Why are ozone-depleting substances phase-out substances?
These substances may pose a danger to the structure or function of the ozone layer of the stratosphere.
In the stratosphere, sunlight constantly converts some of the oxygen molecules in the air to ozone. This ozone layer filters out harmful ultraviolet radiation from the sun. Ultraviolet radiation can cause harm to health, e.g. skin cancer, cataracts and impaired immunological defence, as well as damage in the environment and to technical materials. If the ozone layer is weakened to the extent that the ultraviolet sunlight at the earth's surface increases noticeably, plant life may be damaged. Plankton algae, which play a key role in the ecosystem of seas and lakes, lack the outer, protective cell layers that are present in higher plants and are therefore even more sensitive.
The threat to the ozone layer is emissions of ozone-depleting substances such as CFCs, HCFCs, halons, chlorinated solvents, methyl bromide and similar substances. It is the chlorine or bromine content of these substances that breaks down the ozone in the stratosphere. Emissions of nitrogen oxides and other pollutants from high-altitude aircraft also have effects on the ozone layer.
The new use of CFCs and HCFCs, halons, chlorinated solvents and methyl bromide has decreased sharply or ceased altogether in Sweden. The threats to a protective ozone layer are firstly continued production and use of ozone-depleting substances in other countries and secondly emissions from high-altitude aircraft.
Read more about the environmental quality objective "A Protective Ozone Layer" and the background to this on the Swedish Environmental Protection Agency website.