Ozone hole

Why is the ozone layer important?

As a result of a prolonged exposure to (mainly ultraviolet) radiation around the globe, a coating of air has formed which contains an elevated amount of ozone. This coating has been named the ozonosphere, but it is called the ozone layer just as often. It stretches from 10 to 60 kilometres. The ozone layer works as a natural, protective filter. UV radiation reaching the Earth consists of three main components:

• UV-A: accounts for about 7% of solar radiation. It covers wavelengths from 315 nm to 400 nm. It poses no risk to living organisms. Sometimes UV-A radiation is mentioned as beneficial because, during sunbathing for example, it facilitates the synthesis of certain vitamins.
• UV-B: this type of radiation accounts for about 1.5% of the total solar flux. It covers wavelengths from 280 nm to 315 nm. Long-term exposure to this type of radiation can have negative consequences for living organisms, including animals and plants.
• UV-C: accounts for just 0.5% of solar radiation. UV-C radiation corresponds to wavelengths below 280 nm. This type of radiation is the most dangerous. The greatest amount of energy is delivered to the Earth with it, and it has a devastating effect on living organisms.

The ozone molecules that make up the ozone layer have the ability to absorb radiation in the range from 200 to 315 nm, so they absorb harmful UV-B and UV-C radiation but are unable to absorb UV-A radiation. Thanks to these properties, the ozonosphere and the ozone it contains protect living organisms from harmful radiation and allow them to function safely.

Causes of the ozone hole

The ozone layer surrounding the globe is very thin. Mainly due to anthropogenic activities, ozone concentration decreases in some specific areas. It is important to remember that the ozone hole is not a hole in the literal sense. Among the causes leading to the destruction of the ozonosphere, and thus to the formation of the ozone hole, are:

• Release of chemicals that cause ozone oxidation into the stratosphere. This group includes, among others, methane and hydrocarbon solvents. A characteristic feature of these substances is their low boiling point, and thus their high volatility. They enter the atmosphere in gaseous form and reach the stratosphere thanks to air movements. The vapours of these compounds then interact with the ozone and oxygen contained in the ozonosphere. As a result of these processes, ozone concentrations are depleted.
• Emissions of substances catalysing the decomposition of ozone to molecular oxygen. These compounds are particularly dangerous to the stratospheric ozone layer. Hydrocarbon derivatives containing an element from group 17 of the periodic table, i.e. halogenated hydrocarbons, are particularly aggressive. These compounds have the ability to catalytically break down large amounts of ozone, without changing the structure of their own molecule. This group primarily includes so-called CFCs and halons, which were widely used in past decades, for example as refrigerants in refrigerators. Although they have been phased out, for some 20 to 30 years we have been experiencing the consequences of the introduction of CFCs, halons and other similar compounds into the stratosphere. After reaching the stratosphere, these compounds are broken down by UV radiation, resulting in the release of chlorine, among other things. It is this element that destroys ozone.

Effects of the ozone hole on people and the environment

For several years now, global awareness of the problem of the formation and expansion of the ozone hole has been growing. So far, a number of measures have been taken to minimise the consequences of introducing huge amounts of pollution into the atmosphere. The resulting ozone depletion is already having serious consequences for people as well as the environment.

Less ozone in the stratosphere results in more UV radiation reaching the Earth, including UV-A and UV-B. Long-term exposure to them leads primarily to lesions on the skin, which is particularly susceptible to irritation and burns. Frequent exposure to sunlight can result in degenerative changes in cells, fibrous tissues and blood vessels. UV radiation can cause skin cancer, namely melanoma. In addition to skin lesions, it can also cause eye diseases, including cataracts, and a general weakening of the immune system, which translates into increased susceptibility to viral or parasitic infections.

The environment is equally vulnerable to changes caused by the depletion of the ozone layer. As a result of this phenomenon, climate change can occur, such as an increase in the Earth’s temperature, intensified desertification or increased evaporation. Like humans, animals are also prone to skin diseases. Although the vast majority of their skin is protected by fur, the exposed parts are nevertheless heavily exposed to radiation. In addition, the weakening of the overall immunity of animals may result in the extinction of certain species. Other victims of the ozone hole are plants. Their aerial parts are so delicate that aggressive UV radiation easily damages them. The disappearance of some plants from the Earth’s surface will lead to the disruption of the entire ecosystem. Among other things, plants retain moisture in the soil, and their absence will lead to further desertification and a significant reduction in crops harvested from arable fields.