There are two general definitions of ozone: “Good” ozone and “bad” ozone. Ozone in the upper atmosphere, known as the “ozone layer,” protects us from the sun’s harmful ultraviolet rays. It provides a protective shield against harmful ultraviolet waves.

Ground level ozone is more commonly known as “smog.” It is primarily a summertime air pollution problem, and is the primary pollution concern in Central Oklahoma. Ozone is formed on hot days, when the wind is low and there is an intense presence of sunlight. Ozone is created by a mixture of gases known as nitrogen oxides (NOx) and volatile organic compounds (VOCs). NOx is emitted from motor vehicles, power plants and other sources of combustion. VOCs are emitted from a variety of sources, including motor vehicles, chemical plants, refineries, factories, consumer and commercial products such as gasoline-powered lawn care equipment, and other industrial sources.

Changing weather patterns contribute to yearly differences in ozone concentrations from region to region. Also, ozone and the pollutants that cause ozone can be carried to an area by wind from pollution sources located hundreds of miles away.

A substantial percentage of ozone in Central Oklahoma results from mobile sources. While new vehicles emit far fewer pollutants than ever before, increased vehicle trips and pollution from small engines are great contributors.

Typically, August is the worst month for high ozone levels. The bulk of ozone “Alert Days” and high readings occur between late June and mid-September. Aberrant weather conditions, though, can cause surges of high levels at any time of the summer.