Ozone Depletion

According to the Natural Resources Defense Council...

The ozone layer has been there for eons. High above our heads, a fragile, invisible layer of ozone shields the earth's surface against dangerous solar ultraviolet radiation. 

But now man is destroying this protective shield with chlorofluorocarbons (CFCs), halons, and other man-made chemicals that float up to the stratosphere, 6 to 30 miles overhead. These substances break down and release atoms that destroy the ozone. 

Source: Solar UV in Our World (2002) ACER, Environment
Canada, Health Canada  www.acer-acre.org

What are CFCs?

CFC is put to 100s of uses because chlorofluorocarbons are relatively non-toxic, non-flammable, and do not decompose easily. And because they're so stable, they will last for up to 150 years.

CFC gases rise slowly to about 25 miles where the tremendous force of the sun's ultraviolet radiation shatters the CFC, freeing a chemical element chlorine into the atmosphere.

Once freed, a single atom of chlorine destroys about 100,000 molecules of ozone before settling to the Earth's surface years later. Three percent, and perhaps up to five percent, of the global ozone layer has already been destroyed by CFCs. 

So what happens next?

As ozone diminishes in the upper atmosphere, the earth receives more ultraviolet radiation, which promotes skin cancers and cataracts, and depresses the human immune system.

Health effects will worsen, crop yields and fish population will reduce, as more ultraviolet radiation penetrates the atmosphere. It will affect the well being of every person on the planet.  

References: The Earth Works Group | The Natural Resource Defense Council | Curtis A. Moore, International Wildlife Magazine | Worldwatch Paper 87, The Worldwatch Institute