Subject:
Topic:
Environmental Biology
OZONE DEPLETION
Submitted to: Mam Khushbu
Submitted by: AFSHEEN
Session:
BS Zoology (2018-2022)
Date:
11-04-2022
PUNJAB GROUP OF COLLEGES, SHARAQPUR SHARIF
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CONTENTS
 INTRODUCTION
 WHAT IS STRATOSPHERE OZONE?
 OZONE LAYER
 FORMATION OF OZONE LAYER
 OZONE HOLE
 OZONE DEPLETION
 PROCESS OF OZONE DEPLETION
 CAUSES OF OZONE DEPLETION
 EFFECTS OF OZONE DEPLETION
 SOLUTIONS TO THE OZONE DEPLETION PROBLEM
 CONCLUSION
 REFERENCE
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OZONE DEPLETION
INTRODUCTION:
Our environment is made up of different layers. Ozone layer is found in between the
stratosphere and troposphere. It acts as a shield or sunscreen from the harmful ultraviolet rays that
comes from the sun. Approximately 90% of the ozone is present in stratosphere at the height of 10
to 17 kilometer and remaining 10% is present in troposphere. Medium frequency UV radiations i.e.
200 nm to 315 nm are absorbed 97 to 99% by the ozone layer. Ozone (O3) is colour less like oxygen
(O2) but it has very harsh odour. It is estimated that out of 10 million air molecules about 2 millions
are of O2 and only 3 are of ozone. The process of ozone formation is called as photolysis.
When the UV radiations from sun strike the O2 molecules, it causes splitting of O2. Oxygen
molecules react with oxygen atoms in the upper atmosphere to form ozone. Stratospheric ozone is
measured from the ground in units called “Dobson Unit” (D.U). Normal ozone concentration is
between 300 - 350 D.U.
What is Stratospheric Ozone?
‘’The stratospheric ozone layer forms a thin shield in the upper atmosphere,
protecting life on Earth from the sun’s ultraviolet (UV) rays. It has been called the
Earth’s sunscreen’’.
Ozone is a naturally occurring gas that can be good or bad for your health and the environment
depending on its location in the atmosphere. In the layer near the Earth’s surface—the
troposphere— ground-level or “bad” ozone is an air pollutant that is a key ingredient of urban
smog. But higher up, in the stratosphere, “good” ozone protects life on Earth by absorbing some of
the sun’s UV rays.
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Ozone layer:
‘’Ozone layer is a protective layer of gas molecules located within the
stratosphere’’.
 Ozone layer is thin, fragile shield that contains relatively high concentrations of ozone.
 It shields the entire earth from much of the harmful UV radiation that comes from sun.
 The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri
Buisson.
Formation of ozone:
Chemically ozone forms when UV hits on stratosphere oxygen molecules dissociate into the
atomic oxygen:
O2 + sunlight → O + O
Atomic oxygen quickly combines with other oxygen molecules to form ozone:
O + O2 → O3
Ozone Hole:
Ozone hole is created in the region where ozone layer has been depleted. The term “Ozone Hole” is
applied when the depletion level is below 200 Dobson Unit (D.U). Ozone holes are first discovered
in Antarctica in 1970. Few years ago ozone holes are also discovered in Arctic region. Since 2000
rate of ozone depletion is increasing 0.5 percent per year. Due to depletion of Ozone UV rays are
penetrating in troposphere and leading to more ozone formation in troposphere which is causing
injurious effects on our health as ozone is toxic for our body.
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The Largest Ozone Hole to Date:
According to NASA scientists, from September 21 to 30, 2006, the average area of the ozone hole
was the largest ever observed, at 10.6 million square miles. The hole is a seasonal occurrence over
the South Pole that occurs because of special weather conditions in the Antarctic.
Source: National Aeronautics and Space Administration (NASA)
Ozone Depletion:
‘’Ozone layer depletion is the gradual thinning of the ozone layer present in the
upper atmosphere’’.




