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What Is The Ozone Layer And What Causes Ozone Depletion?

the ozone layer is recovering

The Earth’s atmosphere consists of several layers, each having a major role in maintaining life on the planet.

The first layer is called troposphere and is the most important layer of the atmosphere because we live inside it.
The troposphere extends from the Earth’s surface up to a height of 8 miles (12 km).

The second layer is the stratosphere and extends from the altitude of 12 km (8 miles) up to the altitude of 31 miles (50 km).

In the upper atmosphere, there are three more layers called mesosphere, thermosphere and exosphere, and they extend from the altitude of 31 miles (50 km) up to 6250 miles (10,000 km) in the space.

What is the Ozone Layer?

The ozone layer is located in the stratosphere (the second layer of the atmosphere) between the altitudes of 9.3 and 18.6 miles (15 to 30 kilometers) above the planet, and protects the life on Earth from the dangerous ultraviolet B (UVA and UVB) radiation produced by the Sun.

This protective layer of gas contains a high concentration of ozone (O3), but also a small quantity of other stratospheric gases, and its thickness can vary during the year depending on the season and on the geographic area.

Three oxygen atoms form the ozone molecule (O3), which is a highly reactive molecule and is constantly formed and broken down in the stratosphere.

Why is The Ozone Layer Vital For The Life On Our Planet?

The Sun constantly emits several types of electromagnetic radiation, and the ozone layer is responsible for blocking the ultraviolet A (UVA) and the ultraviolet B (UVB) radiation, which can cause more damage than benefits to life on Earth.

The exposure to UVA and UVB radiation can cause skin and eye damage and also increased infections if the immune system is weakened.

During the summer when the Sun is stronger, the exposure to UV radiation causes the tanning of the skin, which is a response of the human skin to this type of radiation.

An overexposure to UV radiation can produce red skin that becomes painful and eventually can get swollen and full of blisters.

Overexposure to UV rays from the Sun can lead to premature aging

Premature aging is another effect of overexposure to UV rays.

The skin damage produced by the Sun’s UV radiation is a cumulative process that can damage the DNA of the skin cells.

The damaged skin cells will die or will repair themselves, but if the damage of the skin is too severe to be repaired, a deadly disease (skin cancer) can appear.

A long exposure to UV rays can damage your eyes.

Wearing sunglasses that provide UVA and UVB protection can save your eyes from any damage caused by the Sun’s radiation.

A long exposure to UV radiation can weaken the immune system, and the body’s natural defense against diseases (bacteria, viruses etc.) could be diminished.

What Causes Ozone Depletion?

The ozone layer depletion is caused by the human activity (75 to 85%), natural sources (15 – 20%) and volcanic eruptions (1 to 5%), and was first observed in the late 1970s by scientists.

1. Human Activity

The human activity is the main cause of the hole in the ozone layer and is produced by a few chemical substances used by us.

These substances were named ozone-depleting substances (or simply ODS) and they consists of halocarbon refrigerants, propellants, solvents and foam-blowing agents (chlorofluorocarbon (CFCs), hydrochlorofluorocarbons (HCFCs), halons and freons).

When the CFC molecules (commonly used in refrigerators and air conditioners) reach the atmosphere, they start floating towards the ozone layer in the stratosphere.

Once there, they enter in contact with the UV radiation produced by the Sun, which leads to the release of one chlorine atom.

The free chlorine atom (Cl) will react with an ozone molecule (O3) and will produce one chlorine monoxide molecule (C10) and one molecule of oxygen (O2).

After that, a single oxygen atom (O) will react with the chlorine monoxide molecule (C10) and will produce one oxygen molecule (O2) and one chlorine atom (Cl).

The chlorine atom (Cl) will continue the cycle and will further destroy the ozone layer.

Bromine produced from methyl bromide and halons is considered much more destructive than chlorine.

2. Natural sources

There are also natural sources that can contribute to the depletion of the ozone layer.

A common natural source that causes ozone damage is the naturally occurring chlorine.

