Which human-produced substances are known to deplete the ozone layer?

• A. Carbon dioxide and methane
• B. Chlorofluorocarbons and pesticides
• C. Nitrogen oxides and sulfur dioxide
• D. Harmless organic compounds

Answer: (B)

The depletion of the ozone layer is primarily caused by substances that release chlorine and bromine upon breakdown in the stratosphere. Chlorofluorocarbons (CFCs) are a major group of human-produced chemicals that have been widely used as refrigerants, propellants, and solvents. When CFCs reach the stratosphere, they are broken down by ultraviolet radiation, releasing chlorine atoms, which then react with ozone (O3) molecules and lead to the destruction of ozone.

Pesticides can also contain chemicals that contribute to ozone depletion, particularly those that include chlorine in their molecular structure, like certain organochlorine pesticides. These compounds can also release chlorine upon their breakdown, further impacting the ozone layer.

In contrast, the other options either include substances that do not significantly impact the ozone layer, such as carbon dioxide and methane, which are greenhouse gases but do not contribute to ozone depletion, or refer to nitrogen oxides and sulfur dioxide that may have complex interactions with ozone but are not primary contributors to its depletion. Harmless organic compounds are, as the name suggests, not known to harm the ozone layer at all. Thus, the correct association with ozone depletion is primarily with the chlorofluorocarbons