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Annual mean atmospheric concentrations of ozone depleting substances, including chlorofluorocarbons (e.g. CFC-11, CFC-12 and CFC-113 etc), hydrochlorofluorocarbons (e.g. HCFC-21 and HCFC-22 etc), halons (e.g. Halon-1211 etc), methyl chloroform, carbon tetrachloride, and methyl bromide. It is now well established that the depletion of stratospheric ozone is linked to the presence of reactive chlorine and bromine, transported from the surface in the form of CFCs, chlorinated solvents and halons. These ozone depleting substances (ODSs) have very long lifetimes in the atmosphere. Under the Montreal Protocol, CFCs and other ODSs are being phased out as quickly as possible. To expedite this process, the chemical industries have developed replacement gases. In the short term, hydrochlorofluorocarbons (HCFCs) are replacing the CFCs. However, the HCFCs still contain chlorine, and so they will eventually be replaced by hydrofluorocarbons (HFCs) and other non-ozone depleting substances.
ANZECC Core Indicator A6 (ANZECC 2000) |