3. Volcanic eruptions

Volcanoes can damage the ozone layer when they erupt.

During a volcanic eruption, chlorine is a component of the hydrochloric acid that is released directly into the stratosphere along with sulphur dioxide.

Sulphur dioxide is more harmful than chlorine because is turned into sulphuric acid aerosols.

The sulphuric acid aerosols accelerate the damaging chemical reactions, which will make chlorine to destroy the ozone layer even faster.

The hole in the ozone layer allows the UV rays to reach the surface of the Earth, which can cause skin disease (skin cancer), eye disease, and also can increase the number infections due to a weaken immune system.

Animals and plants can be also affected by the fact that the UV rays reach the planet’s surface due to the hole in the ozone layer created by the chemical substances used by humans.

Areas of Ozone Layer Depletion

The Antarctic region was the most affected by the ozone layer depletion mostly due to the low temperatures that have accelerated the conversion of CFCs to chlorine.

In the southern area, the ozone layer is affected by the increased presence of the Sun during the day in the spring and summer seasons, which makes the chlorine to react with the ultraviolet rays and destroy the ozone layer on a massive scale.

Almost all the CFCs that are currently in the atmosphere were emitted in the Northern Hemisphere by the industrialized countries from Europe and the U.S.

International Agreements Signed to Protect the Ozone Layer

The Vienna Convention for the Protection of the Ozone Layer was one of the most important environmental agreements ever signed, and was ratified by 197 states at the Vienna Conference of 1985, and entered into force in 1988.

The Montreal Protocol on Substances that Deplete the Ozone Layer was another environmental agreement signed on September 16, 1987, and entered into force in 1989.

The purpose of the agreement was to phase-out the production of numerous substances such as: CFCs, halons, and other chemicals that are responsible for ozone-depletion.

Since 1989, the Montreal Protocol has suffered eight revisions in London (1990), Nairobi (1991), Copenhagen (1992), Bangkok (1993), Vienna (1995), Montreal (1997), Australia (1998), Beijing (1999), and Kigali, Rwanda (2016).

Due to the ban imposed on the production of chemicals responsible for ozone depletion, the ozone levels in the stratosphere have been stabilized by mid-1990s and began to recover in the 2000s.

The ozone layer is expected to reach its pre-1980 levels by the year 2075.

What Can We Do To Stop Ozone Depletion?

Human activity is the main cause of ozone depletion, and to stop this destructive process, we need to take some measures that will also limit the level of air pollution produced on the planet.

1. Find a green alternative to pesticides

Pesticides are used worldwide to get rid of weeds, but they can also harm the ozone layer.

Weeds can be removed manually (healthy physical work) and this way you can avoid the use of pesticides.

2. Use natural cleaning products

Household cleaning products usually contain toxic chemicals that can damage the ozone layer, so try to use cleaning products that contain natural ingredients.

3. Use your car less often

The large number of vehicles on the streets increases the level of air pollution in the cities, and some chemicals present in the smog can affect the ozone layer, so by reducing the number of vehicles with internal combustion engines on streets we can also avoid the destruction of the ozone layer.

Car pooling, public transportation, using a bicycle or simply walking, all these activities can replace your car and can reduce the number of vehicles on the streets, the number of traffic jams, and the level of pollution in the atmosphere.

4. Avoid using nitrous oxide and support the ban of this dangerous chemical compound

The Montreal Protocol on Substances that Deplete the Ozone Layer was signed on September 16, 1987, and entered into force in 1989, but failed to ban the use of the nitrous oxide (laughing gas) even if it is known as a big destroyer of the ozone layer.

Nitrous oxide is a greenhouse gas (produces global warming), and in terms of ozone depletion is considered more destructive than the CFCs.


The ozone layer seems to be more fragile that we thought, but way more important for the life on planet Earth.

The protection of the environment must also include the protection of the ozone layer because without it, our life here on the planet would become a nightmare.

Article written by:

I write about the renewable energy sector, electric cars and climate change issues. I love nature and good food, so I travel all over the world to see new places and meet new people. Magda Savin

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