Ozone layer depletion, is simply the wearing out (reduction) of the amount of ozone in the
stratosphere.
Unlike pollution, which has many types and causes, ozone depletion is mainly caused by
major human activity.
It is harmful to nature and the atmosphere.
Ozone layer depletion is one of the major problems for the atmosphere and also for the
living beings including the flora and fauna of this earth.
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The Ozone Depletion Process:
The ozone depletion process are following:
 The stratospheric ozone depletion process begins with the emission of halogen source
gases by human activities and natural processes. Those emitted by human activities are also
called ozone-depleting substances (ODSs), include manufactured chemicals released
to the atmosphere in a variety of applications, such as refrigeration, air conditioning, and
foam blowing. Chlorofluorocarbons (CFCs) are an important example of chlorine-containing
gases.
 Emitted source gases accumulate in the lower atmosphere (troposphere) and are
transported to the stratosphere by natural air motions.
 The accumulation occurs because most source gases are highly unreactive and do not
dissolve readily in rain or snow in the lower atmosphere. Small amounts of these gases
dissolve in ocean waters.
 Natural air motions transport these accumulated gases to the stratosphere, where they are
converted to more reactive gases.
 Some of these gases then participate in reactions that destroy ozone.
 Finally, when air returns to the lower atmosphere, these reactive chlorine and bromine
gases are removed from Earth’s atmosphere by rain and snow and deposited on Earth’s
surface.
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Causes of Ozone Depletion:
Scientific evidence indicates that stratospheric ozone is being destroyed by a
group of manufactured chemicals, containing chlorine and/or bromine. These chemicals are called
‘’ozone-depleting substances’’. ODS are very stable, nontoxic and environmentally safe in the
lower atmosphere, which is why they became so popular in the first place. However, their very
stability allows them to float up, intact, to the stratosphere. Once there, they are broken apart by
the intense ultraviolet light, releasing chlorine and bromine. A single chlorine molecule can break
apart thousands of molecules of ozone. Ozone depletion are caused by two activities i.e.:
1. Natural causes
2. Man-made causes
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1. Natural causes of depletion of ozone layer:
It is found that the ozone layer gets affected by some natural causes that are
following:
a) Sun-spots
b) Stratospheric winds
c) Volcanic eruptions
a) Sun-spots:
Sunspots can be defined as temporary phenomena on the sun’s photosphere and as
regions of reduced surface temperature caused by magnetic field flux that inhibit
convection. Sunspots can have serious negative effects on the ozone layer since sunspots
usually come along with an increase in UV-B radiation which in turn can change the ozone
concentrations in the atmosphere.
b) Stratospheric winds:
Another natural cause for the depletion of the ozone layer is stratospheric winds.
Stratospheric winds lead to an increase of nitrogen oxides in the atmosphere, which in turn
amplifies the depletion of the ozone layer.
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c) Volcanic eruptions:
Volcanic eruptions can play an indirect role in the ozone layer destruction process.
Volcanoes emit large amounts of particles and aerosols when they erupt. These emitted particles
create a surface on which chemical reactions can take place which in turn can harm the ozone
layer.
2. Man-made causes of depletion of ozone layer:
Human activities are the main cause of the depletion of the ozone layer. It occurs due to
the excessive use of the man-made compounds such as:
a. Chlorofluorocarbons (CFCs)
b. Halons
c. Methyl chloroform
d. Carbon tetrachloride
e. Hydro-chlorofluorocarbons
f. Methyl bromide
a. Chlorofluorocarbons:
 CFCs are highly volatile and non-combustible so they are very quickly evaporated and
can easily reach in stratosphere where ozone is present here they start depleting ozone
molecules.
 The most widely used ODS, accounting for over 80% of total stratospheric ozone
depletion.
 Used as coolants in refrigerators, freezers and air conditioners in buildings and cars
manufactured before 1995.
 Found in industrial solvents, dry-cleaning agents and hospital sterilants.
 Also used in foam products — such as soft-foam padding (e.g. cushions and mattresses),
rigid foam (e.g. home insulation) and inhalers used by asthmatic patients.
 Moreover, CFCs also contribute to global warming.
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b. Halons:
 Halons contribute to the ozone layer depletion since they contain bromine which has
the potential to destroy the ozone in the stratosphere.
 Halons can be ten times more harmful to the ozone layer than CFCs. Halons are primarily
used in fire extinguishers.
c. Methyl Chloroform:
 Methyl chloroform is used for a variety of industrial processes for example, vapour
degreasing, some aerosols, cold cleaning, adhesive and chemical processing.
 It is mainly used for solvents to clean electronic and metal parts.
 Ultraviolet radiation breaks up the substance into chlorine, which in turn can harm the
ozone layer.
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d. Carbon tetrachloride:
 Carbon tetrachloride also contributes to the ozone layer depletion since it contains
chlorines which can harm the ozone layer.
 Carbon tetrachloride is used in refrigerators as well as for solvents, soaps and
insecticides.
 However, its use declined over the last decades after scientists discovered the negative
effects regarding the ozone layer depletion.
e. Hydro-chlorofluorocarbons:
 HCFCs (hydro-chlorofluorocarbons) are another source of the ozone layer depletion
problem.
 Although they have only a weak impact on the depletion of the ozone layer, HCFCs are
still quite harmful to the environmental system since they are strong greenhouse gases.
 HCFCs are currently replaced by HFCs since they do not contain chlorine and are
therefore considered less damaging to the environmental system.
f. Methyl Bromide:
 Methyl bromide is usually used as a fumigant in order to control pests in shipping and
agriculture.
 Methyl bromide is a serious ozone-depleting substance that is classified as Class I ozonedepleting substance.
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Effects of Ozone Depletion:
With the depletion of the ozone layer, huge amounts of UV rays can reach the Earth’s
surface. This has severe consequences that are following:
1) Increased level of UV radiation:

