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News Releases from HeadquartersAir and Radiation (OAR)

Ozone Pollution Continues to Decline Under President Trump, EPA Proposes to Retain Existing NAAQS for Ozone

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WASHINGTON (July 13, 2020) — Today, the U.S. Environmental Protection Agency (EPA) is announcing its proposal to retain, without changes, the existing, more stringent 2015 National Ambient Air Quality Standards (NAAQS) for ozone. This proposal comes after careful review and consideration of the most current available scientific evidence and risk and exposure information, and with consultation of the Agency’s independent science advisors. 

“Under President Trump, the U.S. has made significant progress in reducing ozone concentrations across the nation,” said EPA Administrator Andrew Wheeler. “Based on a review of the scientific literature and recommendation from our independent science advisors, we are proposing to retain existing ozone standards which will ensure the continued protection of both public health and the environment.”

From 2017 to 2019, ozone concentrations fell 4 percent. Since the beginning of the Trump Administration, EPA has also re-designated 13 nonattainment areas for the 2008 8-hour ozone standards to attainment meaning these communities are now breathing cleaner air. 

With this action, EPA is following the principles established in the earliest days of the Trump administration to streamline the NAAQS review process and to fulfill the statutory responsibility to complete the NAAQS review within a 5-year timeframe. EPA is on track to finalize the 2015 ozone NAAQS review in 2020 – marking only the second time the agency has met the 5-year timeframe in its history. This is a needed departure from the previous administration’s failure to meet statutory deadlines, often taking twice as long to promulgate updated standards.

While consulting the Clean Air Science Advisory Committee (CASAC) on the draft Policy Assessment, which included current scientific evidence and quantitative air quality, exposure and risk analyses, a majority of CASAC members recommending the agency retain the primary standard, and reaching consensus to recommend EPA retain the secondary standard.

As a result of Clean Air Act programs and efforts by state, local, and tribal governments, from 1990-2019, U.S. emissions of nitrogen oxides and volatile organic compounds – air pollutants that contribute to the formation of ground-level ozone – have dropped by 65 percent and 47 percent respectively. During that same time, national average ozone concentrations have dropped 25 percent.

EPA will accept comment on this proposed decision for 45 days after it is published in the Federal Register. For more information, see: . 


The Clean Air Act requires EPA to set NAAQS for “criteria pollutants.” Currently, ozone (and related photochemical oxidants) and five other major pollutants are listed as criteria pollutants. The law requires EPA to periodically review the relevant scientific information and the standards and revise them, if appropriate, to ensure that the standards provide the requisite protection for public health and welfare.

In the prior review of the ozone standards, which was completed in 2015, EPA increased the stringency of the levels of the ozone standards to 70 parts per billion (ppb), from the 2008 standard of 75 ppb.

As stated in the NAAQS review guidance, EPA is focused on reviewing the NAAQS within the Clean Air Act 5-year time frame because of the potentially significant impacts of a NAAQS revision on economic activity, state agency planning resources, public health, and the environment, it is important that these reviews are completed in a timely, efficient, and transparent manner.