Why depletion of ozone layer a cause of concern?

Ozone layer is a high concentration of ozone molecules present in the stratosphere.
The main function of the ozone layer is to absorb the Sun's ultraviolet radiation, hence protecting the Earth from its harmful effects.
Depletion of the ozone layer is  caused due to excessive use of CFCs or Ammonia
Damage of ozone layer is  a cause of concern because ultraviolet radiation from the sun will reach the earth and will effect human beings, plants and animals through genetic mutations, skin cancers and cataracts 
After the Montreal Protocol, the Ozone layer is improving by the controlled use of CFCs and other harmful chemicals.