There is a layer of ozone gas in the upper atmosphere at a height between 15 kilometers and 60 kilometers. This ozone layer is very important for the existence of life on earth because ozone layer absorbs most of the harmful ultra-violet radiations coming from the sun which can cause skin cancer. The ozone forms a thick layer in Stratosphere encircling the earth that has large amount of ozone in it. Now it is found that the amount of ozone is getting depleted (reduced) due to which the ozone layer in the upper atmosphere is becoming thinner and thinner day by day.
The main reason of the depletion of ozone layer is the use of man-made chemicals namely halocarbon, refrigerants, solvents, propellants, fluoro carbon and chloro-fluoro-carbons. These compounds are transported into the stratosphere by wind. They react with ozone gas and destroy it gradually and cause breakdown of ozone into oxygen. Thus the use of these chemicals deplete ozone layer.
There are other ozone depleting substances such as Methyl Bromide used in pesticides, Halons used in fire extinguisher and Methyl chloroform used in making industrial solvents. As such the industries manufacturing insulating foams solvents, soaps, air conditioner, and refrigerator are creating chemicals which are depleting ozone layer.
In this discussion, we conclude that if ozone layer in the atmosphere disappears completely, then all the harmful ultra-violet radiations coming from the sun would reach the earth. These ultra-violet radiations would cause skin cancer in human and animals. It also damages the plants. All the life on earth would then be gradually destroyed.