How Ozone layer depletion occurs? Add note on it’s effects? (ACF 2018)

  • Ozone depletion is the gradual thinning of the ozone layer in the Earth’s stratosphere. 
  • The ozone layer is a region of Earth’s stratosphere that absorbs most of the Sun’s ultraviolet (UV) radiation. 
  • It contains high concentrations of ozone (O3) relative to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. 
  • The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth’s atmosphere as a whole is about 0.3 parts per million.

Ozone-depleting substances (ODS):

  • Ozone depletion is caused by human activities that release certain chemicals into the atmosphere. These chemicals, known as ozone-depleting substances (ODS), can break down ozone molecules in the stratosphere. 
  • The main ODS are chlorofluorocarbons (CFCs), halons, hydrochlorofluorocarbons (HCFCs), and methyl chloroform. 
  • CFCs were once widely used in refrigerators, air conditioners, and other products. Halons were used in fire extinguishers. HCFCs were used as substitutes for CFCs in some products. Methyl chloroform was used as a solvent.


  • ODS are released into the atmosphere from a variety of sources, including industrial emissions, vehicle emissions, and the use of certain products. 
  • Once released into the atmosphere, ODS can take many years to reach the stratosphere. In the stratosphere, ODS are broken down by ultraviolet radiation, releasing chlorine and bromine atoms. These atoms then react with ozone molecules, destroying them.
  • Ozone depletion has a number of negative effects on human health and the environment. Increased exposure to UV radiation can cause skin cancer, cataracts, and other health problems. UV radiation can also damage plants and animals. In addition, ozone depletion can contribute to climate change.
  • The Montreal Protocol is an international treaty that was signed in 1987 to protect the ozone layer. The treaty phases out the production and use of ODS. As a result of the Montreal Protocol, the production of CFCs has been phased out in most countries. 
  • The ozone layer is slowly recovering, but it is expected to take many years for it to fully recover.

Effects of ozone depletion:

  • Increased risk of skin cancer: UV radiation can cause skin cancer, and ozone depletion increases the amount of UV radiation that reaches the Earth’s surface.
  • Increased risk of cataracts: UV radiation can damage the eyes, and ozone depletion increases the risk of cataracts.
  • Suppressed immune system: UV radiation can suppress the immune system, making people more susceptible to infections.
  • Damage to plants and animals: UV radiation can damage plants and animals, disrupting food chains and ecosystems.
  • Climate change: Ozone depletion can contribute to climate change by allowing more UV radiation to reach the Earth’s surface.

Ozone depletion is a serious problem that has a number of negative effects on human health and the environment. The Montreal Protocol is an important international treaty that is helping to protect the ozone layer. However, it will take many years for the ozone layer to fully recover.

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