Protection of the ozone layer

The ozone layer is a layer of gas in the upper atmosphere which protects humans and other living things from the harmful ultraviolet (UV) rays of the sun. Although ozone (O3) is present in small concentrations throughout the atmosphere, most ozone (about 90%) exists in the stratosphere, in a layer between 10 and 50km above the surface of the earth. This ozone layer performs the essential task of filtering out most of the sun's biologically harmful UV radiation. Concentrations of ozone in the atmosphere vary naturally according to temperature, weather, latitude and altitude. Furthermore, aerosols and other particles ejected by natural events such as volcanic eruptions can have measurable impacts on ozone levels.

Concentrations of ozone in the atmosphere vary naturally according to temperature, weather, latitude and altitude. Furthermore, aerosols and other particles ejected by natural events such as volcanic eruptions can have measurable impacts on ozone levels.  However, the current levels of ozone depletion cannot be explained with natural phenomena.

The scientific evidence shows that certain human-made chemicals are responsible for the creation of the Antarctic ozone hole and the global ozone losses. Ozone Depleting Substances (ODS) have been used in many products which take advantage of their physical properties (e.g. chlorofluorocarbons (CFCs) have been used as aerosol propellants and refrigerants).

ODS are broken down by sunlight in the stratosphere, producing halogen (e.g. chlorine or bromine) atoms, which subsequently destroy ozone through a complex catalytic cycle. Ozone destruction is greatest at the South pole where very low stratospheric temperatures in winter create polar stratospheric clouds. Ice crystals formed in these clouds provide a large surface area for chemical reactions, accelerating catalytic cycles. The destruction of ozone also involves sunlight, so the process intensifies during spring time, when the levels of solar radiation at the pole are highest, and polar stratospheric clouds are continually present.

Source: NASA

While ozone levels vary seasonally, overall stratospheric ozone levels have been decreasing since the 1970s. Mid-latitudes have experienced greater losses than equatorial regions. In October 2006 the largest Antarctic ozone hole observed to date covered 27 million km2.

Although ozone losses are less radical in the northern hemisphere significant thinning of the ozone layer was also observed over Europe. Over the Arctic the ozone loss in the winter 2004/2005 was among the largest ever diagnosed and significant ozone loss was also observed over Europe.

Increased UV levels at the earth's surface are damaging to human health. The negative effects include increases in the incidence of certain types of skin cancers, eye cataracts and immune deficiency disorders. Increased penetration of UV results in additional production of ground level ozone, which causes respiratory illnesses.

Biologically, UV affects terrestrial and aquatic ecosystems, altering growth, food chains and biochemical cycles. In particular, aquatic life occurring just below the surface of the water, where plant species forming the basis of the food chain are most abundant, are adversely affected by elevated levels of UV radiation. Depletion of stratospheric ozone also alters the temperature distribution in the atmosphere resulting in indeterminate environmental and climatic impacts.

There are a number of direct and indirect negative economic effects that are linked to ozone depletion and the increase of UV radiation.

Increased health costs are the most important direct economic impact of increased UV radiation. The medical expenses for millions of additional cases of skin cancers and eye cataracts pose a threat, in particular in less developed economies. Furthermore, an increased UV radiation reduces the lifetime and tensile properties of certain plastics and fibers.

Indirect economic impacts include the additional costs for example caused by the reduced availability of fish stocks, or the mitigation to climate change.

Despite existing regulation of ODS, there continues to be severe ozone depletion. This is because once released ODS stay in the atmosphere for many years continuously causing damage. However, since less and less ODS are emitted, the first signs of recovery of the ozone layer are visible. Nevertheless, because of the long lifetime of ODS, and unless additional measures are taken, the ozone layer is unlikely to recover before the mid of the century.

You have already taken the first steps to help protect the ozone layer by informing yourself of the problem and its causes. Try to find out as much as you can about the problem from publications, schools, the internet or public libraries. The only way to mend the ozone hole is to stop the release of ODS into the atmosphere. However, there are a number of practical initiatives which can be taken at the individual level to help protect the ozone layer:

• Make sure that old refrigerators and air conditioners are disposed off safely by giving it to a recycling yard without damaging the cooling circuit
• Ensure technicians repairing your refrigerator or air conditioner recover and recycle the old ODS so they are not released into the atmosphere.
• When renovating your house make sure that old insulation foams containing ODS are disposed of as environmentally hazardous waste
• Suggest school activities to increase awareness of the problem and to initiate local action.

There is a direct link between increased exposure to UV radiation and elevated risk of contracting certain types of skin cancers. Risk factors include skin type, sunburn during childhood, and exposure to intense sunlight. Recent changes in lifestyle, with more people going on holiday and deliberately increasing their exposure to strong sunlight, are partly responsible for an increase in malignant skin cancers. In order to minimise the risk of contracting skin cancer, cover exposed skin with clothing or with a suitable sunscreen or sun cream, wear a hat, and wear UV-certified sunglasses to protect the eyes.

While an increased amount of UV radiation is bad for human health, also an underexposure can have negative effects. Those are mainly related to the reduced vitamin D production in the skin which is induced by UV radiation. Under-supply of vitamin D is the cause of a number of illnesses such as osteoporosis, osteomalacia, rickets or cardiovascular problems. Dark skinned people are particular vulnerable against a decrease of natural UV radiation. However, most people are sufficiently exposed to UV radiation every day. There is no medical reason to seek additional exposure for healthy humans.