ozone depleting chemicals

The ozone layer is about 10-50 km above the earth, and protects us from harmful UV radiation, which can cause skin damage. UVB is also harmful to some freshwater and marine life, which are vital components of the food chain.

In 1994 the 'ozone hole' above the Antarctic was measured at 24 million km square (about three times the size of Australia!). This has been caused by chemicals which break down ozone, known as ozone depleting chemicals (ODCs).

Chlorofluorocarbons (CFCs) are the main ODCs. Introduced in the 1920s, CFCs have been widely used in refrigeration, plastic foams and aerosols. UV radiation breaks down CFCs in the Stratosphere, releasing chlorine, which acts as a catalyst in the breakdown of ozone. The effects of CFCs will last for over a century, making this a problem that is unlikely to go away in most people's lifetimes.

Other ODCs include:

• Hydrocholorofluorocarbons (HCFCs) - used in domestic refrigerators
• Hydrobromoflourocarbons (HBFCs) - used as fumigants and in fire extinguishes
• Sulphur dioxide - can also occur naturally from volcanic eruptions
• Nitrogen oxides - from aircraft vapours, fertilisers, and the burning of fossil fuels

Each ODC varies in the extent in which it effects the ozone layer, and is represented by a number called the ozone depleting potential (ODP). Most developed countries have phased out the use of ODCs concentrating first on those with the highest ODPs. However, many developing countries still use ODCs, especially in agriculture because they are cheaper.

In the UK, a number of pieces of legislation have been introduced which aim to control the use of ODCs, initiated by the Montreal Protocol on Substances that Deplete the Ozone Layer 1987.

The latest ODC EC regulations (2037/2000) were introduced in June 2000. Since January 2002 it has been illegal to dispose of domestic fridges and freezers without first capturing and destroying the ODCs contained within them. Around three million fridges and freezers are scrapped in the UK every year and there are currently various proposals under discussion as to the best way to manage these. For the latest information, click here.