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Chlorofluorocarbons (CFCs) and their effect on the atmosphere
Abdullah Al Ashraf; Nasr Bensalah; Khan Mohammed Mosiur Rahman
Qatar University; Department of Chemistry and Earth Sciences, College of Arts and Sciences
Introduction
What has been done to limit CFCs
References
Conclusion
CFCs Effect on the Ozone Layer
(Chemistry of Ozone Depletion by CFCs)
Chlorofluorocarbons or CFCs (also well-known as Freon) are non-toxic, non-
flammable and non-carcinogenic. They mainly contains fluorine atoms, carbon
atoms and chlorine atoms. The 5 main CFCs include:
• CFC-11 (trichlorofluoromethane - CFCl3),
• CFC-12 (dichloro-difluoromethane - CF2Cl2),
• CFC-113 (trichloro-trifluoroethane - C2F3Cl3),
• CFC-114 (dichloro-tetrfluoroethane - C2F4Cl2), and
• CFC-115 (chloropentafluoroethane - C2F5Cl). [1]
The lifetime of CFCs in the atmosphere is about 20 to 100 years, and one
chlorine atom may destroy more than 100,000 ozone molecules before it is
transformed into a non-reactive species.[2] Although the emissions of CFCs
around the developed world have largely controlled due to international
conformity, the damage to the stratospheric ozone layers are still not stopped.
CFCs are released from refrigeration, propellant and cleaning devices and
processes. Once they are in the Earth's lower atmosphere, they tend to persist for
years due to their stable chemical makeup. Their lengthy lifespan allows some
CFCs to ultimately reach the upper stratosphere. Once in the stratosphere,
ultraviolet light from the sun breaks CFC molecular bonds, releasing chlorine
atoms. Free chlorine atoms then undergo a series of chemical reactions that
destroy the ozone layer by thinning its concentration. The destruction of ozone
requires atomic chlorine produced by sunlight:
Sunlight also drives the following reactions [5] :
Finally, a reduced ozone layer allows stronger and more harmful wavelengths of
light to enter the Earth's atmosphere.
When the depletion of ozone layer becomes a phenomenon for our survival on this
earth, scientists and people from different countries come forward to stop this
depletion by taking necessary steps. Sweden is the first country which banned
CFC- containing aerosol sprays on January 23, 1978. After that some other
countries including Canada, USA and Norway also followed the same. But the
most significant agreement that has been taken internationally is called “Montreal
Protocol’’ on substances that deplete the ozone layer”. This agreement began in
1987 and phased out completely by 1996 where, 93 nations agreed to phase-out
process to stop production and use of ozone-destroying substances. In 1990, the
international community set a unified objective of reducing CFCs by at least 50%
by the year 1999. Additional CFCs uses, such as in solvents, foaming agents in
plastics, and any remaining aerosol sprays, were given a production end date of
1996. The largest source of ozone-depleting chemicals goes to CFC from air
conditioners in cars. Special equipment has been intended for auto service shops to
recycle the CFCs and prevent them from being released in the air. This service has
been regulated since the end of 1993. Refrigerator servicing and disposal also
followed similar guidelines regarding the CFCs used in refrigerants. The EPA also
established a CFC certification program to test the refrigerant recovery and
recycling equipment used by manufacturers and importers. Nowadays most of the
country in the world is very concern about the using of CFC- Containing items. [7]
Finally, we can say that today’s world is more serious about the ozone depletion
because if the ozone layer deplete quickly than we will left nothing for our
future generation. Hence, to control the depletion of ozone layer we have to stop
the use of CFCs. Scientists are doing their best to save the ozone layer by
recommending the use of substitutes of CFCs which doesn’t harmful for ozone.
As a result, we can see positive result over this phenomenon. Scientists showed
that, because of banned the using of CFCs which are the main cause of ozone
depletion- the ozone depletion process has been decreasing from few years.
Although the necessity of CFCs are supplementary, but it is our duty to save our
planet by stop uses of CFCs or using non-harmful substitutes and to protect the
ozone layer.
[1] Enviropedia (Last updated, 20012) Types of CFCs.Retrieved-April,8,2013,from
http://www.enviropedia.org.uk/Ozone_Depletion/CFCs.php
[2] Ibanez J.G. (Published: 2007), Environmental Chemistry: Fundamentals (The chemistry of
processes in atmosphere). Life time of CFCs, Page Number: 82
[3] Busman J.S. & Belen C. (Last Updated 26, October, 2008) Important Components of Ozone.
Retrieved November, 20, 2008 from http://www.umich.edu/~gs265/society/ozone.htm
[4][6]History of CFCs(Last updated 16, Nov., 2011) Figure:1, 2. Retrieved- April, 5, 2013, from
http://www.meti.go.jp/policy/chemical_management/ozone/files/pamplet/panel/08e_basic.pdf
[5] Ibanez J.G. (Published: 2007), Environmental Chemistry: Fundamentals (The chemistry of
processes in atmosphere). Chemical reactions of CFCs, Page Number: 114
[7] Eggerman S. (Last Updated-19, November, 2000) Prevention of Ozone Depletion Retrieved
November 17, 2008 from http://cesium.cs.jmu.edu/richarja/cs348/prevention.html
Fig 2: Chlorofluorocarbons: Silent Destroyers of the Ozone Layer [6]
Because of the special characteristics such as inflammability and non-toxicity
of CFCs encouraged its production and consumption particularly in developed
countries, after the 1960's. The modern lifestyle of the second half of the 20th
century had been made possible by the use of CFCs. Man-made CFCs
however, are the main cause of stratospheric ozone depletion. The most
common uses of CFCs are: [3]
• Refrigerants for refrigerators, automobiles and air-conditioners
• Cleaning agents for semi-conductors and precision parts
• Foaming agents for insulating materials and packing cushions
• Propellants for aerosol sprays
Uses of CFCs
Fig 1: The Mechanism of the Ozone Layer Depleted by Ozone
Depleting Substances [4]
Cl