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What causes the depletion of the ozone layer?
We know that oxygen is O2. Oxygen molecule is made up of 2 atoms of oxygen combined together. Oxygen gas is essential for life because it is needed in respiration. Ozone is O3. Ozone molecule is made up of 3 atoms of oxygen combined together. Ozone is also a gas but it is poisonous in nature (if inhaled). Let us see how ozone is formed. Ozone is formed high up in the atmosphere by the action of ultraviolet radiation on oxygen gas. This happens as follows : The high energy ultraviolet radiation (UV radiation) coming from the sun splits oxygen gas into free oxygen atoms.
The free oxygen atoms thus produced are very reactive. One oxygen atom reacts with an oxygen molecule to form an ozone molecule :
At a height between 15 kilometres and 60 kilometres, there is a layer of ozone gas (O3) in the upper atmosphere. This ozone layer is very important for the existence of life on earth because it absorbs most of the harmful ultraviolet radiations coming from the sun and prevents them from reaching the earth. The ultraviolet radiations have extremely harmful effects on human beings, other animals as well as plants.
For example, ultraviolet rays can cause skin cancer. They also damage the eyes by causing an eye disease called cataract. Ultraviolet rays damage immune system by lowering the body’s resistance to diseases.
Thus, it is the ozone layer in the upper atmosphere which protects us from these diseases by absorbing ultraviolet rays coming from the sun.
It has now been found that the amount of ozone is getting depleted (or reduced) due to which the ozone layer in the upper atmosphere is becoming thinner and thinner day by day. The depletion of ozone layer is due to the use of chemicals called chlorofluorocarbons.
This happens as follows : Chlorofluorocarbons (CFC) are the chemicals which are widely used in refrigeration (refrigerators and air conditioners) as a coolant; in fire extinguishers and in aerosol sprayers. Chlorofluorocarbons released into the air react with ozone gas present in the ozone layer and destroy it gradually.
Due to this, the ozone layer in the upper atmosphere has become thinner, allowing more ultraviolet rays to pass through it to the earth. Thus, due to the depletion of ozone layer caused by chlorofluorocarbons, more ultraviolet radiations reach the earth.
If the ozone layer in the atmosphere disappears completely, then all the extemely harmful ultraviolet radiations coming from the sun would reach the earth. These ultraviolet radiations would cause skin cancer and other ailments in men and animals, and also damage the plants. All the life on the earth would be destroyed gradually. In 1987, in an attempt to protect ozone layer, the United Nations Environment Programme (UNEP) forged an agreement among its member countries to freeze CFC production at 1986 levels.