One of the main effects of the depletion of the ozone layer is an increased level of UV
radiation which has many severe effects on humans as well as on other life forms.

Since the ozone layer usually blocks the radiation, a depletion of the ozone layer
increases the level of ultraviolet radiation.

Excessive exposure to radiation can cause severe health issues for humans and could
also affect animals and plants in an adverse way.
2) Carcinoma:

One big health issue is carcinoma caused by excessive exposure to radiation caused by
ozone layer depletion.

This is especially true for squamous and basal cell carcinomas, which scientists link to
exposure to UVB radiation.

The absorption of UVB radiation causes changes in the DNA structure which in turn
result in transcription errors when the DNA parts replicate.

Thus, ozone layer depletion contributes to an increased probability of carcinoma.
3) Melanoma:

Another form of skin cancer is malignant melanoma, which can also be caused by
radiation due to ozone layer depletion.

It is quite harmful with a lethal rate between 15 and 20 percent of all diagnosed cases.

Scientists believe that the exposure to UVA as well as the exposure to UVB radiation can
cause Melanoma.
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
Since ozone layer depletion leads to an increase in UVB exposure, it can be seen as a
cause for Melanoma.
4) Effects on human health:

Apart from serious health conditions like cancer, the ozone layer depletion can also have
additional adverse effects on human health.

For example, it can lead to sunburns, eye cataracts(clouding of the eye’s lens which
reduces vision and if left untreated, may cause blindness), aging or also to a weak
immune system which in turn can lead to additional diseases.
5) Increased tropospheric ozone:

The depletion of the ozone layer also leads to an increase in tropospheric ozone which in
turn can lead to health issues.

These health issues can be especially severe for elderly persons, children, or all persons
who have respiratory difficulties.
6) Increased vitamin D production:

Ozone layer depletion can also lead to an increase in vitamin D production since vitamin
D is produced by ultraviolet light in the skin.

An increase in vitamin D in moderate amounts is rather uncritical or may even be
beneficial to human health.

However, if the increase is too big, it can cause severe health conditions and can also
increase the probability of mortality.
7) Change in biogeochemical cycles:

Since the depletion of the ozone layer contributes to an increase in UVB radiation, this
increase can lead to a change in biogeochemical cycles.

