(i) Ozone layer present in the stratosphere absorbs the harmful UV rays from the sun. The ozone molecule (O₃) is continuously degrading and forming in the atmosphere.

(ii) Lately, due to the usage of CFCs (Chlorofluorocarbons), the balance between the formation and degradation of ozone has been disturbed. The CFCs release Cl on reacting with UV rays in the atmosphere and Cl then further breaks down ozone molecules.

(iii) Since Cl only acts as catalyst and is not actually utilised in the reaction, hence the damage due to the current present CFCs in the atmosphere is permanent and continuous.

(iv) Although ozone depletion is widely spread all through the stratosphere, it is particularly present over the Antarctic region. The ozone layer over the area is particularly thinned and hence is also referred to as Ozone hole.

Enhanced exposure to ultraviolet rays is harmful as:

(i) Excessive exposure to UV rays might cause mutations in the cells and can be extremely harmful.

(ii) It can cause skin aging, damage to skin cells and various types of skin cancers.

(iii) In human eye, cornea absorbs UV-B radiations and prolonged exposure might cause inflammation of cornea, called snow blindness, cataract etc. It can also cause permanent cornea damage in extreme cases.