1.   The polar regions are particularly at risk because the chemical reaction that destroys ozone is helped by their weather conditions.

2.   Today there is general agreement that ozone is destroyed by chlorine.

3.   The only significant break-down of the gas occurs in the stratosphere, where, like other man made gases, it catalytically destroys ozone.

4.   This would remove chlorine from the chain of reactions which destroys ozone.

5.   This ejected fine dust and ash particles into the atmosphere, which are believed to be accelerating the chemical reactions by which ozone is destroyed by chlorine compounds.

6.   Artificial chemicals known as chlorofluorocarbons, or CFCs, once ubiquitous in aerosol spray cans and air-conditioner coolant, cause a chain of reactions that destroy ozone.

7.   However, the chemical is known to destroy ozone when it evaporates from the soil and floats to the stratosphere.

8.   Industrial chemicals, principally chlorofluorocarbons used as refrigerants, destroy stratospheric ozone.

9.   No more chlorofluorocarbons, the refrigerants that can destroy protective ozone in the atmosphere.