This change in biogeochemical cycles can alter sources and sinks of greenhouse gases
and thus can indirectly contribute to the global warming issue.
8) Effects on marine life:

Ozone layer depletion can also harm marine life in a severe way.

An increase in UVB radiation due to the depletion of the ozone layer can harm the
growth of plankton.

Since plankton is consumed by many sea animals, a decrease in plankton may harm
many other sea animals as well.
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
A decrease in plankton will therefore lead to a disruption of the whole marine food
chain.
9) Effects on animals:

The depletion of the ozone layer not only has adverse effects on marine life, but also on
many other animals.

Similar to humans, animals can also suffer from skin cancer and additional diseases
caused by UVB radiation.

The increase in UVB radiation is even more harmful to animals since they are not able to
protect against it, in contrast to humans who can use sun protection measures.
10)
Effects on Plants:

Ozone layer depletion may also have an adverse effect on the growth of plants.

Many plants are used to certain environmental conditions since they have developed
their characteristics over many million years.

Thus, they may react quite sensitive to changes in their natural environmental
conditions like an increase in UVB radiation due to ozone layer depletion.
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Effects on crops:

The depletion of the ozone layer may also affect crop yields.

UVB radiation is known to be able to change parts of the plant’s DNA. This may lead to
reduced crop yields or other issues related to it.
12)
Environmental impact:

As we have already seen, there are several adverse effects of ozone layer depletion on
our environment.

However, it is hard to estimate how severe the overall effect on the environment would
be if the ozone layer continued to be depleted since there are many chain reactions that
have to be taken into account.

However, it is estimated that without our ozone layer, the whole food chain would
collapse within a few days or weeks.

Thus, we should make sure to take measures in order to preserve the ozone layer.
13)
Economic impact:

