Ozone Depletion

Ozone is a form of oxygen—three atoms to a molecule instead of the usual two. When ozone exists in the atmosphere at ground level, it contributes to smog. But ozone in the stratosphere, from 5 to 30 miles above the Earth's surface, protects life by absorbing harmful ultraviolet (UV) radiation from the sun.

In the 1970s scientists began to suspect that certain human-produced chemicals were damaging the ozone layer in the stratosphere. In the 1980s scientists discovered that the ozone layer above Antarctica was greatly reduced each spring. This became known as the Antarctic ozone hole. Chlorofluorocarbons (compounds containing chlorine, fluorine and carbon) were among the chemicals that were found to cause ozone depletion. Chlorofluorocarbons, or CFCs, were commonly used at the time as refrigerants (e.g., freon) and as propellants in aerosol cans.

Under the auspices of the United Nations Environment Programme (UNEP), the Vienna Convention for the Protection of the Ozone Layer was negotiated in 1985. The Vienna Convention obligated signatory countries to study the problem of ozone depletion. In 1987 the Montreal Protocol on Substances That Deplete the Ozone Layer was negotiated. The Montreal Protocol obligated signatory countries to actually reduce the production of CFCs and other ozone-depleting chemicals.

World-wide production and use of CFCs and other ozone-depleting chemicals have fallen dramatically, and the ozone layer in the stratosphere is starting to recover.

The United States has ratified both the Vienna Convention and the Montreal Protocol. The U.S.—along with Canada, Sweden and Norway—banned the use of CFCs in consumer aerosols in 1978, before either treaty was negotiated. Many people are surprised to learn that CFCs were banned in consumer aerosols that long ago.

If you are interested in additional information, you may find the following web sites helpful:

Wikipedia article on ozone depletion
UNEP Ozone Secretariat
U.S. EPA web site on ozone depletion