OZONE LAYER DEPLETION: CAUSES AND EFFECTS
BY
UDOH, A.O.
DEPARTMENT OF PHYSICS
NWAFOR ORIZU COLLEGE OF EDUCATION, NSUGBE
Abstract
Ozone layer is part of the stratosphere which absorbs the harmful UV rays of the
sun and prevents it from reaching the earth surface. Some human activities (such
as industrial by-product) release chemicals into the air that remove ozone, thus
known as ozone, thus known as ozone layer depletion. The main cause of ozone
layer depletion is chlorine released from man-made substance such as
chlorofluorocarbons (CFCs). Other ozone depleting substances (ODS) include
bromine, halons, carbontetrachloride, methylbromide, etc. Once the depletion
occurs, the result is that the earth would be in direct contact with the sun’s heat
and its damaging ultraviolet rays. When stratospheric ozone depletion is so severe
in particular regions, such depletion is termed ‘ozone hole’. The main effect of
ozone layer depletion is increase in ultraviolet radiation reaching the earth. Other
effects include genetic changes, reduced plant growth, damage to possessions, etc.
Growing concern for ozone for ozone depletion has led to the adoption of the
Montreal Protocol in September 1987 by 24 countries including the European
Economic Community in order to reduce and control industrial emission of
chlorofluorocarbons (CFCs). The Protocol called for the parties to phase down
the use of CFCs, halons and other man-made ozone depleting chemicals (ODCs).
You can also help to reduce the amount of CFCs entering the atmosphere by
replacing your age-old refrigerators and air conditioners that are not energy
efficient, disposing your old refrigerator properly to make sure CFCs aren’t
released into the air, etc. It is very important to reduce our exposure to UV
radiation by avoiding the sun between 11.00 a.m. to 4.00 p.m. particularly during
season, using wrap-around sunglasses to protect our eyes, etc. If the causes of
ozone layer depletion are not addressed, the end result would be global warming.
Hence, government should try and implement certain rules to guide/monitor the
release of ozone-depleting substances into the atmosphere.
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INTRODUCTION
The ozone layer is a special shield of gas in the horizontal that captures the
heat of the sun on the earth (Azubuike et al, 2012). It is part of the stratosphere
and is composed of the ozone (O3) molecules. These molecules absorb the
harmful UV rays of the sun and prevent it from reaching the earth surface.
Approximately 90% of all ozone is produced naturally in the stratosphere. While
ozone can be found through the entire atmosphere, the greatest concentration
occurs at an altitude of about 25km. This band of ozone-rich air is known as the
„‟ozone layer‟‟ (Environment Canada, 2010). In recent years the thickness of this
layer has been decreasing, leading in extreme cases, to holes in the layer. Some
human activities release chemicals into the air that remove ozone. The main cause
of ozone layer depletion is the increased stratospheric concentration of chlorine
from industrially produced chlorofluorocarbons (CFCs), halons and selected
solvents. Once in the stratosphere, every chlorine atom can destroy up to 100,000
ozone molecules. Less ozone in the atmosphere increases the amount of ultraviolet (particularly UV-β) rays that reach the earth.
OZONE
Ozone is created in the second region of stratosphere when UV radiation from
the sun strikes molecules of oxygen (O2) and causes the two oxygen atoms to split
apart. If a freed atom bumps into another O2, it joins up, forming ozone (O3). This
process is known as photolysis (Sivasakthivel and SivakumarReddy, 2011).
Hence, it is a tri-atomic form of oxygen (O3). Most ozone occurs in the second
region of atmosphere called stratosphere. Stratospheric ozone filters out most of
the sun‟s potentially harmful shortwave ultraviolet (UV) radiation. It is colourless
and has a very harsh odour. It can also occur in very small amount in the lowest
part of the atmosphere known as the troposphere through a reaction between
sunlight and volatile organic compound (VOCs) and nitrogen oxides (NOx).
Some of these are produced by human activities such as smoke from exhaust
pipes of cars and these constitute urban smog which can be harmful to human
health.
OZONE LAYER DEPLETION
Ozone layer depletion is the term commonly used to describe the thinning of
ozone layer in the stratosphere. Damage to the stratospheric ozone was first
identified in 1974 (Verisae, 2009). Ozone depletion occurs when the natural
balance between the production and destruction of ozone in the stratosphere is
tipped in favour of destruction. The result is that the earth would be in direct
contact with the sun‟s heat and its damaging ultraviolet rays.
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Although natural phenomena can cause temporary ozone loss, chlorine and
bromine released from man-made compounds such as CFCs are now accepted as
the main cause of this depletion (Angell and Korshover, 2005). Ozone depleting
substances (ODS) generally contain chlorine, fluorine, bromine, carbon, and
hydrogen in varying properties and are often described by the general term
„halocarbons‟. ODS have a long lifetime in our atmosphere, up to several
centuries. This means that most of the ODS we‟ve released over the last 80years
are still making their ways to the stratosphere, where they will add to the ozone
destruction. Hence, once they have been released into the atmosphere, they remain
there for as long as 20years.
