I. Background

A. Executive Summary This section summarizes information about the purpose of this regulatory action in section 1, the major provisions of this proposal in section 2, and provisions related to implementation in section 3

. 1. Purpose of This Regulatory Action Sections 108 and 109 of the Clean Air Act (CAA) govern the establishment, review, and revision, as appropriate, of the NAAQS to protect public health and welfare. The CAA requires the EPA to periodic ally review the air quality criter ia

— the science upon which the standards are based

— and the standards themselves. This rulemaking is being conducted pursuant to these statutory r equirements. The schedule for completing this review is established by a federal court order , which requires tha t the EPA sign a proposal by December 1, 2014, and make a final determination by October 1, 2015

. The EPA completed its most recent review of the O 3 NAAQS in 2008

. As a result of that review, EPA took four principal actions: (1) revised the level of the 8

- hour primary O 3 standard to 0.075 parts per million (ppm); (2) expressed the standard to three decimal places; (3) revised the 8

- hour secondary O 3 standard by making it identical to the revised primary standard; and (4) made conforming changes to the AQI for O 3 . In subsequent litigation , the U.S. Court of Appeals for the D istrict of Columbia Circuit upheld the EPA’s 2008 primary O 3 standard, but remanded the 2008 secondary standard

. ( State of Mississippi v. EPA , 744 F. 3d 1334

. ) With respect to the primary standard, the court held that the EPA reasonably determined that the existing primary standard , set in 1997, did not protect public health with an adequate margin of safety and required revision. In uph o ld ing the EPA’srevised primary standard , the court dismiss ed arguments that the EPA should have adopted a

more stringent standard

. The court remanded the secondary standard to the EPA after rejecting the EPA’s explanation for setting the secondary standard identical to the revised 8

- hour primary standard. The court held that because the EPA had failed to identify a level of air quality requisite to protect public welfare, the EPA’s comparison between the primary and secondary standards for determining if requisite protection for public welfare was afforded by the primary standard did not comply with the CAA. This proposal reflects the Administrator’s proposed conclusions based on a review of the
O 3 NAAQS that began in September 2008. In conducting this review, the EPA has carefully evaluated the currently available scientific literature on the health and welfare effects of ozone, focusing particularly on the new literature available since the conclusion of the previous review in 2008. In addition, the EPA has also addressed the remand by the U.S. Court of Appeals (D.C. Circuit) of the Agency’s 2008 decision on the secondary standard. Between 2008 and 2014, the EPA prepared draft and final versions of the Integrated Science Assessment, t he Health and Welfare Risk and Exposure Assessments, and the Policy Assessment. Multiple drafts of these documents were available for public review and comment, and as required by the Clean Air Act,
were peer - reviewed by the Clean Air Scientific Advisory C ommittee (CASAC) , an independent scientific advisory committee established by the C AA and charged with providing advice to the Administrator

. The f

inal documents reflect the EPA staff’s consideration of the comments and recommendations made by CASAC and th e public on draft versions of these documents

. 2. Summary of Major Provisions The EPA is proposing that the current primary O 3 standard of 0.075 ppm is not adequate to protect public health, and that it should be revised to provide increased public healthprotection. Specifically, the EPA is proposing to retain the indicator (ozone), averaging time (8

-

hour) and form (annual fourth

- highest daily maximum, averaged over 3 years) of the existing primary O 3 standard and is proposing to revise the level of that standard to within the range of
0.0 65 ppm to 0.0 70 ppm. The EPA is proposing this revision to increase public health protection , including for “at

- risk” populations such as children , older adults, and people with asthma or other lung diseases, against an array of O 3 - related adverse health effects . For short

- term O 3 exposures, these effects include decreased lung function, increase d respiratory symptoms and pulmonary inflammation, effects that result in serious indicators of respiratory morbidity such as

em ergency department visits and hospital admissi ons, and all

- cause ( total nonaccidental ) mortality . For long

- term O 3 exposures, these health effects include a variety of respiratory morbidity effects and respiratory mortality. Recognizing that the CASAC reco mmended a range of levels from 0.060 ppm to 0.070 ppm, and that levels as low as 0.060 ppm could potentially be supported , the Administrator solicits comment on alternative standard levels below 0.0 65 pp m , and as low as 0.0 60 pp m . However, the Administrato r notes that setting a standard below 0.065 ppm, down to 0.060 ppm, would place very little weight on the uncertainties in the health effects evidence and exposure/risk information , which she proposes would be inappropriate at this time. Given alternative views of the currently available evidence and information expressed by some
commenters, t he EPA is taking comment on the Administrator’s proposed decision to revise the current primary O 3 standard and the option of retaining that standard. In addition to p roposing changes to the level of the standard, the EPA is proposing conforming changes to the A ir Quality Index (A QI ) by proposing to set an AQI value of 100 equal to the level of the 8

