Stratospheric Ozone – Causes and Effects of Ozone Depletion

Stratospheric ozone is a naturally occurring gas in the upper atmosphere (stratosphere) that filters the Sun ultraviolet (UV) radiation. Stratospheric ozone depletion allows more ultraviolet rays to reach the Earth’s surface harming the animals and plants. The ozone layer absorbs UV radiation, limiting its reach to the Earth’s surface, and also generating heat that helps regulate the atmosphere’s temperature structure. In this article, we will cover Stratospheric ozone production, depletion, ozone hole, the importance of Stratospheric ozone, and much more

What is Stratospheric Ozone?

Stratospheric ozone is a gas of three oxygen atoms naturally formed in the Stratosphere zone between 15 km to 30 km above the Earth’s surface. It absorbs the ultraviolet (UV-B) radiation coming from the sun and thus protects the living beings on the Earth’s surface from the harmful effects of UV-B radiation. Therefore, it is said stratospheric ozone is a ‘good’ ozone.

Stratospheric Ozone Production

Stratospheric Ozone is formed naturally from atmospheric oxygen by a chemical reaction in the presence of ultraviolet rays of the Sun. The stratospheric ozone production involves 2 steps –

• First Step – ultraviolet radiation of the sun breaks one oxygen molecule (O₂) into two oxygen atoms.
• Second Step – each of these highly reactive oxygen atoms combines with an oxygen molecule to produce an ozone molecule (O₃).

These reactions occur continuously in the presence of solar UV radiation in the Stratosphere resulting in the largest ozone layer formation in the tropical Stratosphere. This Stratospheric ozone production is balanced by its destruction in chemical reactions with a wide variety of natural and chemical compounds produced by humans in the Stratosphere. In each of these reactions, an ozone molecule is destroyed and other chemical compounds are produced.

Why is the Ozone Layer Important?

Stratospheric ozone plays an important role in the survival of all organisms on the Earth. The importance of Stratospheric ozone is stated below.

• The stratospheric ozone absorbs 97% to 99% of the UV-B radiation coming from the Sun.
• It protects all forms of life on the Earth’s surface from the harmful effects of UV-B radiation which can denature DNA.
• It generates heat by absorbing harmful solar radiation which helps to maintain the temperature structure of Earth’s atmosphere

What is the Ozone Hole?

The Stratospheric ozone hole is a region of exceptionally depleted ozone in the Stratosphere over the Antarctic which occurs during the beginning of spring (August – October) in the Southern Hemisphere. In the area of the ozone hole, the ozone column values amount to 220 Dobson.

Stratospheric Ozone Depletion

Stratospheric ozone depletion is directly linked to the stratosphere’s temperature. It mainly occurs over both hemispheres of the Earth where the temperature drops down below -78°C and stratospheric clouds tend to form. Moreover, ozone can be destroyed by chlorine and bromine more quickly than it is naturally created.

One chlorine molecule can destroy more than 100,000 ozone molecules at a time. Some compounds known as ozone-depleting substances (ODS) release chlorine or bromine which in the presence of UV radiation contribute to ozone depletion in the Stratosphere. These substances include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, methyl chloroform, halons, and methyl bromide.

Stratospheric Ozone Depletion Causes

According to the research on Stratospheric ozone depletion, the causes of ozone depletion can be categorized into two types: natural processes and anthropogenic activities.

Natural Processes

Some natural processes, such as eruptions of large volcanoes indirectly contribute to the Stratospheric ozone depletion. One study showed that in 1991 Mt. Pinatubo’s eruption produced large amounts of tiny particles called aerosols. These aerosols increase chlorine’s potential to destroy the ozone layer.

