Asked by: Rob Munton, Poole
The main ozone-depleting gases are chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). The Montreal Protocol, which came into force in 1989, lists 56 CFCs and 34 HCFCs, and production of almost all of them is now completely banned. There are a few exceptions where there isn’t an alternative, such as the fire suppression systems on submarines.
However, a study at the University of East Anglia found three new CFCs and one HCFC that have recently been released into the atmosphere. The amounts aren’t large – less than one per cent of the total release of ozone-depleting compounds before the Montreal Protocol was signed. But the source of these new compounds is currently unknown and the levels of two of them are rising rapidly. These chemicals will also take several decades to break down naturally, so they will continue to be a problem, even if their production is stopped immediately.