asked the Secretary of State for the Environment if he will list, in order of importance, the five chemical compounds which on current usage patterns within the United Kingdom has the greatest ozone-depleting potential.

Depletion of the ozone layer is a global problem. It is generally accepted internationally that the five chemical compounds having the greatest ozone-depleting potential are CFC 12, CFC 11, CFC 113 and Halons 1211 and 1301, having regard to the relative efficiency of subtstances to destroy ozone and estimates of global production. Figures for the use of these chemicals in the United Kingdom are not available.