Since an increase in UVB radiation is likely to lead to lower crop yields and other
harmful effects, the depletion of the ozone layer is likely to imply serious
financial downsides on a global scale.
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Solutions to the Ozone Depletion Problem:
There are different ways to solve the ozone depletion problem which are
following:
1) Limit transportation networks:
 One measure against ozone layer depletion would be the reduction of private car use.
 Since cars emit greenhouse gases which also turn into smog, cars vastly contributes to
the ozone layer depletion issue since smog acts as a kind of catalyst in the ozone
depletion process.
 Moreover, the use of many vehicle fluids like refrigerants or anti-freeze fluid also
contribute ozone depletion since they contain chemicals like chlorines or bromines
which hurt the ozone layer.
 Thus, switching from private car use to public transport can be quite beneficial for our
environment and also for our ozone layer.
2) Renewable energies:
 The use and extension of renewable energies is a crucial step in order to meet the ozone
depletion issue.
 Apart from nuclear energy, fossil resources like coal are an important source for
electricity generation.
 However, the combustion of coal leads to the emission of CFCs, which in turn leads to a
depletion of the ozone layer.
 Therefore, a switch from fossil to renewable energies would mitigate the ozone
depletion problem since we could avoid the emission of CFCs and thus protect the ozone
layer.
3) Stop Deforestation:
 Stopping deforestation could indirectly help to mitigate the problem of ozone depletion.
 Since deforestation contributes to global warming, it also indirectly affects the ozone
layer.
 Global warming increases water vapor, which in turn blocks ozone production.
 Moreover, through the burning of would, substances harmful to the ozone layer may be
produced.
 Thus, avoiding deforestation could also contribute to a reduction in ozone layer
depletion.
4) Recycle and reuse:
 We should also reuse our products as much as possible.
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 If we do not use them anymore, we should make sure that they can be recycled properly.
In this way, we can decrease the demand for natural resources.
 Therefore, we can also avoid the adverse effect of the extraction process of resources on
the environment.
 Through the reduction in energy demand, we can decrease the emission of harmful gases
and thus lower the adverse effect on the ozone layer.
5) Avoid the excessive use of fertilizers:
 Since many fertilizers contain nitrogen and other harmful substances, excessive use of
these fertilizers can harm the ozone layer.
 Thus, we have to make sure that fertilizers are used in a responsible way.
 This could be done through government regulations and also through education of
farmers on the adverse effects of the use of nitrogen-based fertilizers on the ozone
layer.
6) Avoid the use of pesticides:
 In some countries, methyl bromide is still used in pesticides.
 However, methyl bromide is a serious contributor to the ozone layer depletion issue.
 Thus, banning this substance would mitigate the ozone depletion problem.
7) Reduce CFCs:
 As we have seen in our previous analysis, CFCs are a major factor for ozone depletion.
 CFCs are used in many industries and for the production of a huge variety of products.
 This includes refrigerators, air conditioning and aerosol sprays.
 Thus, if we are able to replace the CFCs through other substances, we would be able to
greatly reduce CFC emission and therefore to protect the ozone layer.
8) Reduce nitrous oxides:
 Similar to CFCs, nitrous oxides are also produced in many industrial processes and in the
manufacturing processes of several products.
 Since nitrous oxides are known to affect the ozone layer in an adverse way, reducing the
amount of nitrous oxides and replacing them with other substances would also mitigate
the issue of ozone depletion.
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9) Government Regulations:
 Governments and other institutions have the responsibility to take measures against
ozone layer depletion.
 It is in our collective interest that we sustain the ozone layer.Otherwise, we would suffer
from dramatic health consequences.
 Therefore, governments should ban substances like CFCs or nitrous oxides wherever
they can be replaced by other substances that do not harm the ozone layer.
 Moreover, it would make sense to increase tax rates for substances that are harmful to
the ozone layer.
 Through the increase in taxes, industries would have a financial incentive to substitute
harmful substances like CFCs through other harmless substances which would in turn
mitigate the ozone depletion issue.
10)
Education:
 Education is another measure to fight ozone depletion.
 This is either true on an individual level as well as for industrial purposes.
 We should educate children from a young age about the serious adverse problems that
come with ozone depletion.
 Therefore, when children grow up, they may carry their knowledge into adulthood and
take measures against ozone layer depletion in their daily lives.
 This could mean that they are more likely to use public transport instead of cars.
 Moreover, we also have to convince industries that they have a social responsibility.
 Instead of just looking at profits and shareholder value, industries should also focus on
reducing harmful substances and therefore saving the ozone layer. Profit maximization
and environmental goals seem to contradict on the first glance.
 However, industries could increase their brand value by saving the environment since
they could communicate their measures against ozone depletion to customers.
Customers may in turn be more willing to buy environmentally friendly products.
 Thus, in this way, industries may be able to increase profits but also contribute to saving
our environment.
11)
Convince others:
 We can all make our contribution to a reduction of ozone depletion on a daily basis.
 This may include small measures like the substitution of cars through public transport or
other measures of transport.
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 It may also include buying local food instead of products that have been produced in
foreign countries in order to avoid the adverse consequences of long transportation
distances.
 However, our contribution is not enough! We should also convince others. This may
include convincing your family and friends to change their daily life behavior.
 By doing so, you can convince many people who in turn may further convince other
people. Thus, you can make a big impact in order to save the ozone layer.
Conclusion:

Ozone layer depletion is a deep crisis which leads to increased UV-B radiation reaching the
surface of the Earth affecting humans and all the living organisms.

Anthropogenic activities this have been the main cause for ozone layer depletion leading to
global climatic changes in this century.

This leads to a number of health problems like heat-related issues, skin cancer, and various
other ecological disturbances that affect biotic life.

Hence every individual should be well aware of the harmful effects of all the causing agents
of ozone layer depletion like CFC, plastics, fossil fuel etc. and should reduce and avoid using
them.

We all should pledge to preserve nature and make this world sustainable for everyone to
live.
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Reference
 www.epa.gov/ozone/strathome.html
 www.researchgate.net
 www.topper.com
 Csl.noaa.gov
 https://environmental-conscience.com
 https://brainly.in
 www.google.com/images
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