The ozone layer, situated 15-30 km above the Earth's surface, protects life by absorbing harmful UV radiation from the sun. CFCs released into the atmosphere are destroying the ozone layer, with depletion rates highest in polar regions. This destruction increases harmful UV rays, risking skin cancer, eye cataracts, and damage to plants and small organisms. CFCs were widely used but are being phased out and banned due to their ozone-destroying effects.

1. What is ozone layer destruction?

2. The ozone layer, situated in the stratosphere about 15 to 30 km above the earth's surface, plays the important role of "space suit" that protects us living beings by absorbing harmful ultraviolet radiation (UVB) from the sun. The ozone layer is currently being destroyed by CFCs and other substances, its depletion progressing globally except in the tropical zone.

3. The ozone layer is disappearing at a particularly high rate in high-latitude areas. In the Antarctic Circle, a large ozone hole has been observed for eight consecutive years from 1989 through 1996.

4. Impact of ozone layer destruction Destruction of the ozone layer increases the amount of harmful ultraviolet radiation (UVB), which in turn can result in increased cases of skin cancer, and visual impediments such as cataract. It can also hinder the growth of plants and negatively impact small living organisms, such as zooplankton, phytoplankton, shrimp larvae and the young of fish.

5. What is CFC? CFC, chlorofluorocarbon, is the collective name for compounds made of carbon, fluorine, chlorine and hydrogen. Because of their stable, harmless and non-combustible properties, they are widely used in everyday applications such as cleansing agents for electronic components, coolants for air conditioners, foaming agents for the manufacture of insulating materials and so on. CFC variations include HCFC and HFC.

6. CFC (Chlorofluorocarbon) Because of CFC's strong ozone layer-destroying effect, its production was totally banned at the end of 1995. It is necessary to ensure proper handling of CFC in appliances currently in use. HCFC (Hydrochlorofluorocarbon) Although less powerful than CFC in destroying the ozone layer, HCFC must be also contained .

7. Mechanism of ozone layer destruction by CFCs Since CFCs are chemically stable, when released into the atmosphere they pass through the troposphere at about 20 km altitude without decomposing, reaching the stratosphere, where they are chemically decomposed by short-wavelength ultraviolet rays, releasing chlorine atoms. In a chain reaction, the chlorine atoms destroy the ozone layer in the stratosphere.

8. Prediction of future ozone layer destruction The 1994 general report of the scientific, environmental impact and technological economic assessment panel of the UNEP predicted that the amount of chlorine and bromine would peak in 1994 in the troposphere, while in the stratosphere it would reach peak 3 - 5 years later and begin to decrease, provided that all the signatory countries observe the revised Montreal Protocol of 1992. From this, it is predicted that the global ozone decrease will continue during the remaining years of the 20th century, but that if other factors remain unchanged, the ozone layer will begin to be restored in the early 21st century and the Antarctic ozone hole will disappear around the year 2045.

9. FINDING SOLUTIONS Despite the fact that, on the data known in the 1970s, the US Government banned the use of aerosols in 1978, it was not until 1987 that an international treaty, called the Montreal Convention, limiting the production of CFCs was signed by all the major industrial nations. The main users of CFCs agreed to reduce their consumption by 50% before the end of the century. However, experts said this reduction was insufficient and have suggested that a cut of 85% is needed if the ozone layer is to stand a chance of returning to normal within the next 50 years. That is how long it will take for harmful chemicals already in the atmosphere to work their way through.

10. Realising that the ozone layer was more badly damaged than previously thought, 82 countries and the European Community met in Helsinki in May 1989. They decided to phase out the production of all CFCs before the end of the century and to halt the use of other damaging chemicals as soon as possible. An added spur for phasing out CFCs is that they are also very potent greenhouse gases, some thousands of times more effective than carbon dioxide. (Greenhouse gases absorb heat radiated from the surface of the Earth, keeping it about 40° C warmer than it would be otherwise. Because of extra greenhouse gases in the atmosphere the world is gradually becoming warmer leading to changes in the climate and a rise in sea level). Such swift action on an environmental issue is unprecedented. From the realisation in 1985 that there was a problem, the causes have been identified and some solutions found. By the end of the century the ozone layer should be starting to recover.

11. PERSONAL RESPONSIBILITY While CFCs and other chemicals are being phased out we can all help reduce the damage to the ozone layer. Buy only CFC-free aerosols Carry out a survey of your home or the school's use of CFC products If your family is buying a refrigerator choose one which is more ozone friendly and which can be serviced without any coolant gas being released into the air. Most manufacturers supply the information needed to make a wise choice. Also try to make sure that there are arrangements for the coolant gases to be removed from the old refrigerator before it is broken up.