Explain why stratospheric ozone is important while ground-level ozone is considered a pollutant. What is the role of CFCs in stratospheric ozone depletion? What was the worldwide reaction once the connection between CFCs and ozone depletion was well understood?

Stratospheric ozone is important because it acts as the blockade to harmful UV radiation directly from the Earth. If there were no stratospheric ozone then the life on the Earth was not possible because direct exposure to UV rays cause Skin cancer and many more health problems to humans and animals and plants. Thus, Stratospheric ozone is very important because it absorbs the penetration of harmful UV radiation as well as other harmful radiations. Whereas, the ground level Ozone becomes a harmful gas because it has adverse effect on the Human lungs. Old aged people, children, outdoor working people etc. mostly get effected in their breathing and taking smooth air from the environment.

The role of Ozone depletion in the stratosphere by the CFCs is very crucial because 1 molecule of CFC can destroy 100,000 molecules of Ozone by a simple chemical reaction in the presence of UV. More the CFCs in the environment and in the Stratosphere cause more Ozone depletion. And, this may lead to penetration of harmful UV rays into the Earth surface.

When the connection between CFCs and ozone depletion was well understood, many of the people (scientists, business persons, public, politicians) started to adopt the tecchnology which do not produce CFCs. Till few years ago, our refrigerator, AC and other instruments used to produce enough CFCs but, nowadays this has been significantly reduced. Similarly, the burning of plastics and other CFCs producing fuels has been banned or reduced. All the concerned authorities made strong rules to reduce CFCs in the environment and in the Atmosphere. And, this led to decrease in the depletion of Ozone on the stratosphere.