University of Bristol
Wellcome Trust
Recommended by:
Society of Biology
PEEP for Physics & Ethics at GCSE


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CFC’s and the Ozone Layer

Are there holes?

  • Measuring ozone holes: In 1984 the problem of ozone depletion was first detected. Researchers in Antarctica noticed thinning in the spring and early summer (September –December).
  • It is more a ‘thinning’ than a hole. In some areas, there was a decrease of more than 50%.
  • In 1999, the hole was at its largest.
  • Between 1999-2000 (winter) there was a depletion of 65% compared to about 45% the previous winter.
  • Ozone loss is expected to decrease (due to the banning of gases which damage the layer) until around 2050. This will equal the 1975 level.
  • It will take 100-200 years for full recovery to pre-1950 levels.
  • Ozone levels are measured using satellites. U.V. thickness is measured in Dobson Units (DU). Visit the following webpage to see ozone levels in recent months. For a comparison, tropical ozone levels are between 250-300 DU throughout the year.
  •  Click here for more information on Dobson Units

Ozone holes or thinning areas –are they dangerous?

Ozone holes or thinning areas have a number of effects:

  • On human health: One estimate suggested that a 2.5% reduction in the layer would cause 0.8 million cancer deaths and 40,000,000 additional cases of skin cancer.
    For more detail  click here
  • On plants: productivity of some plants like soya bean (an important crop producing high levels of protein). It can also make plants more susceptible to disease.
  • On Marine Ecosystems: one study highlighted the harmful effects on phytoplankton (green plankton). This could disrupt food chains. In marginal ice zone, there has been a 6-12% reduction.
  • On cycles: the carbon cycle is being altered due to less carbon dioxide being absorbed by plants. This might contribute to global warming.
  • On Materials: synthetic polymers are broken down by UVB radiation. This may reduce the lifespan of ‘polymers’ in outside conditions e.g. window frames. Additives can be used to reduce this effect.
  • For more detail  click here

Causes of damage to the ozone layer.

  • The main cause of ozone depletion is the release of a group of gases known as CFC’s (chlorofluorocarbons).
  • These are used as refrigerator coolants, in aerosols and expanded plastics.
  • The gas is man-made, inert and harmless to humans.
  • These gases slowly rise into the upper atmosphere (they may take many years to do this, so have a delayed effect), where they react with ozone.
    • CFC’s rise into the upper atmosphere
    • Chlorine is released when the CFC breaks down
    • Cl + O3 form CLO and O2
    • CLO + O form CL and O2
    • O3 is now depleted and CL is free to cause further decay of O3
  • High flying jets release sulphuric acid droplets which act as nuclei for chlorine and other pollutants which then destroy ozone.

Plugging the hole – the future

  • There are a number of ways to reduce ozone depletion and there has been considerable success since the holes were first discovered in 1984.
    1. Ban the use of CFC’s –  The Montreal Protocol
    2. Produce jet aircraft fuel with a lower sulphur content.
    3. Find safe alternatives to CFC’s.


  1. Investigate the history of Ozone Depletion:
    1.  Ozone Hole History
    2. Ozone Depletion
  2. High flying jets are said to damage the ozone layer and also contribute towards global warming. They also spread pests and diseases between continents. Investigate this claim and put a case ‘for’ or ‘against’ high level jet travel.
  3. Why does ozone thinning happen mainly in the polar regions?




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