The chlorofluorocarbons (CFC) refrigerants containing chlorine have been found to be one of the major causes of the destruction of the ozone layer. Ozone layer is located in the earth’s stratosphere at the distance of 11 km from the surface of the earth. It prevents the ultraviolet rays of the sun from coming to the surface of the earth. The ultraviolet rays are the high intensity rays of the sun that have been found to cause skin cancer, melting of the polar ice, etc. If the ozone layer is destroyed by the CFCs the ultraviolet radiations travel to the surface of the earth and cause wide scale destruction.
The main cause of the depletion of ozone layer is chlorine that reacts with ozone and converts it into oxygen, which does not have the capacity to block the ultraviolet radiations of the sun. CFCs contain more than one atom of chlorine in their compounds. CFCs are heavier than air, but their life is very long, sometimes even extending to a hundred years. In due course of time they start moving in the upper layers of atmosphere and eventually reach the stratosphere where ozone is present. The time taken by the CFCs to reach these higher levels may be a decade or even more, but as long as they are in the atmosphere they pose the danger to the ozone layer.
When CFCs reach the stratosphere, chlorine atoms get separated and they react with ozone layer, converting it into oxygen. The process of the depletion of ozone layer is extremely slow.
In the year 1987, scientists observed the ozone hole (ozone depleted area), over the polar ice caps in the spring season. This has been a great cause of concern. According to scientists, if the escape of the CFCs to the atmosphere is not controlled, there can be dire consequences in future.
Different CFC refrigerants have different capacities to destroy the ozone layer depending upon their chlorine content and life of the compound in the atmosphere. The term “Relative Ozone Destruction Efficiency” describes the destructive potential of the CFCs. This factor is one for R-11, as it has maximum potential to destroy the ozone layer. On the other hand R-22 having value 0.05 has the least potential.
In 1987 a conference was held where it was decided to phase out the production of CFCs and develop the suitable substitute refrigerants that have no ozone depletion potential. The protocol which came to be popularly known as “Montreal Protocol” was signed by a number of countries to phase out the production of CFCs by January 6, 1996 in the developed countries and by 2000 in the developing countries. However, the protocol was amended at the London Conference in June 90. As per the amendment the CFCs have to be phased out by 2000 in the developed countries and by 2040 in the other countries.
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