Q.Why does ozone hole form over Antarctica? How will enhanced ultraviolet radiation affect us?

Why the ozone hole forms over Antarctica

• During the extremely cold, dark Antarctic winter, temperatures in the stratosphere fall low enough for polar stratospheric clouds (PSCs) to form from ice crystals.
• The surfaces of these ice crystals provide sites for chemical reactions that convert relatively inert chlorine "reservoir" compounds (derived from CFCs released by human activity) into reactive chlorine species such as Cl and ClO.
• A polar vortex — a strong, isolated circulation of air — traps this air mass over Antarctica through the winter, preventing it from mixing with ozone-rich air from lower latitudes.
• When sunlight returns with the onset of spring, it drives photochemical reactions that release chlorine atoms from these reactive compounds. Each chlorine atom then acts as a catalyst, breaking down thousands of ozone (O3) molecules into oxygen in a rapid chain reaction, without itself being consumed.
• The combination of high reactive-chlorine concentration and the isolating polar vortex causes a dramatic, localised thinning of the ozone layer each spring — the "ozone hole."

Effects of enhanced ultraviolet (UV-B) radiation on us

With the protective ozone layer thinned, more UV-B radiation reaches the Earth's surface, which:

• Damages DNA, causing mutations that increase the risk of skin cancers, including melanoma.
• Causes cataracts and other eye damage, and can lead to snow-blindness.
• Ages the skin prematurely and can suppress the immune system, increasing susceptibility to infections. …

Explain the ozone-hole formation as a sequence: extreme cold → polar stratospheric clouds → conversion of chlorine reservoir compounds to reactive chlorine → polar vortex isolation → spring sunlight triggers catalytic ozone destruction. Then …

• Saying CFCs "directly" destroy ozone without explaining the two-step mechanism — reservoir compounds must first be converted to reactive chlorine on polar stratospheric cloud surfaces, and destruction is triggered by the return of sunlight.
• Forgetting the role of the polar vortex in isolating and concentrating the effect specifically over Antarctica (rather than uniformly across the globe). …