Ozone Depletion -- Can It Be Controlled?




by Evan McCulty--Roane County

Delivering the keynote address at the 10th anniversary of the Vienna Convention for the Protection of the Ozone Layer in December, 1995, Dr. Rumen D. Bojkov of the World Meteorological Organization (WMO) reiterated the consensus of his peers that the "fragile state of the ozone layer" is one of the most serious environmental problems that we face today. ("Review of the State of the Ozone Layer " ) Ozone depletion may upset the fragile balance of the entire global ecosystem and ". . . is a serious environmental concern because more ultraviolet-B (VB) radiation from the sun reaches the surface as the Earth's protective ozone layer becomes thinner." ("State of the Stratospheric Ozone " ) In 1990 an all-party committee produced a report entitled, "Deadly Releases - CFCs." This report began with the following conclusion:

We, the members of the committee, have
reached one overpowering conclusion -- not just a
concensus, but a unanimous opinion -- that ozone
depletion is a threat to the continuation of life on
Earth. ("Deadly Releases - CFCs ")

Ozone forms a layer that shields the Earth against ultraviolet radiation produced by the sun. The ozone layer is primarily located in the Earth's stratosphere, the section of the atmosphere between 35 and 80 kilometers above the Earth's surface (Lipkin 199) . If compressed at sea level, the ozone layer would be no more than three millimeters thick (Gay 9) . An ozone molecule is a compound of three oxygen atoms, unlike the oxygen molecule in the air we breathe that contains only two oxygen atoms (Lipkin 199) . Unfortunately, since the time of that release, things have only become worse. Various factors have contributed to the depletion of the ozone layer, the region of the atmosphere that protects us from ultra violet radiation; however, measures have been taken to reduce the environmental hazards of ozone depletion and to prevent further damage.


Recently, scientists have recorded a decline in stratospheric ozone levels from ten to thirty percent. It is predicted that as the ozone layer thins, there will be increased incidents of skin cancer and eye cataracts, as well as extensive crop damage, destruction of marine life, and immune suppression (Rayloff 260) . If this would occur, it could cripple the economy and destroy our way of life. According to the Environmental Protection Agency, there will be an increase of approximately twenty thousand skin cancer cases for every one percent decrease in stratospheric ozone levels ("Protection of the Ozone Layer") . If the ozone layer were to be totally destroyed, all life on Earth would be eradicated. Life could only exist in the deepest seas, where there is no light.

Ozone is absolutely necessary in the stratosphere to protect the Earth, but ozone in the lower atmosphere is a harmful air pollutant. Low atmospheric ozone is a by-prodeuct of fossil fuel burning. It is also the main source of the world's smog. Large cities have the greatest concentration of smog due to the high number of automobiles and factories in a relatively small area. Smog makes it hard to breathe and is irritating to the eyes. The elderly are more likely to feel the effects of air pollution than the general public ("Frequently Asked Questions About Ozone") .

Ozone depletion has been linked primarily to chlorofluorocarbons (CFCs), nitrogen oxides (NOx), and the halogens (Rayloff 260; Lipkin 199) . CFCs are used as cooling agents in refrigerators and air conditioners, as blowing agents for foam insulation, and as cleaning agents in electronics manufacturing. In some countries they are even used as propellants for aerosol sprays ("Grave Threat to Earth's Protective Ozone Layer") . Before the link was made between CFCs and ozone depletion, CFCs were considered an ideal chemical compound because of their properties. They are nonflammable and nontoxic. Because of their stable nature, CFCs remain intact in the atmosphere for many years, and eventually work their way up to the stratosphere. Once in the stratosphere, ultraviolet light breaks apart the CFC compound. This frees a chlorine atom to catalyze a reaction which converts ozone molecules to oxygen molecules. Ocygen molecules cannot provide the same protection from ultraviolet radiation. A single CFC molecule can have a lifespan of over one hundred years. In this time one CFC molecule may be responsible for the destruction of an many as 100,000 ozone molecules ("Grave Threat") .

In 1985 a hole in the ozone layer was discovered over Antarctica and has become more extensive in the past few years. It now covers approximately 23 million square kilometers, about the size of North America (Adler 230-231) . A new study suggests that the Antarctic ozone hole may be self-reinforcing. It apparently prolongs its life each year by cooling the stratosphere, and it may even strengthen itself from one year to the next, regardless of any change in CFC concentrations (Zimmer 28-29) . As night settles over the South Pole and the atmospohere there gets progressively colder, the temperature difference between the Antarctic and the sunlit region of the planet increases. The temperature contrast produces a pressure difference that drives strong wind bands in the stratosphere. The result is a stable wind pattern that traps cold air over the South Pole. The temperature in the stratosphere over Antarctica can then drop to 120 degrees below zero (Zimmer 29; Horgan 28-29) .

