Ozone is a form of oxygen, the molecule contains three oxygen atoms and has the same chemical structure whether it is found high in the atmosphere or at ground-level. Ozone is unstable and will readily combine with other atoms.
High in the atmosphere "stratosphere ozone" is present, and protects against ultraviolet radiation. In contrast to the "good" ozone in the stratosphere, ozone can present a problem at certain concentrations at ground-level. It is generated both from certain types of pollution and natural sources, including when atmospheric conditions cause stratospheric ozone down toward the earth's surface.
Ozone is an air pollutant that can damage human health, vegetation, and many common materials. It is an ingredient of urban smog. Unlike most other air pollutants, ozone is not directly emitted from any one source. Ozone is formed near the surface by the interaction of sunlight, with hydrocarbons and nitrogen oxides. Those pollutants are emitted by transportation and industrial sources.
Production of cleaner burning fuels, reduction of gasoline vapors at fueling stations and emission controls at refineries are among the contributions the petroleum industry is making to reduce hydrocarbons and nitrogen oxides for ground-level ozone.
What Can I Do?
Using gasoline wisely reduces the pollutants that form ozone, please review the Fuel-Saving Tips for Drivers to see what you can do help. Emission controls at gasoline stations keep the fuel loading emissions from escaping into the atmosphere. When the pump stops, don't top off your tank if you want to reduce the hydrocarbon vapors from going into the air.