MCQ Detailed View

The ozone layer is a protective shield in the Earth's stratosphere that absorbs most of the Sun’s harmful ultraviolet (UV) radiation. Its depletion leads to increased UV rays reaching Earth’s surface, which can cause skin cancer, cataracts, and harm to ecosystems.

Among the gases listed, Chlorofluorocarbons (CFCs) are the main culprits in the depletion of the ozone layer. CFCs were widely used in refrigerants, aerosol sprays, and foam-blowing agents. When released into the atmosphere, they are stable and eventually reach the stratosphere, where they are broken down by UV radiation.

When CFCs break down, they release chlorine atoms. These chlorine atoms react with ozone (O₃) molecules and destroy them. One chlorine atom can destroy over 100,000 ozone molecules before it is removed from the stratosphere. This reaction leads to a significant thinning of the ozone layer, especially above the polar regions, creating what is known as the “ozone hole.”

Let’s break down the options:

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  Option A: Carbon dioxide contributes to global warming, not ozone depletion.

  
  


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  Option B: Chlorofluorocarbons are the primary agents that chemically destroy ozone molecules.

  
  


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  Option C: Nitrogen oxides contribute slightly to ozone damage but not as severely as CFCs.

  
  


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  Option D: Methane is a greenhouse gas and does not significantly affect the ozone layer.

  
  

Hence, the correct answer is Chlorofluorocarbons (CFCs). Their phasedown under international agreements like the Montreal Protocol has helped reduce further damage to the ozone layer.