The ozone layer depletion is primarily caused by which compound?

The ozone layer depletion is primarily caused by which compound?

• A. Chlorofluorocarbons
• B. Methane
• C. Water vapor
• D. Nitrogen

Answer: (A)

Chlorofluorocarbons are the main culprits because they are stable in the lower atmosphere but break down under UV light in the stratosphere to release chlorine atoms. Those chlorine atoms initiate catalytic cycles that repeatedly destroy ozone molecules: a chlorine atom reacts with ozone to form chlorine monoxide and oxygen, and then the chlorine monoxide reacts with another oxygen atom to release chlorine again and produce more oxygen. This means one chlorine atom can convert many ozone molecules into regular oxygen, thinning the ozone layer that blocks harmful UV radiation. The other substances listed—methane, water vapor, and nitrogen—affect atmospheric chemistry in various ways, but they do not drive the primary depletion of the ozone layer in the same direct, catalytic way as chlorine from CFCs.

Chlorofluorocarbons are the main culprits because they are stable in the lower atmosphere but break down under UV light in the stratosphere to release chlorine atoms. Those chlorine atoms initiate catalytic cycles that repeatedly destroy ozone molecules: a chlorine atom reacts with ozone to form chlorine monoxide and oxygen, and then the chlorine monoxide reacts with another oxygen atom to release chlorine again and produce more oxygen. This means one chlorine atom can convert many ozone molecules into regular oxygen, thinning the ozone layer that blocks harmful UV radiation. The other substances listed—methane, water vapor, and nitrogen—affect atmospheric chemistry in various ways, but they do not drive the primary depletion of the ozone layer in the same direct, catalytic way as chlorine from CFCs.