Ozone Air Quality Standards: EPA’s Proposed January 2010 Revisions

James E. McCarthy
Specialist in Environmental Policy

EPA Administrator Lisa Jackson signed proposed changes to the National Ambient Air Quality Standards (NAAQS) for ozone on January 6, 2010. The proposal appeared in the Federal Register on January 19. NAAQS are standards for outdoor (ambient) air that are intended to protect public health and welfare from harmful concentrations of pollution. By changing the standard, EPA would be concluding that protecting public health and welfare requires lower concentrations of ozone pollution than it previously judged to be safe. Under the proposed standards, as many as 96% of the counties that currently monitor ozone might need to take action to reduce emissions. The proposal would also, for the first time, set a separate standard for public welfare, the principal effect of which would be to call attention to the negative effects of ozone on forests and agricultural productivity. 

The ozone standard affects a large percentage of the population: as of November 2009, 122 million people (about 40% of the U.S. population) lived in areas classified "nonattainment" for the primary ozone NAAQS. As a result of the standard's strengthening, more areas will be affected, and those already considered nonattainment may have to impose more stringent emission controls. 

The proposed revision would lower the primary (health-based) standard from 0.075 parts per million – 75 parts per billion (ppb)—averaged over 8 hours to somewhere in the range of 70 to 60 ppb averaged over the same time. Using the most recent three years of monitoring data, 515 counties (76% of all counties with ozone monitors) would violate the new standard at 70 ppb; 650 counties (96% of those with monitors) would be in nonattainment if the standard is set at 60 ppb. By comparison, only 85 counties have monitors showing exceedance of the currently implemented 1997 standard. Thus, the change in standards will likely have widespread impacts in areas across the country. (The counties that might exceed the proposed standard are shown in Figure 2 of this report.) 

The proposed standards, when finalized in August 2010, will set in motion a long and complicated implementation process that has far-reaching impacts for public health, for sources of pollution in numerous economic sectors, and for state and local governments. The first step, designation of nonattainment areas is expected to take place in the summer of 2011, with the areas so designated then having 3 to 20 years to reach attainment. 

The proposed standards raise a number of issues, including whether they should lead to stronger federal controls on the sources that contribute to ozone pollution. Current federal standards for cars, trucks, nonroad vehicles and engines, power plants, and other stationary pollution sources are not strong enough to bring many areas into attainment, thus requiring local pollution control measures in many cases. 

EPA, the states, and Congress may also wish to consider whether the current monitoring network is adequate to detect violations of a more stringent standard. Only 675 of the nation's 3,000 counties have ozone monitors in place. 

This report discusses the standard-setting process, the specifics of the new standard, and issues raised by the Administrator's choice; and it describes the steps that will follow EPA's promulgation.


Date of Report: February 1, 2010
Number of Pages: 15
Order Number: R41062
Price: $29.95

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