Ozone in the United States

Ozone (Os) in Environmental Law

A form of oxygen composed of three molecules of oxygen instead of the more common combination of two. Ozone is important in two environmental situations: it is a pollutant at ground level; and it protects the earth from ultraviolet radiation in the stratosphere. Both types of ozone get special attention in the Clean Air Act Amendments of 1990.

Ozone at ground level is one of the five most common air pollutants. It is highly poisonous gas that reduces the amount of oxygen inhaled and can cause severe respiratory problems. It is regulated by the Environmental Protection Agency through the National Ambient Air Quality Standards, which establish air quality criteria for common contaminants. Each state must have a plan designed to bring the state’s air quality into compliance with the standards and then maintain the air quality. See nitrogen oxides; nonattainment areas; state implementation plan.

Ozone is not directly discharged, like many pollutants. Instead, it is created by chemical reactions involving other pollutants called precursors. The precursors for ozone are volatile organic compounds and nitrogen oxides released by motor vehicles and by some manufacturing processes, primarily during the use of internal combustion engines. Ozone formation is most rapid in the summer, and topography and winds play a role. If the area is in a depression, the gases tend to remain where they are, and chemical reactions can occur. However, winds tend to move the precursors away from their origins and cut down on the formation of the soup.

Stratospheric ozone is a buffer that has protected the earth from ultraviolet rays for millennia. However, the depletion of stratospheric ozone has been documented for years, caused by chemicals used for refrigeration, propellants, and fire suppression [see chlorofluorocarbons]. As a result of international concern and agreements, the chemicals responsible for ozone depletion are being phased out of production and use. The 1990 amendments to the Clean Air Act devote an entire title to stratospheric ozone. See also Montreal Protocol.
Based on “Environment and the Law. A Dictionary”.