What really causes the ozone layer to deteriorate?

Question

What really causes the ozone layer to deteriorate?

Answer 1

For a while, it was chlorofluorocarbons (CFCs).  But now CFCs have been banned and it is thought that the ozone layer will slowly repair itself.

I don't know how much you know about the ozone layer, so forgive me if this answer explains things you already know.  Oxygen gas, the kind we need to breathe, is made of two oxygen atoms per molecule; hence, its molecular formula is O2.  When oxygen gas interacts with ultraviolet radiation, it is converted to a three-atom molecule called ozone, O3.  Unlike O2, we cannot live off of O3; in fact, it is poisonous to us.  In the stratosphere, however, it is beneficial.  O3 absorbs ultraviolet light (the same kind of light that created it in the first place), and keeps it from reaching the surface of the Earth.  That makes it safe for us to live on land.  Without the ozone layer, we would very quickly all become blind and cancer-ridden.  (In fact, the formation of the ozone layer hundreds of millions of years ago was one of the major factors that allowed life to move onto land from the water in the first place).

CFCs are molecules that contain (surprise!) chlorine.  They used to be contained in lots of products, including aerosol cans.  When they were released into the atmosphere, they mixed with other gases and were eventually borne aloft to the ozone layer.  At that height, the increased UV radiation caused the gas molecules to dissociate.  Extremely-reactive chlorine atoms were split off from the CFC molecules.  These molecules acted to catalyze the conversion of ozone to O2.  Did I mention that O2, unlike ozone, doesn't absorb UV light very well?  Well, it doesn't.  The wholesale destruction of stratospheric ozone could therefore have very serious consequences for life on land.

The problem is deeper than that.  Chlorine doesn't just change ONE ozone molecule to oxygen.  Because the chlorine atom is unchanged by the reaction, it survives to change yet another ozone molecule, then another, then another.  In fact, every chlorine atom released into the ozone layer can catalyze the conversion of 100,000 ozone molecules to oxygen.  Clearly, the problem could get out of hand quickly.

The Montreal Protocol banned the production of CFCs as well as other ozone-depleting chemicals.  There is cautious optimism that the ozone layer can repair itself within the next few decades.  I certainly hope so...we need some good news.

I hope that helps.  Good luck!

Answer 2

aerosols and CFCs (chlorofluorocarbons)

some aerosols occur naturally, but most of the more harmful ones are created by man.  one CFC molecule can destroy up to 100,000 Ozone molecules.