Anthropogenic Activities

• Emission of Chlorofluorocarbons (CFCs): Highly volatile CFCs used as solvents, refrigerants, foam-blowing agents, degreasing agents, aerosol propellants, and fire extinguishers (halons) are responsible for ozone layer depletion.
• Unregulated Launches of Rockets: Studies revealed that unregulated rocket launches can lead to more ozone depletion than CFCs.
• Global Warming: Global warming and the greenhouse effect also contribute to the ozone layer depletion. Due to the greenhouse effect, the heat radiated from the Earth’s surface is trapped in the Troposphere, and cannot reach the Stratosphere level. Thus, the Stratosphere remains cold and this low temperature initiates ozone depletion in the Stratosphere.
• Emission of nitrogenous compounds: Nitrogenous Compounds such as NO, N₂O, and NO₂ emitted from fossil fuel combustion, vehicles, and agricultural pesticides are considered to be greatly responsible for the depletion of the ozone layer.

What are the Effects of Stratospheric Ozone Depletion?

Stratospheric Ozone depletion adversely affects human health as well as the environment as it allows harmful UV radiation to reach the Earth’s surface. These radiations have an enormous impact on human health by causing severe diseases such as skin cancer, eye damage, genetic mutations, etc. Furthermore, ozone depletion also negatively affects aquatic life, biogeochemical cycles, and air quality and also contributes to Global warming.

Effects on human health

It causes many severe diseases which are as follows:

• Effects on eyes: UV radiation can cause severe damage to the eye lens and cornea which may lead to photokeratitis, cataracts, and blindness. It has been reported that there would be a 0.3% – 0.6% increase in the risk of cataracts with a 1% decrease in Ozone level.
• Effects on Skin: Exposure to UV radiation causes sunburns and different skin cancers such as melanoma and non-melanoma skin carcinoma.
• Effects on human immunity: UV radiation can cause changes in skin photoreceptors and antigen-presenting cells which lead to immunosuppression in cases of skin cancer, infectious diseases, and other antigens.
• DNA Damage: Short exposure to UV-B radiations can cause DNA damage. It denatures the structure of biomolecules such as lipids, proteins, and nucleic acids. UV-B radiations can cause the generation of some cryptic transposable elements which may subsequently lead to mutations which is very dangerous.
• Lung disease: Lungs are badly affected by UV radiation which can cause bronchitis, obstruction of the lungs, emphysema, and asthma.

Effects on the environment

The increase in UV radiation due to Stratospheric ozone depletion also has an enormous negative impact on the environment which is cited below.

• Reduced plant growth: Ozone depletion can reduce the photosynthesis rate and thus plant growth is reduced.
• Increased production of harmful compounds: In the presence of excessive levels of UV radiation, plants produce harmful volatile organic compounds, like isoprenes.
• Increased degradation of materials: Exposure to UV radiation due to Ozone depletion can increase the rate of degradation natural materials, such as wood.
• Increased disease in domestic animals: Ozone depletion can increase diseases in domestic animals such as squamous cell carcinomas in cats, cattle, sheep, and horses.
• Reduced agricultural crop yields: Ozone depletion can lead to less production of crops which may lead to reduced food supply. .
• Increased susceptibility to diseases and pests: Ozone depletion makes the plants more susceptible to diseases, pests, and other stresses such as harsh weather.

Stratosphere Ozone Layer Protection

The stratospheric ozone layer protects the living beings on the Earth from excessive ultraviolet radiation coming from the Sun. The anthropogenic emission of ozone-depleting substances (ODS) which are commonly used in refrigeration and air conditioning, foam products, aerosols, solvents, and fire extinguishers, has been continuously damaging the Stratospheric ozone layer.

• Air-conditioning and refrigeration equipment that does not use HCFCs as refrigerant should be used.
• Aerosol products that do not use HCFCs or CFCs as propellants should be bought.
• Regular inspection and maintenance of air-conditioners and refrigerators should be conducted to prevent and minimize refrigerant leakage.
• For existing HCFCs or CFCs-driven air-conditioners and refrigerators, the refrigerant should be recovered or recycled. Replacing or retrofitting such appliances with non-HCFC refrigerant should also be considered.
• When motor vehicles and air-conditioners need servicing, the refrigerants should be properly recovered and recycled instead of being vented into the atmosphere.

