EPA Proposes Stricter Limits on Ozone Levels

Environmental Update

Date: December 22, 2014

The Environmental Protection Agency recently issued a proposed rule under Section 109 of the Clean Air Act (CAA) that would significantly lower the National Ambient Air Quality Standards (NAAQS) for ozone (Proposal). The Proposal would reduce the primary and secondary ozone NAAQS, which were set at 75 parts per billion (ppb) in 2008, to between 65 and 70 ppb. EPA issued the Proposal in response to a court-imposed deadline stemming from litigation concerning its failure to review the 2008 ozone standards within five years of their establishment, as required by Section 109. If the Proposal is implemented, the agency will likely find itself embroiled in litigation once again, as many industry groups and states have criticized the revised standards as imposing billions of dollars in costs without having any meaningful impact on air quality.

NAAQS Program

Section 109 of the CAA requires EPA to establish primary and secondary NAAQS for pollutants considered harmful to public health and the environment. NAAQS have been set for six pollutants: particulate matter, nitrogen dioxides, carbon monoxide, sulfur dioxide, lead and ozone. Primary standards must protect public health “with an adequate margin of safety,” including the health of sensitive populations such as asthmatics, children and the elderly. Secondary standards must protect the public welfare, including protection against visibility impairment and damage to animals, crops, vegetation and buildings. Section 109 requires EPA to review and, if appropriate, revise the NAAQS every five years.

Once NAAQS have been set, EPA designates areas meeting the standards as “attainment” and those not meeting the standards as “nonattainment.” States then have three years to prepare State Implementation Plans (SIPs) that outline how emissions will be reduced in nonattainment areas to achieve compliance with the standards. Attainment of primary standards can stretch over a three-year to 20-year period, depending on the severity of the area’s pollution, while compliance with secondary standards must be achieved as soon as practicable.

Rulemaking Background

EPA’s issuance of revised ozone standards has been in the works for several years. Shortly after the current primary and secondary standards of 75 ppb were established in 2008, EPA announced that it was reconsidering its decision to ensure that the standards were clearly grounded in science and protective of public health and the environment. In 2010 the agency proposed a revised primary standard of between 60 and 70 ppb and a revised secondary standard in the range of 7 to 15 parts per million-hours.1 After a year and a half of public comment and review, EPA sent what it considered a final set of standards to the Office of Management and Budget for interagency review. The process was short-circuited, however, after President Obama announced that the promulgation of final ozone standards would be delayed until after EPA completed its five-year review of the 2008 standards, which was supposed to be completed by March 2013. When EPA failed to meet that deadline, the Sierra Club and others filed suit. The court subsequently ordered the agency to issue proposed standards by December 1, 2014 and final standards by October 1, 2015.

Revised Standards & Other Key Changes

As mentioned above, EPA is proposing a primary ozone standard in the range of 65 to 70 ppb. The agency is seeking comment, however, on setting the standard as low as 60 ppb in light of the Clean Air Scientific Advisory Committee’s recommendation of a range between 60 and 70 ppb. EPA is likewise proposing a secondary ozone standard between 65 and 70 ppb. The agency will also accept comments on defining the secondary ozone standard in terms of the W126 index, as well as retaining the existing standard of 75 ppb.

In addition to the revised standards, EPA is proposing an extension of the ozone monitoring season for 33 states. Under the Proposal, the monitoring season would be extended by one month for 24 of the 33 states, with longer extensions in the remaining nine states, such as Utah, where ozone monitoring would be required for an additional seven months.

EPA is also proposing updates to the Air Quality Index (AQI) for ozone, which is EPA’s color-coded tool for telling the public how clean or polluted the air is and recommending steps people can take to reduce their daily exposure to pollution. EPA is proposing to lower the breakpoints for each AQI category, based on the level of the proposed primary standard, as well as information from health studies examined in connection with the review of the standards.

Future Implications

If implemented, the Proposal will have substantial and far-reaching impacts. According to 2011 – 2013 ozone monitoring data, 358 counties across the country would violate a standard of 70 ppb. An additional 200 counties would violate a standard of 65 ppb. Designating large swaths of the country as nonattainment areas will necessarily drive up compliance costs as states implement strict measures to achieve the revised standards, such as imposing more onerous pre-construction permitting requirements on industry (including imposition of “Lowest Achievable Emissions Rate”-based control technology and emissions offsets). Indeed, by EPA’s own estimation, compliance with a 70 ppb standard would cost $3.9 billion annually, beginning in 2025, while compliance with a 65 ppb standard would cost a staggering $15 billion annually.

Next Steps

EPA will accept comments on the Proposal until March 17, 2015. The agency is required by court order to issue a final rule by October 1, 2015. Final area designations will be made by October 1, 2017. States will then have three years to prepare and submit SIPs. Deadlines for complying with the primary standards will be from 2020 to 2037, depending on the severity of an area’s ozone problem, and compliance with the secondary standards will be determined by the agency and the states through the implementation planning process.

The full text of the proposed rule can be found on EPA’s website or in the December 17, 2014 Federal Register at 79 Fed. Reg. 75234.


For more information, please contact:

Wray Blattner

Andrew L. Kolesar

Erin M. Minor

or any member of Thompson Hine’s Environmental practice group.

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1The secondary standard is expressed in terms of the W126 index, which is designed to account for the cumulative effects of repeated ozone exposures on sensitive vegetation during the three months of the year when ozone concentrations are highest. See EPA, “January 2010 Proposal to Revise the National Ambient Air Quality Standards for Ground-level Ozone, General Overview,” at 11-12.