Ozone

Ozone (O3) is the triatomic form of oxygen. It is a gaseous atmospheric constituent.

The ozone layer is a layer of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It is mainly found in the lower portion of the stratosphere, from approximately 15 to 35 kilometres above Earth.

Ozone depleting substances are man-made chemicals that damage the ozone layer. They have contributed to the formation of the 'ozone hole' over the Antarctic.

The emissions of ozone depleting substances increased in the middle to late 20th century, linked to the use of chemicals such as Chlorofluorocarbons (CFCs) in refrigeration, industrial cleaning, foam blowing and air conditioning.

As a result of the threat of increased ozone depletion, an international agreement was formulated in 1987, known as the Montreal Protocol on Substances that Deplete the Ozone Layer, to reduce the worldwide use of ozone depleting substances.

For more information see: Ozone depleting substances.

NB The glossary of statistical terms, published by the Organisation for Economic Co-operation and Development (OECD), defines ground-level ozone as: ‘…ozone present as a secondary pollutant in the lower atmosphere, where its formation can be enhanced by other pollutants. It is highly toxic at levels above 0.1 parts per million (p.p.m.).’

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