Ozone (O3) is a gas composed of three oxygen atoms. It is not usually emitted directly into the air, but at ground-level is
created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight.
Ozone has the same chemical structure whether it occurs miles above the earth or at ground-level and can be "good" or "bad," depending on its
location in the atmosphere.
In the earth's lower atmosphere, ground-level ozone is considered "bad." Motor vehicle exhaust and industrial emissions, gasoline vapors, and
chemical solvents as well as natural sources emit NOx and VOC that help form ozone. Ground-level ozone is the primary constituent of
smog. Sunlight and hot weather cause ground-level ozone to form in harmful concentrations in the air. As a result, it is known as a summertime
air pollutant. Many urban areas tend to have high levels of "bad" ozone, but even rural areas are also subject to increased ozone levels because
wind carries ozone and pollutants that form it hundreds of miles away from their original sources.
"Good" ozone occurs naturally in the stratosphere approximately 10 to 30 miles above the earth's surface and forms a layer that protects life on
earth from the sun's harmful rays.
In 2004 EPA designated five areas (11 Counties) as nonattainment areas with respect to the 1997 8-hour ozone NAAQS [69 FR 23858]:
- Charleston (Kanawha and Putname Counties)
- Huntington (Cabell and Wayne Counties)
- Parkersburg (Wood County)
- Wheeling (Marshall and Ohio Counties)
- Weirton (Brooke and Hancock Counties)
Based on the 2002-2004 and 2003-2005 design values the DAQ submitted redesignation requests and maintenance plans for the Charleston, Huntington,
Parkersburg, Wheeling and Weirton areas. EPA approved the maintenance plans and redesignated each of the areas to attainment.
All areas of West Virginia are in attainment with the 1997 ozone NAAQS.
EPA is currently reviewing the ozone NAAQS. For more information see the EPA website.