a status report with the DC Circuit indicating that “the appropriate EPA officials have reviewed the 2015 [Ozone NAAQS] Rule and have determined that at this time, EPA does not intend to revisit the 2015 Rule.” Murray Energy Corp. v. EPA, No. 15-1385 (D.C. Cir.).
July 3, 2018 The Court of Appeals for the District of Columbia returned the Murray Energy Corp. v. EPA litigation to its active docket. Murray Energy Corp. v. EPA, No. 15-1385 (D.C. Cir.).
June 26, 2018 EPA announced the beginning of its next review of the ozone NAAQS by issuing a call for information to assist EPA in developing the review plan and science assessment.
Aug. 2, 2017 EPA announced it will walk back the national delay and proceed as originally scheduled.
July/Aug. 2017 Environmental groups and states challenged EPA’s delay of the ozone rule. American Lung Association et al v. EPA, Case No. 17-1172;1185 (D.C. Cir.).
June 28, 2017 EPA published notice that it will delay implementation of the ozone standards by one year to October 1, 2018.
April 11, 2017 The court removed the argument from its calendar and ordered EPA to provide status reports every 90 days.
April 7, 2017 EPA requested the court to delay the oral argument scheduled for April 19, 2017. EPA stated it “intends to closely review the 2015 Rule, and the prior positions taken by the Agency with respect to the 2015 Rule may not necessarily reflect its ultimate conclusions after that review is complete.”
Sep. 14, 2016 Murray Energy sued EPA challenging the new standards. Murray Energy Corp. v. EPA, Case No. 15-1385 (D.C. Cir.).
Oct. 25, 2015 EPA concluded its review of the ozone NAAQS and determined that the existing standards inadequately protect public health and welfare. EPA tightens the health-based and welfare-based standards to 0.070 parts per million.