Ozone Depletion

In the 1970s, scientists started studying the effects of various substances on the atmosphere, particularly chemicals called chlorofluorocarbons, or CFCs. These compounds were used as aerosol sprays and as refrigerants in freezers and car air conditioners.

They found that these widely used substances were very stable and hard to breakdown. Because of this, CFCs are often swept into the upper part of our atmosphere by winds, and this is where the problems begin.

The upper ten or twelve miles of our atmosphere, called the stratosphere, contains the majority of a compound called ozone. It consists of three oxygen atoms, whereas the oxygen we breathe has only two. Ozone serves a very valuable purpose ... it protects us from radiation, UVB radiation to be precise.

Hole in the ozone layer (blue/black area), as seen from satellite picture above the earth's South pole.  Hole size is 10.5 million square miles.

This type of radiation has been shown to cause the following:

  •     some types of skin cancer
  •     cataracts
  •    a reduction in crop yield
  •    disruption of marine ecosystems


Ozone protects us from radiation because it absorbs it. In other words, radiation destroys the ozone instead of harming us. However, ozone forms naturally at a rate equal to its destruction by the sun's harmful rays. Normally, the amount of ozone in the stratosphere stays relatively constant even though it is continuously being broken down and reformed. However, CFCs chemically speed up the conversion of ozone to oxygen. 

When CFC's reach the stratosphere, the strong radiation from the sun causes the release chlorine atoms. Each chlorine atom can breakdown thousands and thousands ozone molecule. So, how does this affect the natural balance of ozone in the stratosphere? It severely reduces ozone, at a much higher rate than can be corrected by the regular processes of ozone formation. Think of it as a bucket with a hole in it that is too large to keep the bucket full by adding water.


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