A3.8 Anthropogenic Influences on Ozone Depletion


Observations since the 1960s have shown that total global ozone levels have decreased by 1-2% from the maximum to the minimum of a typical cycle. However, since downward trends in ozone levels are much larger than 1-2%, particularly at the higher latitudes, the Sun’s output cannot be wholly responsible.

Man-made influences predominantly relate the manufacture and use of Ozone Depleting Substances.

Ozone Depleting Substances Include:

  • Chlorofluorocarbons (CFCs) – used in refrigeration, air conditioning, and fire extinguishers.

Chlorofluorocarbons (CFCs) are a group of compounds. For example, it includes:

  • Trichlorofluoromethane (CCl3F)
  • Dichlorodifluoromethane (CCl2F2)
  • Monochloropentafluoroethane (C2F5Cl)
  • Tetrachlorotetrafluoropropane (C3F4Cl4)


  • Hydrochlorofluorcarbons (HCFCs) – man made compounds not found naturally, used to replace CFCs in refrigeration, aerosol propellants, foam manufacture and air conditioning.


  • Halons – used in fire extinguishers.

Halons include:

  • Bromochlorodifluoromethane (CF2ClBr)
  • Bromotrifluoromethane (CF3Br)


  • Methyl Chloroform also known as (1,1,1-trichloroethane) – used as an all-purpose industrial solvent.


  • Carbon Tetrachloride (the main precursor of CFCs) (CCl4) – used as in fire extinguishers, an industrial solvent and as an agricultural fumigant.


  • Methyl Bromide (CH3Br) – used as a pesticide.