- hour primary O 3 standard, and proposing proportional changes to the AQI values of 50, 150, 200 and 300.The EPA also proposes to revise the secondary standard to provide increased protection

against vegetation

- related effects on public welfare. As an initial matter, the Administrator
proposes to conclude that air quality i n terms of a three

- year average seasonal W126 index value , based on the three consecutive month period within the O 3 season with the maximum index value, with daily exposures cumulated for the 12

- hour period from 8:00 am to 8:00 pm , within the range from 1 3 ppm

- hrs to 17 ppm

- hrs would provide the requisite protection against known or anticipated adverse effects to the public welfare. The EPA solicits comment on this proposed conclusion. In considering how t o achieve that level of air quality, the Administ rator recognizes that air quality data analyses suggest that air quality in terms of three

- year average W126 index values of a range at or below 13 to 17 ppm

- hrs would be provided by a secondary standard level within the range proposed for the primary stan dard of 0.065 to 0.070 ppm , and that to the extent areas need to take action to attain a standard in the range of 0.0 65 to 0.0 70 pp m , those actions would also improve air quality as measured by the W126 metric. Thus , the Administrator proposes to revise th e level of the current secondary standard to within the same range proposed for the primary O 3 standard of 0.065 to 0.070 ppm

. The EPA solicits comments on this proposed revision of the secondary standard. The EPA also solicits comments on the alternative approach of revising the secondary standard to a W126

- based form, averaged over three years, with a level within the range of 1 3
ppm - hrs to 1 7 ppm - hrs. The EPA additionally solicits comments on such a distinct secondary standard with a level within the range extending below 13 ppm

- hrs down to 7 ppm

- hrs. T he EPA is also taking comment on the Administrator’s proposed decision to revise the current secondary standard and the option of retaining that stan dard

. 3. Provisions Related to ImplementationAs directed by the C AA , reducing pollution to meet national air quality standards always

has been a shared task, one involving the federal government, states, tribes and local air agencies. This partnership has proved effective since the EPA first issued O 3 standards more than three decades ago, and is evidenced by the significantly lower O 3 levels throughout the country. To provide a foundation that helps air agencies build successful strategies for attaining n ew O 3 standards , t he EPA will continue to move forward with federal regulatory programs, such as the proposed Clean Power Plan and the final Tier 3 motor vehicle emissions standards. T o facilitate the development of C AA

- compliant implementation plans and s trategies to attain new standards , t he EPA intends to issue timely and appropriate implementation guidance and, where appropriate and consistent with the law , new rulemaking s to streamline regulatory burdens and provide flexibility in implementation. In ad dition, given the regional nature of O 3 air pollution, the EPA will continue to work with states to address inte r state transport of O 3 and O 3 precursors . This notice contains several proposed provisions related to implementation of the proposed standards

. These proposed provisions are intended to ensure future implementation actions are not overly burdensome and are clearly essential for achieving and maintaining clean air. In addition to revisions to the primary and secondary NAAQS, t he EPA is proposing to make corresponding revisions in data handling conventions for O 3 ; to revise regulations for the
P revention of S ignificant Deterioration (PSD) permitting program to add a provision grandfathering certain pending permits from certain requirements with respe ct to the proposed revisions to the O 3 NAAQS; and to convey schedules and information related to implementing any revised standards

. With respect to monitoring, t he EPA is proposing changes to the O 3 monitoring seasons, the F ederal R eference M ethod (FRM) f or monitoring O 3 in the ambient air,F ederal E quivalent M ethod (FEM) procedures for testing, and the P hotochemical A ssessment

M onitoring S tations (PAMS) network.
I n conjunction with proposing exceptional event schedules related to implementing any revised O 3 standards, the EPA is also proposing to extend the new schedule approach to other future revised NAAQS and to remove obsolete regulatory language associated with expired exceptional event deadlines for historical standards for both O 3 and other NAAQS p ollutants. The EPA is also proposing to make minor changes to the procedures and time periods for evaluating potential FRMs and equivalent methods , including making the requirements for nitrogen dioxide consistent with the requirements for O 3 , and removing an obsolete requirement for the annual submission of documentation by manufacturers of certain particulate matter monitors.