Question

Ozone-layer is getting depleted because of
a. Excessive use of automobiles
b. Excessive formation of industrial units
c. Excessive use of man-made compounds containing both fluorine and chlorine
d. Excessive deforestation

Answer 1

Hint: Compounds containing elements known as halogens are mainly responsible for ozone depletion. The elements are highly electronegative and are non-metallic.

Complete answer
The thinning of the ozone layer due to depletion in the concentration of ozone molecules is known as ozone depletion. The major substances responsible for ozone depletion include chlorofluorocarbons or CFCs. These are compounds containing chlorine and fluorine. Almost 14% of the total depletion is caused by CFCs. Only one atom of chlorine and convert one lakh molecules of ozone into oxygen.

Additional Information:
Several Global efforts have been made to reduce the ozone depletion and global warming phenomenon:

- Montreal Protocol: Limitations were placed on the use and production of ODS or ozone-depleting substances like CFC and HFC.

- Intergovernmental Panel on Climate changes: Established a world climatic system.

- Kyoto Protocol: Its main aim was to reduce the emission of greenhouse gases.

- Beijing Protocol: Its aims were similar to that of the Montreal Protocol, which was to reduce the emission of ozone-depleting substances.

- UN Convention on Climate Change: The main aim was to bring a reduction in global warming rates.

- World Earth Summit: It focused on the idea of sustainable development without the depletion of biodiversity.

Major effects of ozone depletion include:

- Skin cancers

- UV-B radiation is absorbed by the cornea and this may result in snow blindness or cataract.

- DNA mutation due to exposure to radiation can increase the chances of mutations

Reduction in the potential of the immune system.

So, the correct answer is,” Ozone-layer is getting depleted because of excessive use of man-made compounds containing both fluorine and chlorine.”

Note: It has to remember that the maximum potential of ozone depletion by CFCs is due to the release of the chlorine atom. Other compounds like nitrogen oxide, sulphur dioxide, halon, carbon tetrachloride, methyl chloroform, chlorine, etc can also cause ozone depletion. Another group of a compound named HFCs or hydrofluorocarbons also cause ozone depletion in a similar way to CFCs. These substances react with ozone and convert it into oxygen.