These cold temperatures allow clouds of ice crystals to form, which hold chlorine and other ozone damaging elements over Antarctica. The ozone destroying reactions are driven by ultraviolet radiation, so they do not begin in earnest until the sun rises over the Antarctic in the spring. The reactions continue until the sun has warmed the stratospohere enough to melt the ice crystals and break up the wind patterns. The time required to warm the stratosphere is inversely proportional to ozone concentrations. Antarctica's low ozone concentration extends the amount of time required to warm its stratosphere. Therefore, the ozone destroying reactions, wind patterns, and ice crystals are prolonged over Antarctica each year (Zimmer 29) .

Natural disasters, such as volcanoes, also contribute to the destruction of the ozone layer. Scientists believe that volcanic eruptions are accelerating the erosion of stratospheric ozone. In years of major volcanic eruptions, the sulfur released from the volcano can greatly reduce ozone concentrations in the region of the stratosphere between ten and twelve kilometers. This region of the stratosphere is usually too warm to support the growth of ice crystals; therefore, without the presence of sulfur it has a slower rate of destruction (Volcanic Bite" 365) . The accelerated destruction from an eruption can even spread to the tropical regions where the intense heat normally suppresses ozone-destroying reactions. After a recent eruption, scientists observed ozone levels in the tropics to be ten percent lower than any previously measured. Scientists have predicted that a major volcanic eruption could trigger ozone losses of more than thirty percent in mid-latitudes (Horgan 28) .

In 1987 an international convention was held in Montreal to discuss some possible solutions to ozone depletion ("Protection ") . This meeting resulted in 74 nations having committed themselves under the Montral Protocol to reducing the production of chlorofluorocarbons by the year 1998. More recently, several industrial countries, including the United States, have called for a total phase-out by the year 2000. DuPont, the world's largest producer of CFCs, has announced that it plans to phase out future production of CFCs by the end of the century ("Grave"; Zimmer 29) . The nations of the world are coming together to try and save the ozone layer, but the problem is over our heads every day. "If all CFCs and other chlorine sources were cut off today," remarks J. R. Herman of the NASA Goddard Space Flight Center, "chlorine levels would continue to rise in the stratosphere for another 20 or 30 years." (Horgan 29) .

The destruction of the ozone layer is a very important issue. Its destruction is the result of many contributing factors, both man-made and naturally occurring. The naturally-occurring factors are uncontrollable, but the man-made factors are not. It is the responsibility of everyone to drastically reduce, and eventually eliminate all man-made factors. Seventy-four nations have already committed themselves, under the Montreal Protocol, in trying to reduce any further damage to the ozone layer. There are no "quick fixes" to reverse the damage already done. We must find ways to prepare for changes in our environment, and hopefully the ozone layer will repair itself in time.
Works Cited

Adler, T. "The Seasonal Ozone Decline Continues." Science News 8 Oct.1994: 230-231,

"Deadly Releases - CFCs." Online. World Wide Web.
http://www.Lycos.com>ozone. 8 Mar. 1996.

Dudek, Daniel J. "Grave Threat to Earth's Protective Ozone Layer."
Online. World Wide Web. http://www.edf.org. 8 Mar. 1996.

"Frequently Asked Questions about Ozone." Online. World Wide Web.
http://www.Lycos.com>ozone . 8 Mar. 1996.

Gay, Kathlyn. Ozone . New York: Impact, 1989.

Horgan, J. "Volcanic Disruption." Scientific American March 1992: 28-29.

Lipkin, R. "Accounting for Missing Airborne Ozone." Science News
24 Sept. 1994: 199.

"Protection of the Ozone Layer." Online. World Wide Web.
http://www.Lycos.com>ozone . 8 Mar. 1996.

Rayloff, J. "Radical News About SSTs and Ozone." Science News
 22 Oct. 1994: 260.
"Review of the State of the Ozone Layer." Online. World Wide Web.
http://www.Lycos.com>ozone . 8 Mar. 1996.

"State of Stratospheric Ozone." Online. World Wide Web.
http://taylorb@aesvan.dots.doe.ca. 8 Mar. 1996.

"Volcanic Bite Out of Antarctic Ozone." Science News 30 May 1992: 365.

Zimmer, C. "Son of Ozone Hole." Discover Oct. 1993: 28-29.