Depletion of the ozone layer: introduction

The environmental theme 'Depletion of the ozone layer' concerns ozone in the stratosphere. This layer, about 15 to 30 kilometres high, naturally contains relatively high concentrations of ozone. This ozone prevents high levels of ultraviolet (UV) radiation reaching the earth.

There has been a fall in the amount of ozone in the stratosphere. The resulting increase in UV radiation can have numerous short-term and long-term health effects on people. It also has an impact on the natural environment (both on land and in water) and the food chain.

Depletion of the ozone layer

Nitrogen, chlorine and bromine compounds reduce the concentration of ozone in the stratosphere. Most chlorine and bromine compounds entering the atmosphere since the beginning of the twentieth century have been of anthropogenic origin, consisting of chlorofluorocarbons (CFCs), halones, hydrochlorofluorocarbons (HCFCs) and methyl bromide. These substances are mainly used as coolants in refrigerators, for dry cleaning, in aerosols, as fire extinguishing agents, for foam production and for soil disinfectants (methyl bromide). Nitrous oxide (N₂O) contributes most nitrogen compounds in the stratosphere. This gas comes mainly from natural sources, but humans also bring some into the atmosphere.

Thickness of the ozone layer

Measurements have shown that, since approximately 1980, the ozone layer has become thinner. It is expected that it will be at its thinnest in about 2000, after which it may start to recover. Complete recovery will take approximately 50 years.

Relevant substances

CFC = Fully halogenated chlorofluorocarbon
HCFC = partially halogenated hydrochlorofluorocarbon
HFC = Hydrofluorocarbon
PFC = Perfluorcarbon
Halons = Hydrocarbons with one or more bromine atoms

References

• WMO (2003 in preparation). Scientific assessment of ozone depletion: 2002. World Meteorological Organization, Global Ozone Research and Monitoring Project (report no. ??), Geneva.

Relevant sections and indicators in the Environmental Data Compendium

• Depletion of the ozone layer: policy
• Ozone-depleting substances and substitutes, global use, 1980-2000
• Sales and emissions in the Netherlands of CFCs and halons, 1980-2002
• See the 'global air quality' index for data about the Guide to 'Global air quality' section and for information about the Guide to 'Global air quality' section .
• Additional risk in the Netherlands of skin cancer due to increase in UV radiation, 1980-2000

Relevant information outside of the Environmental Data Compendium

• More information about the depletion of the ozone layer can be found on the following English websites:
• UNEP, Frequently Asked Questions About the Ozone Layer and Related Environmental Effects
• EPA (Environmental Protection Agency), with information about: science of ozone depletion, the regulatory approach to protecting the ozone layer, and on alternatives to ozone-depletion substances.
• TEAP Technology and Economic Assessment Panel (TEAP) of the Montreal Protocol.
• NASA/TOMS, most recent ozone maps and data.
• NOAA, Scientific Assessment of Ozone Depletion: 1998
• ETC/ACC (European Topic Center on Air and Climate Change).