North Carolina has attained all federal clean air standards for the first time since 1997, the U.S. Environmental Protection Agency said Wednesday.
The breakthrough resulted with the Charlotte metro area, which has the state’s dirtiest air, meeting the 2008 federal standard for ground-level ozone. Charlotte’s reading for ground-level ozone, or smog, is 73 parts per billion for 2012-2014.
The federal limit is 75 parts per billion. During the same three-year period, the Triangle’s ozone reading was 66 parts per billion. The lowest in the state was 57 in Bryson City, near the Great Smoky Mountains National Park.
As recently as the late 1990s, ozone levels in the Triangle and Charlotte exceeded 100 parts per billion. The state’s worst ozone has historically been concentrated in the Mecklenburg County area, followed by Winston-Salem and the Triad.
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Ground-level ozone is a chemical compound that results from the interaction of nitrogen oxides with sunlight and heat. The most common health effects associated with ozone are respiratory problems and irritated lungs.
The major cause of ground-level ozone is automobile exhaust. Air quality has improved dramatically around the country as cars, trucks, power plants and industrial facilities become more efficient. The air quality improvements are the result of federal and state legislation requiring fuel-efficiency improvements, catalytic converters and other measures.
Much of the work in setting the nation’s ozone limits is done in Research Triangle Park by EPA’s Office of Air Quality Planning and Standards.