Stratospheric Ozone vs Tropospheric Ozone

The difference between stratospheric ozone and tropospheric ozone is given below:

Feature	Stratospheric Ozone (Good Ozone)	Tropospheric Ozone (Bad Ozone)
Location	Upper atmosphere (15-35 km)	Lower atmosphere (ground level to 10 km)
Formation	Photolysis of molecular oxygen (O2) by ultraviolet (UV) radiation	Chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs) in sunlight
Concentration	Relatively high and stable	Relatively low and variable
Effect on humans and environment	Protects from harmful UV radiation	Harmful to human health and ecosystems
Impact on climate	Absorbs UV radiation, contributing to Earth’s energy balance	Acts as a greenhouse gas, contributing to warming
Sources of concern	Depletion due to chlorofluorocarbons (CFCs) and other halogens	Increasing emissions from human activities like vehicles, power plants, and industrial processes
Origin	Naturally formed	It is a secondary pollutant

Conclusion: Stratospheric Ozone

The Stratospheric ozone layer protects all living beings on the Earth’s surface from harmful solar radiation (UV rays). But human activities have damaged this protection shield of the ozone layer which in turn causes the increase in UV radiation on Earth’s surface. This Stratospheric ozone layer depletion causes a severe impact on all living things on Earth including the environment. A few protection plans have been employed to heal the damage caused by human activities to the Stratospheric ozone layer under international agreements like the Montreal Protocol.

FAQs on Stratospheric Ozone

Why is Stratospheric Ozone a Problem?

A depleted Stratospheric ozone layer allows the harmful UV radiation to reach the Earth’s surface. This UV radiation causes several harmful effects on human health as well as other animals and plants on the Earth.

What is the Main Cause of Stratospheric Ozone Depletion?

The main cause of stratospheric ozone depletion is human-made ozone-depleting substances (ODS) like CFCs and halons, releasing chlorine and bromine atoms that catalytically destroy ozone molecules, thinning the ozone layer.

What is the Stratospheric Ozone vs Tropospheric Ozone?

Stratospheric ozone naturally occurs in the upper level (Stratosphere) of the atmosphere whereas tropospheric ozone is released by human activities into the lower level (Troposphere) of the atmosphere.

Is Stratospheric Ozone Harmful to Humans?

The stratospheric ozone layer is regarded as a ‘Good’ zone. It shields the Earth’s surface from harmful UV radiation coming from the Sun and protects all the living beings on Earth.

What Produces Stratospheric Ozone?

Stratospheric ozone is produced by the interaction of solar ultraviolet (UV) radiation with oxygen molecules (O2) in the stratosphere, where UV radiation breaks down oxygen molecules into atoms that combine with others to form ozone (O3).

What Level of Ozone is Harmful?

Ozone levels exceeding 0.070 parts per million (ppm) for an 8-hour average can be harmful to health, particularly affecting individuals with respiratory conditions and causing irritation to the eyes, throat, and nose.

How is Good (Stratospheric) Ozone Formed?

Good (stratospheric) ozone forms naturally in the Earth’s stratosphere when ultraviolet (UV) radiation from the sun interacts with oxygen molecules (O2), leading to the creation of ozone (O3) through a process called photodissociation.

How does the Sratospheric Ozone Layer Protect Us?

The stratospheric ozone layer shields us from harmful ultraviolet (UV) radiation by absorbing and filtering out a significant portion of the sun’s UV rays, thus reducing the risk of skin cancer, and other UV-related health issues.

How does the Ozone Layer Affect Climate Change?

The ozone layer indirectly affects climate change by altering atmospheric temperature and circulation patterns, leading to changes in weather systems and biological processes like photosynthesis, which can impact climate regulation.