Apart from chlorofluorocarbons (CFCs), other ozone depleting substances or
chemicals include carbon tetrachloride, methyl bromide, methyl chloroform,
halons, hydrobromo fluorocarbons and hydro fluorocarbons. These chemicals
have a range of uses. For instance, CFC is an organic compound, and is primarily
used as a coolant in refrigerators, freezers and air conditioners in buildings and
cars. It is also used in firefighting equipment , aerosols, the production of
installed-foam (for home insulation) and soft foam padding (for cushions and
mattresses), production of industrial solvents, dry cleaning agents and hospital
sterilants. The CFC emission reaches the stratosphere and destroys the ozone
molecules there.
Years of research have determined that chlorofluorocarbons top the list of
ozone layer depletion because they are not destroyed by rain or broken down in
the lower atmosphere. Once they reach the stratosphere, the sun‟s ultraviolet rays
break down the compound, thus releasing chlorine. The resulting chlorine is
what damages the ozone in a repetitive process. In fact, one chlorine atom will
continue to destroy the ozone for as long as two years (Verisae, 2009).
Methyl bromide is used for soil sterilization in strawberry production. Methyl
chloroform is used mainly in industry –for vapour degreasing, some aerosols, cold
cleaning, adhesive and chemical processing. Halons and carbon tetrachloride are
used in some fire extinguishers. Exhaust gases from jet aircrafts and artificial
satellites discharge nitric oxide (NO), nitrogen dioxide (NO2), etc which
immediately react with ozone.
O3 +
NO
(ozone) (nitric oxide)
O3
(ozone)
+
NO2
(nitrogen dioxide)
O2 + NO2
(oxygen) (nitrogen dioxide)
O2 + NO3
(oxygen) (nitrogen trioxide)
(Anil and Arnab, 2005)
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Thus, when these chemicals are injected in the stratosphere, they consume ozone
and reduce its concentration.
OZONE HOLE
There is a common misconception that the “ozone hole” is really a hole in the
ozone layer or that the ozone hole should be above the source of CFCs. However,
CFCs are well mixed globally, in the troposphere and the stratosphere. When the
“ozone hole” occurs, the ozone in the lower stratosphere is destroyed. The upper
stratosphere is destroyed. The upper stratosphere is less affected, so that the
amount of ozone over the continent decreases by 50 percent or even more. The
ozone does not disappear through the layer but rather there is a depression.
Technically, the term „ozone hole‟ implies regions of the ozone layer where
stratospheric ozone depletion is so severe. In 1979, ozone hole was observed in
the sky over Antarctica- here ozone layer thickness was reduced by 30 percent
(Anil and Arnab, 2005). The reason for the occurrence of the ozone hole above
Antarctica is not because there are more CFCs concentrated but because the low
temperatures help form polar stratospheric clouds. In fact, there are findings of
significant and localized „ozone holes‟ above other parts of the earth.
EFFECTS OF REDUCED OZONE
The main potential consequence of ozone depletion is increase in UV-B
radiation at ground level. A one percent loss of ozone leads to a two percent
increase in UV radiation. Increased penetration of solar UV-B radiation is likely
to have profound impact on human health with potential risks of eye diseases, skin
cancer and infectious diseases (Morrisette, 1995).UV radiation can damage the
lens and cornea of the eye (resulting to corneal cataracts which can lead to
blindness). It can adversely affect the immune system causing a number of
infectious diseases and is likely to develop non-melanoma skin cancers in light
skinned human beings. Ozone chemicals can cause difficulty in breathing, chest
pain, throat irritation and hamper lung functioning.
Other effects of reduced ozone include:
 Reduced plant growth: increased UV radiation can reduce plant
photosynthesis and growth; alter the time of flowering, as well as the
number of flowers.
 Genetic changes: increased chance of mutation can result in small
organisms.
 Damage to possessions: materials that are sensitive to ultra-violet
radiation may wear out or age quicker.
Effects on marine ecosystems: ultraviolet rays can influence the survival rates of
marine microscopic organisms like plankton (which plays important role in
converting atmospheric carbon dioxide into
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
oxygen) by affecting their orientation and mobility. This eventually
disturbs and affects the entire ecosystem.
Decrease in the ozone in the stratosphere can also result to an increase in the
ozone present in the lower atmosphere. Ozone present in the lower atmosphere is
mainly regarded as a pollutant and a greenhouse gas that can contribute to global
warming and climate change. At the same time, increase in the level of ozone in
the lower atmosphere can enhance the ability of sunlight to synthesize vitamin D,
which can be regarded as an important beneficial effect of ozone layer depletion.
PROTECTING THE OZONE LAYER
Growing concern for ozone depletion led to the adoption of the Montreal
Protocol in 1987, in order to reduce and control industrial emission of
chlorofluorocarbons (CFCs) (Buzzle, 2012). The Montreal Protocol on
„Substances that Deplete the Ozone Layer‟ was negotiated and signed by 24
countries and by the European Economic Community in September 1987. The
Protocol called for the parties to phase down the use of CFCs, halons and other
manmade Ozone Depleting Chemicals (ODCs). In 1990 and 1992, the Protocol
was supplemented by agreements made in London and Copenhagen respectively,
where the same countries promised to stop using CFCs and most of the other
chemical compounds destructive to ozone by the end of 1995. The key
agreements of the Protocol are: banning the release of the ODS during refrigerator
use, maintenance and disposal. It also made it mandatory for the manufacturers to
label the substances that contain the harmful ODS. In 1994, the United National
General Assembly voted to designate September 16 as „World Ozone Day‟, to
commemorate the signing of the Montreal Protocol on that date in 1987
(Wikipedia, 2012).
