What causes stratospheric ozone depletion?

• A. Anthropogenic factors such as chlorofluorocarbons and natural ice crystals in the atmosphere
• B. High-altitude volcanic eruptions exclusively
• C. Decrease in atmospheric humidity
• D. Increased solar flares

Answer: (A)

Ozone depletion in the stratosphere is driven mainly by chlorine and bromine released from human-made compounds. When chlorofluorocarbons rise into the upper atmosphere, they are broken apart by UV light, freeing chlorine and bromine atoms that catalytically destroy ozone molecules in cycles that can destroy many O3 each. A crucial part of this process involves polar stratospheric clouds formed on ice crystals in very cold conditions. These clouds convert chlorine from stable forms into reactive forms that, when sunlight returns, release chlorine radicals to keep attacking ozone, producing the ozone holes seen in polar regions.

That’s why the option highlighting anthropogenic chlorofluorocarbons is the best choice. Other factors like volcanic eruptions, humidity changes, or solar flares can influence ozone levels in some contexts but are not the primary cause of stratospheric ozone depletion.