End of 2009 Ozone Season Finds AACOG Region in Compliance with Federal Air Quality Standards – For Now

When the U.S. Environmental Protection Agency (EPA) prescribed a significantly lower threshold for allowable ozone pollution in 2008, many predicted that the San Antonio region would join the ranks of numerous, primarily-urban areas of the country that are designated as “nonattainment” of the federal ozone standard. However, the 2009 ozone season, which ended on October 31, found the Alamo region still in attainment of the more stringent standard.  This accomplishment made San Antonio the largest U.S. city in full compliance with all national air quality standards.  It may be attributed in part to air quality improvements originating with the Early Action Compact of our Clean Air Plan[1] to the independent efforts of local governments, schools, businesses, and other organizations to conserve the use of fossil fuels (for example through the use of hybrid engines) and reduce ozone-producing practices (such as vehicle idling), to the US economy’s influence on general production and consumption trends in the region, and several other factors, such as the general wind speed and direction during the ozone season.

Based on a review of more than 1,700 scientific studies, the EPA had strengthened the ozone standard in 2008 to improve the law’s ability to protect human health and the environment. According to the 2008 standard, our area would remain in attainment if our fourth highest eight-hour average reading from any one of the three designated monitors in the Alamo region were no higher than 75 parts per billion (ppb) of ground-level ozone over a three-year period of time. Final designations of attainment under the 2008 revision were expected to be announced by the EPA no later than March 2010 based on data collected throughout the U.S. during the ozone seasons of 2007, 2008, and 2009. Our fourth highest reading for each of those years was 71, 78, and 75 ppb, respectively. Therefore, our three-year overall average was 74ppb, just under the EPA’s threshold of 75ppb.

On January 7, 2010, the EPA announced, however, that based on a review of the scientific studies and public comments that led to its 2008 standard revision along with input from the independent Clean Air Scientific Advisory Committee, it is now proposing that clean air threshold, which was set at 75ppb of ground-level ozone in 2008 over an eight-hour period, be lowered to between 60 and 70 ppb. The EPA has suggested that the ozone standard set in 2008 was perhaps not as protective of human health as it should have been. 

For two months following the January 7 announcement, the EPA will accept public comment.  It will hold three public hearings on the proposal, one of which will be in Houston on February 2, 2010, before a final decision is made regarding exactly where the new threshold shall ultimately be set.  The agency expects to announce its final decision in August 2010.  It expects that the new standard designations will be made by August 2011.

The proposed EPA revision to a lower acceptable level of ozone will significantly impact this region’s ability to remain in attainment of the clean air standard.  Because a designation of nonattainment would bring possible economic, industrial and transportation regulations and restrictions to our area, AACOG and its air quality partners are closely attuned to the EPA developments in this regard. In the meantime, it strives toward bringing cleaner, healthier air to the region through its ongoing planning, analysis, collaboration, outreach, and educational efforts.