Mentors Comment:
The answer should begin by briefly explaining the phenomenon of ozone hole.
Thereafter, students
should enumerate the specific conditions, which exist at the south pole which aid the formation of ozone
hole.
Finally the students should separately list out the health and the environmental impacts of ozone
depletion.

Answer:

Even though general understanding is that the ozone hole should be established over the regions where CFCs are released in large amounts, the reality is much different. The severe depletion of the Antarctic ozone layer known as the “ozone hole” occurs because of the special atmospheric and chemical conditions that exist there and nowhere else on the globe.

The very low winter temperatures in the Antarctic stratosphere cause polar stratospheric clouds (PSCs) to form. Special reactions that occur on PSCs, combined with the relative isolation of polar stratospheric air, allow chlorine and bromine reactions to produce the ozone hole in Antarctic springtime.

Stratospheric temperatures are lowest in both polar regions in winter. In the Antarctic winter, minimum daily temperatures are generally much lower and less variable than in the Arctic winter. Antarctic temperatures also remain below the PSC formation temperature for much longer periods during winter.

Also, PSCs exist in larger regions and for longer time periods in the Antarctic than the Arctic Isolated conditions: Stratospheric air in the polar regions is relatively isolated from other stratospheric regions for long periods in the winter months. The isolation comes about because of strong winds that encircle the poles, forming a polar vortex, which prevents substantial motion of air into or out of the polar stratosphere. This circulation strengthens in winter as stratospheric temperatures decrease, with the result that the isolation of air in the vortex is much more effective in the Antarctic than the Arctic.

Stratospheric ozone filters out most of the sun’s potentially harmful shortwave ultraviolet (UV) radiation. If this ozone becomes depleted, then more UV rays will reach the earth. Exposure to higher amounts of UV radiation could have serious impacts on human beings, animals and plants, such as the following:

Harm to human health :
• More skin cancers, sunburns and premature aging of the skin.
• More cataracts, blindness and other eye diseases: UV radiation can damage several parts of the eye, including the lens, cornea, retina and conjunctiva.
• Weakening of the human immune system (immunosuppression). Early findings suggest that too much UV radiation can suppress the human immune system, which may play a role in the development of skin cancer.

Adverse impacts on environment:
• Species of marine animals in their developmental stage (e.g. young fish, shrimp larvae and crab larvae) have been threatened in recent years by the increased UV radiation under the Antarctic ozone hole.
• Loss of biodiversity in our oceans, rivers and lakes could reduce fish yields
• In the animal kingdom, many species of animals have been found suffering from growing sunburn as a result of increased UV light.
• Wood, plastic, rubber, fabrics and many construction materials are degraded by UV radiation. The economic impact of replacing and/or protecting materials could be significant.