The thinning of the ozone layer known as the ozone hole over polar regions is primarily caused by the release of which group of man made chemicals into the atmosphere?

Introduction / Context:
The term ozone hole refers to significant thinning of the protective ozone layer in the stratosphere, especially over Antarctica and sometimes the Arctic. This thinning allows more ultraviolet radiation from the Sun to reach the surface. Understanding its cause is important in environmental science and general knowledge. This question asks which chemicals are mainly responsible for creating the ozone hole.

Given Data / Assumptions:

• Several types of gases are released by human activities.
• Only some of them are directly linked to ozone layer depletion.
• The options include nitrogen oxides, hydrogen sulphide, chloro fluoro carbons, and carbon monoxide.
• We use standard environmental science findings.

Concept / Approach:
Chloro fluoro carbons, commonly abbreviated as CFCs, were widely used in refrigeration, air conditioning, aerosol sprays, and foam blowing agents. When these stable compounds reach the stratosphere, ultraviolet radiation breaks them down and releases chlorine atoms. A single chlorine atom can destroy many ozone molecules in a chain reaction, leading to thinning of the ozone layer. This process is the main cause of the ozone hole. Nitrogen oxides and carbon monoxide can affect air quality and climate but are not the primary cause of the polar ozone hole. Hydrogen sulphide also does not play the main role in this specific phenomenon.

Step-by-Step Solution:

Verification / Alternative check:
Environmental agreements such as the Montreal Protocol specifically targeted CFCs and related halogenated compounds for phase out because scientific studies had shown their strong role in ozone depletion. After reductions in CFC emissions, signs of slow recovery of the ozone layer have been observed. These global policy actions and scientific findings confirm that CFCs are the primary cause of the ozone hole.

Why Other Options Are Wrong:

• Nitrogen oxides contribute to smog and acid rain and can influence ozone chemistry but are not the main cause of the Antarctic ozone hole.
• Hydrogen sulphide is a toxic gas with a rotten egg smell but is not a key driver of stratospheric ozone depletion.
• Carbon monoxide affects air quality and health at ground level but does not directly destroy ozone in the way that chlorine from CFCs does.

Common Pitfalls:
Students sometimes confuse greenhouse gases responsible for global warming with ozone depleting substances. While some compounds can have both effects, CFCs became famous mainly for damaging the ozone layer, not for trapping heat. Keeping the roles separate helps: carbon dioxide is the main greenhouse gas, and CFCs are the main ozone layer destroyers.

Final Answer:
Chloro fluoro carbons (CFCs) used in old aerosols and refrigerants