Ozone is a gas comprised of three atoms of oxygen that is found both in the Earth’s upper atmosphere and at ground level. According to the US Environmental Protection Agency, ozone can be good or bad, depending on where it is found.
According to the federal government’s AirNow.gov website, ozone occurs naturally in the Earth's upper atmosphere – 6 to 30 miles above the Earth's surface – where it forms a protective layer that shields us from the sun's harmful ultraviolet rays.
Manmade chemicals are known to destroy this beneficial ozone. An area where the protective "ozone layer" has been significantly depleted – for example, over the North or South Pole – is sometimes called "the ozone hole.” The United States, along with over 180 other countries, recognized the threats posed by ozone depletion and, in 1987, adopted a treaty called the Montreal Protocol to phase out the production and use of ozone-depleting substances. EPA has established regulations to phase out ozone-depleting chemicals in the United States.
In the Earth's lower atmosphere, near ground level, ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight. Ozone at ground level is a harmful air pollutant.
Ozone in Wyoming:
In July 2012, the U.S. Environmental Protection Agency designated all of Sublette County and portions of Lincoln and Sweetwater counties as an ozone nonattainment area, collectively known as the Upper Green River Basin Ozone Nonattainment Designation Area (UGRB). All other areas of the State of Wyoming are in attainment.