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EPA Finalizes 70 ppb Ozone NAAQS
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EPA Finalizes 70 ppb Ozone NAAQS  


On October 1, the Obama administration set a more stringent national ambient air quality standard (NAAQS) for ground-level ozone when,  as expected, EPA finalized a new standard of 70 parts per billion, the upper end of the range that the agency proposed last November.  The new standard represents a drop from the existing limit of 75 ppb, which was set in 2008 during the George W. Bush administration.  The final rule was required under a judicial deadline after the agency missed a Clean Air Act-mandated deadline to review its 2008 ozone standard of 75 ppb in 2013.


EPA determined, through a review of public health science and more than 430,000 comments, that the 2008 standard was no longer adequate to protect public health as the Clean Air Act required.  EPA's Clean Air Scientific Advisory Committee (CASAC) endorsed tightening the limit to within the range of 60 ppb-70 ppb in order to protect public health, but the agency in November proposed a narrower range of 65 ppb-70 ppb.  By law, the agency cannot consider costs in setting the level of NAAQS and must do so based solely on scientific data about a criteria pollutant's adverse impacts.  The primary health-based standard must under the air law be set at a level requisite to protect public health with an adequate margin of safety. 


EPA will designate areas that are in noncompliance with the standard in 2017 based on 2014, 2015 and 2016 air quality data.  Under the law, states will be required to develop and put in place pollution control plans for areas found to contain ozone concentrations above the limit.  EPA said most areas that monitor their air quality will meet the new standard by 2025 because of actions already taking place to cut pollution from cars and factories.  The agency said the standard will cost $1.4 billion annually but achieve benefits in the form of health care savings of up to $5.9 billion in 2025.  The analysis excludes California, which is expected to take longer to come into compliance.  EPA estimates that 213 counties outside California would initially violate the standard based on recent air monitoring, and based on modeling, the agency said 14 counties outside of California would be unable to achieve the 70 ppb limit by 2025, including areas around the New York City metropolitan area, Pittsburgh and Houston.


While most of EPA's focus was on the benefits associated with the primary, health-based standard, the agency's final rule also revised the secondary, welfare-based ozone standard to 70 ppb.  The secondary standard is intended to provide public welfare protection, including protection against damage to vegetation.  The agency said a review of available data showed that an updated secondary standard of 70 ppb will provide requisite protection for public welfare, as required by the Clean Air Act.


A prepublication copy of the final ozone rule, the Regulatory Impact Analysis (RIA), and assorted Fact Sheets are available at

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