Ozone Layer

What is the ozone layer?

The ozone layer, as the name implies, is a layer of ozone gas (O₃) located in planet Earth’s atmosphere, occupying the area between 10 and 50 kilometers above Earth’s surface.

The ozone layer contains 90% of the ozone that exists in the Earth’s atmosphere, and it absorbs almost 100% of the high-frequency ultraviolet radiation coming from the Sun, enabling terrestrial life as we know it.

What does the ozone layer do?

The ozone layer forms a protective shield that absorbs much of the ultraviolet (UV) rays of solar radiation, letting mostly only visible light through.

The ozone layer is important because UV rays can have a lot of negative effects on terrestrial life. Some of these include:

• Altering the DNA of living beings, causing genetic mutations that can lead to countless health problems.
• Skin lesions, such as burns, premature aging, and increased risk of skin cancer.
• Reduced photosynthesis in plants due to the deterioration of chlorophyll molecules. This can have negative consequences on ecosystem balance.
• Imbalances in marine life. Like terrestrial life, UV radiation can also have harmful effects on life underwater (DNA damage, reproduction problems, reduction of photosynthesis in marine organisms, etc.).

What are the main risks to the ozone layer?

During the 1970s, the ozone layer underwent significant losses in density due to chlorofluorocarbon (CFC) compounds generated by various human activities, especially those related to aerosols and refrigeration. CFCs released into the atmosphere decompose and release chlorine atoms which, in turn, destroys the ozone molecules.

This phenomenon is called the ozone layer hole, and it has been a cause for concern ever since.

Other chemical compounds that deteriorate the ozone layer are:

• Halons: these contain bromine, chlorine, and fluorine, and they are used as fire extinguishing agents. However, they have been progressively replaced by more sustainable alternatives.
• Hydrochlorofluorocarbons (HCFCs): these contain chlorine, fluorine, and hydrogen, and they are used as refrigerants and as foaming agents in the production of plastics and insulators.
• Carbon tetrachloride (CCl4): it contains chlorine and carbon, and it is used in the production of refrigerants and solvents, among others.
• Methyl chloroform (CH3CCl3): it contains carbon, hydrogen, and chlorine. It is used as a solvent and as a cleaner in the electronics industry.
• Very short-lived halocarbons (VSLS): they contain chlorine and bromine. While they have a short life in the atmosphere (usually less than 6 months), they have a high capacity to degrade ozone. They are used to manufacture solvents, cleaning products, refrigerants, and aerosol propellants.

What measures have been taken to protect the ozone layer?

In 1987, faced with the alarming growth of the ozone hole, the Montreal Protocol was implemented in more than 190 countries. The protocol stipulated the phase-out of CFCs and other chemical compounds harmful to the ozone layer.

Since then, research on the composition and dynamics of the ozone layer has been carried out to develop effective recovery strategies. There has also been great importance given to monitoring its thickness and distribution around the planet.

The need to eliminate chemical compounds harmful to the ozone layer has led to the development of alternative technologies in different sectors, such as refrigeration, industry, and aerosols. This has allowed human activities to continue reducing their negative impact on this layer.

Education and awareness-raising have been instrumental in fostering international cooperation and commitment from different actors to protect the ozone layer. Disseminating information about the effects of the depletion of the ozone layer and the risks of exposure to UV radiation have motivated people to reduce their impact. On the other hand, changing consumption habits is the final incentive for companies to modify their products and processes.

Thanks to the combination of this set of factors, ozone levels stabilized during the 1990s, and in the 2000s, the deterioration process began to reverse. Today the ozone layer is almost restored, and scientific studies suggest that it will be completely regenerated in a couple of decades.

The protection of the ozone layer is directly related to four of the Sustainable Development Goals (SDGs) established by the United Nations for the year 2030:

• SDG 13: Climate action.
• SDG 12: Responsible production and consumption.
• SDG 14: Life below water.
• SDG 15: Life on land