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USEPA Revises National Ambient Air Quality Standard for Ozone

On October 1, 2015, the United States Environmental Protection Agency (USEPA) strengthened the National Ambient Air Quality Standard (NAAQS) for ground-level ozone by lowering the standard from 75 parts per billion (ppb) to 70 ppb. Citing extensive scientific evidence, particularly in relation to childhood asthma concerns, USEPA had requested public input on an ozone NAAQS as low as 60 ppb, but settled on a more reasonable, and defensible, standard of 70 ppb.


USEPA issued the first national air quality standards for ozone in 1971. The agency has revised the standards three times – in 1979, 1997 and 2008 – and has an obligation to review all NAAQS every five years to ensure the standards protect public health and welfare.

Scientific evidence indicates that exposure to ground-level ozone can exacerbate existing breathing and pulmonary diseases such as asthma and COPD (chronic obstructive pulmonary disease). Evidence also indicates that long-term exposures to ozone may be one of the likely causes of asthma development. An estimated 23 million people have asthma in the U.S., including an estimated 6.1 million children. USEPA believes that the new ozone NAAQS provides an adequate margin of safety to protect these at-risk groups and that the estimated annual cost of the rule ($1.4 billion) is sufficiently outweighed by the public benefits, which are expected to range from $2.9-$5.9 billion annually (by 2025).

The debate leading up to USEPA’s issuance of the revised ozone NAAQS was robust. Many manufacturing groups (e.g., National Association of Manufacturers) and trade organizations [e.g., American Federation of Labor and Congress of Industrial Organizations (AFL-CIO)] lobbied the Obama Administration to leave the standard alone or adjust it to the high end of the range considered. On the other hand, environmental advocacy and public interest groups (e.g., Clean Air Watch) requested that the Administration consider reducing the standard to the lowest possible level. The debate is unlikely to subside anytime soon – within a month of promulgating the final rule, USEPA was sued by at least five states and an individual corporation – with Republican lawmakers threatening to prepare legislation to prevent USEPA from implementing the new standards.

Highlights of the new Ozone NAAQS

Under the Clean Air Act, USEPA must designate areas as meeting the standards (attainment areas), not meeting them (nonattainment areas), or where there is not enough information available with which to make a designation (unclassifiable). States with nonattainment areas must develop air emission inventories and implement a pre-construction permitting program design to provide additional air quality safeguards for those areas.

Furthermore, states with nonattainment areas classified as “moderate” or higher (indicating a more severe level of nonattainment status) must develop State Implementation Plans (SIPs) showing how the areas will meet the new standards. These states must also adopt reasonably available control technology (RACT) standards for certain types of emission sources in the nonattainment areas of their state.

One interesting aspect of the new rule is that USEPA issued a “grandfathering” provision for certain Prevention of Significant Deterioration (PSD) pre-construction permitting requirements so that compliance with the new ozone standards will not delay final processing of pending permit applications. This grandfathering provision applied only to projects for which the permitting agency has formally determined the application to be complete as of October 1, 2015, or the public notice of a draft permit or preliminary determination has been published prior to December 25, 2015 (the effective date of the revised ozone standards). The grandfathering provisions do not apply to nonattainment New Source Review permit applications, since such projects are subject to different requirements.

Anticipated Impact on Industry

USEPA estimates that the majority of U.S. counties will meet these new standards by 2025 as a result of federal and state rules that are already in place. Examples of rules that are already reducing compounds, such as volatile organic compounds (VOC) and nitrogen oxides (NOx), that are precursors to ground-level ozone formation include:

  • Regional haze regulations
  • Mercury and air toxic standards
  • Tier 3 vehicle emission and fuel standards
  • Light-duty vehicle Tier 2 rule
  • Reciprocating internal combustion engines NESHAP
  • Industrial boiler MACT standards

Thus, if USEPA’s projections are correct, there may be limited impact on industry, since a large number of new rules will not need to be implemented to help states and local counties/air districts attain the new NAAQS. Nevertheless, over the next year, USEPA anticipates proposing rules and guidance to help states implement the revised standards.


As required by the Clean Air Act, USEPA anticipates making attainment/nonattainment designations for the revised standards by late 2017. Those designations likely will be based on 2014-2016 air quality data. Nonattainment areas will have until 2020 to late 2037 to meet the health standard, with attainment dates varying based on baseline ozone concentrations, with more time being given to areas with higher ozone levels.

Matt Traister
(315) 569-7882