Ozone (O3) is a gas composed of three oxygen atoms, unlike the diatomic oxygen (O2) we must breathe. Ozone is not usually emitted directly into the air. At ground-level, ozone is created by chemical reactions between diatomic oxygen (O2), nitrogen oxides (NOX) and volatile organic compounds (VOCs) in the presence of sunlight. Motor vehicle exhaust, industrial emissions, gasoline vapors, chemical solvents, and some natural sources emit NOX and VOCs.
Ozone can be "good" or "bad" depending on its location in the atmosphere. The natural ozone layer in the upper atmosphere absorbs most of the sun’s damaging ultraviolet radiation. Ground-level ozone in the lower atmosphere is considered "bad." Many urban areas tend to have high levels of "bad" ozone, but even rural areas can have high ozone because wind carries it and its precursor pollutants hundreds of miles away from their original sources.
There is one primary and one secondary federal standard for ozone. Several Oklahoma sites are close to exceeding the standard.
Ozone is a serious air quality problem in many parts of the United States. Even at low levels, ozone can cause negative health effects. People with lung diseases, children, older adults, and people who are active outdoors may be particularly sensitive to ozone. Numerous scientific studies have linked ozone pollution exposure to a variety of problems, including:
2008 Primary and Secondary Ozone Standard = 0.075 parts per million (8-hour average)
2015 Primary and Secondary Ozone Standard = 0.070 parts per million (8-hour average)
Effective December 28, 2015, the EPA revised the national ambient air quality (NAAQS) standards for ozone. The primary and secondary standards were tightened from 0.075 parts per million (ppm) to 0.070 ppm. To compare to the standard (either 0.075 or 0.070 ppm), 8-hour average concentrations are tracked, and the fourth-highest daily maximum is averaged across three consecutive years. The chart compares monitored values to the 2008 standard because it was in effect for the majority of 2015.
2015 Ozone Values vs. 2008 NAAQS
3 yr avg ('13-'15) 4th highest daily max
8 hr avg Ozone concentration (ppm)