Ozone Depletion

Man-made chemicals have damaged the ozone layer that protects the earth from ultra violet (UV) radiation. We have phased out many ozone destroying chemicals but we’re still unsure how and when the ozone layer will recover.

What is ozone?
Ozone is a gas made of oxygen atoms. It can be found at ground level where it is a pollutant and a health hazard. But the useful ozone in the upper atmosphere, known as the ozone layer, is being destroyed. Here, ozone absorbs some of the potentially harmful ultraviolet radiation from the sun.

Which chemicals damage the ozone layer?
A group of chemicals known as halocarbons destroy ozone. The most familiar of these are chlorofluorocarbons (CFCs).
Aerosols and old refrigerators have released CFCs into the atmosphere. UV radiation breaks down CFCs in the upper stratosphere, releasing chlorine. Once released, chlorine becomes a catalyst of ozone destruction. A catalyst is something that makes a chemical reaction happen more easily, but it remains unchanged or reforms by the end of the reaction. It can then take part in the reaction again.
During this process, the ozone molecule is destroyed while the chlorine catalyst reforms. A single chlorine atom in the stratosphere can destroy about 100,000 ozone molecules.
The chemicals released into the upper atmosphere destroy ozone. However, pollution at ground level creates ozone, which can also affect life

How much of the ozone layer has been damaged?
In the past 30 years the ozone holes over the north and south poles have grown and shrunk.It was first suggested in 1974 that CFCs might damage the ozone layer. Scientists discovered a hole in the ozone layer over Antarctica in 1985. In September 2000, the ozone hole reached a record size of 30 million km2 - larger than North America. In September 2002, the ozone hole was just 15 million km2 - the smallest it has been since 1988.

Does the ozone layer damage affect the UK?
Yes. Ozone layer damage extends from the Arctic to northern Europe, including the UK. At Camborne in Cornwall and Lerwick in the Shetland Islands, total ozone concentrations have generally fallen since 1979 (suggesting ozone loss), although there has been an increase in recent years (Figure 1).
What are the effects of ozone loss?Declining ozone values mean UV levels have increased over the UK. UV exposure stops our immune systems working properly. We can develop eye cataracts and skin cancers. Deaths in England and Wales from malignant skin melanomas rose from 200 to 300 per year in the early 1950s to to 2167 in 2008.
UV radiation may also damage plants, and the young stages of aquatic wildlife.
What is being done to stop ozone layer damage? Industrialised countries have agreed to phase out halocarbons. Some critical uses are exempt and developing countries have been given longer time-scales. The UK did not stop CFC production until 2000.
By the late 1990s, atmospheric concentrations of other halocarbons had levelled out. Bromine concentrations should peak between 2000 and 2010, but will decline only slowly because a high proportion comes from uncontrolled sources, including the oceans.
HCFC (hydrochlorofluorocarbons) concentrations have increased from the early 1990s because they are used as a substitute for CFCs. Globally, HCFCs must be cut by 99.5% by 2020. They should begin to decline after 2010 as they are phased out. HCFCs will be banned in the European Union from 2015.
Stockpiled, recycled and illegally traded CFCs, together with those in refrigeration and fire-fighting equipment, will still be around for many years. The EU has regulations to prevent leaks of ozone depleting substances and promote recovery after use in industrial processes, although not in manufactured products.

Will ozone levels ever return to normal?
We don’t expect to see the signs of recovery in the ozone layer for 15 to 20 years. If the provisions of the Montreal Protocol on Substances that Deplete the Ozone Layer of 1987 are strengthened and followed, there is a prospect that the Antarctic ozone hole will be repaired by 2100. But greenhouse gases and changing global temperatures which are also altering the atmosphere make the nature of recovery uncertain. However, if the provisions of the Montreal Protocol are strengthened and followed, we could see the Antarctic ozone hole repaired by 2100.