CBSE Class 9 Answered

Ozone is a layer in the stratosphere which extends from 20 -50 km from the Earth’s surface. It absorbs the harmful ultra violet rays of the sun coming towards the surface of the earth. Observation of holes in ozone layers has caused widespread concern among scientists and people. Depletion of ozone layer may result into the following disasters:

• Increased risks of skin cancer and various other diseases like cancer, cataract, blindness, sun burn etc. among humans. It may also leads to the weakening of the human immune system.
• Scientists have estimated that every 1% decrease in long-term stratospheric ozone would increase the incidence of these cancers by 2%.
• An increase of UV radiation would be expected to affect crops. A number of economically important species of plants, such as rice, wheat, barley, oats etc.
• Plankton (micro organisms in the surface layer of oceans) are threatened by increased UV radiation. Plankton forms the basis of the aquatic food chains.
• In domestic animals, UV overexposure may cause eye and skin cancers.

The rate of ozone depletion from 2014-2015 have not been released by the Ozone monitoring agencies. Between 1997 and 2000, the average rate of ozone depletion slowed by the equivalent of seven per cent per decade.