Powerful countries like USA, and some other European countries have agreed
to ban the total production of the CFCs. This is one of the best step forward since
these countries produce more than quarters of CFCs in the world. However, there
is challenging issue on whether other countries should also be encouraged to
totally ban the CFC production rather than limiting or phasing it out. This is
because CFC sources are very widespread. For instance, some industrial avenues
like printing, dry cleaning, baking, etc use CFCs to some extent. Hence, a total
ban on the CFC usage will break these industries and lots of products would be
lost. Also, there would be mass loss of employment. Thus, gradual phase out of
the CFCs or finding safer alternatives for CFC is the only solution that remains.
HOW YOU CAN HELP TO PREVENT OZONE DEPLETION
The world today faces a serious catastrophic problem in the form of rapid
ozone depletion. Much damage has already been done – there is huge amount of
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CFC gas floating in the stratosphere, destroying ozone. You can help to reduce the
amount of CFCs entering the atmosphere by:
 Replacing your age-old refrigerators and air conditioners that are not
energy efficient.
 Disposing your old refrigerators properly to make sure CFCs aren‟t
released into the air.
 Checking your vehicle air conditioning unit to ensure that there is no
leaks.
 Unplugging the electronic instruments when they are not in use.
These instruments emit CFCs in air when they are not in use and are
just plugged in.
 Prefer buying energy efficient appliances like the fluorescent bulbs.
In fact, try to use products which are labeled „ozone-friendly‟.
 Using public transportation most often instead of your own private
vehicle. This will help a big deal in order to reduce the quantity of
exhaust gases injected into the atmosphere.
 Encouraging growth of plants that produce oxygen and discouraging
deforestation.
 Decreasing/controlling the release of high temperature
steam/moisture to the atmosphere.
 Replacing halon fire extinguishers with alternatives (e.g. carbon
dioxide or foam)
 Suggesting school activities to increase awareness of the problem and
initiating local action.
Thus, our individual efforts can go a long way in saving the Earth‟s blanket.
Truly, your role might be small but if all human work together, the results would
be remarkable.
WAYS TO PROTECT OURSELVES AGAINST UV RADIATIONS
It is very important to reduce our exposure to UV radiation. This can be
achieved through the following ways:
 Avoiding the sun between 11.00 a.m. to 4.00 p.m. particularly during dry
season.
 Using sunscreen sun protection factor (SPF) 15 to 30+.
 Using wrap-around sunglasses to protect your eyes.
 Staying in the shade when outside.
 Wearing sun-protective clothing, such as hats and long sleeved shirts.
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CONCLUSION
The ozone layer acts as a natural filter, absorbing most of the sun‟s burning
ultra-violet (UV) rays. Ozone is now being destroyed much faster than it is being
created. Stratospheric ozone depletion leads to an increase in UV that reach the
earth‟s surface, where it can disrupt biological processes and damage a number of
materials. If the causes of ozone layer depletion are not addressed, the end result
would be global warming.
Increased concern over the ozone layer has led several countries to regulate the
production or uses made of CFCs. For instance, the United States banned the use
made of CFCs as aerosol propellants in 1978. Other countries like Belgium and
Portugal have also banned the production of CFCs altogether. Thus, in order to
reduce further depletion of the ozone layer, government should try and implement
certain rules to guide/monitor the release of ozone-depleting substances into the
atmosphere.
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Quassi-biennial and Long-term
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Azubuike, K.A. et al (2012)
Professional Competency Needs of Science
Teachers for Effective Classroom Management in Climate Change
Literacy and Environmental Education: A Case Study of Biology
Teachers. Journal of Research in Education. 1(1) P.118
Buzzle (2012) Ozone Layer Depletion: Effects and Causes of Ozone Depletion.
http://www.buzzle.com/articles/ozone-layer-depletion_effects-and
Environment Canada (2010)
Depletion of the Ozone Layer and Its
Impacts. http: //www.ec.gc.ca/ozone/default.asp?lang=En&n=6798FAB 0-1
Morrisette, P.M. (1995) The Evolution of Policy Responses to Stratospheric
Ozone Depletion. Natural Resources Journal 29.
Sivasakthivel, T. and Siva Kumar Reddy, K.K. (2011) Ozone Layer Depletion
and Its Effects: A Review . International Journal of Environmental
Science and Development. 2(1) February.
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http: //www.verisae.com/blog/bid/183346/causes-of-ozone_layer.
Wikipedia (2012) Ozone Depletion. Wikipedia, the Free Encyclopedia.
http://en.wikipedia.org/wiki/ozone depletion.
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