CFCs Chlorofluorocarbon (CFC) is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. A common subclass is the hydrochlorofluorocarbons (HCFCs), which contain hydrogen, as well. Freon is DuPont's brand name for CFCs, HCFCs and related compounds. Other commercial names from around the world are Algofrene, Arcton, Asahiflon, Daiflon, Eskimo, FCC, Flon, Flugene, Forane, Fridohna, Frigen, Frigedohn, Genetron, Isceon, Isotron, Kaiser, Kaltron, Khladon, Ledon, Racon, and Ucon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Chlorofluorocarbons (CFCs) are a family of chemical compounds developed back in the 1930's as safe, non-toxic, non-flammable alternative to dangerous substances like ammonia for purposes of refrigeration and spray can propellants.

Their usage grew enormously over the years. One of the elements that make up CFCs is chlorine. Very little chlorine exists naturally in the atmosphere. But it turns out that CFCs are an excellent way of introducing chlorine into the ozone layer. The ultraviolet radiation at this altitude breaks down CFCs, freeing the chlorine. Under the proper conditions, this chlorine has the potential to destroy large amounts of ozone. This has indeed been observed, especially over Antarctica. As a consequence, levels of genetically harmful ultraviolet radiation have increased. Production of new stocks ceased in most countries as of 1994 However many countries still require aircraft to be fitted with halon fire suppression systems because no safe and completely satisfactory alternative has been discovered for this application. There are also a few other, highly specialized uses. These programs recycle halon through "halon banks" coordinated by the Halon Recycling Corporation to ensure that discharge to the atmosphere occurs only in a genuine emergency and to conserve remaining stocks. Development of alternatives for CFCs Work on alternatives for chlorofluorocarbons in refrigerants began in the late 1970s after the first warnings of damage to stratospheric ozone were published.

The hydrochlorofluorocarbons (HCFCs) are less stable in the lower atmosphere, enabling them to break down before reaching the ozone layer. Nevertheless, a significant fraction of the HCFCs do break down in the stratosphere and they have contributed to more chlorine buildup there than originally predicted. Later alternatives lacking the chlorine, the hydrofluorocarbons (HFCs) have an even shorter lifetimes in the lower atmosphere. One of these compounds, HFC-134a, is now used in place of CFC-12 in automobile air conditioners. Hydrocarbon refrigerants (a propane/isobutane blend) are also used extensively in mobile air conditioning systems in Australia, the USA and many other countries, as they have excellent thermodynamic properties and perform particularly well in high ambient temperatures.

One of the natural refrigerants (along with Ammonia and Carbon Dioxide), hydrocarbons have negligible environmental impacts and are also used worldwide in domestic and commercial refrigeration applications, and are becoming available in new split system air conditioners Applications and replacements for CFCs Application CFC History Refrigerators from the late 1800s until 1929 used the toxic gases, ammonia (NH3), methyl chloride (CH3Cl), and sulfur dioxide (SO2), as refrigerants. Several fatal accidents occurred in the 1920s because of methyl chloride leakage from refrigerators. People started leaving their refrigerators in their backyards. A collaborative effort began between three American corporations, Frigidaire, General Motors and DuPont to search for a less dangerous method of refrigeration. In 1928, Thomas Midgley, Jr. aided by Charles Franklin Kettering invented a "miracle compound" called Freon. Freon represents several different chlorofluorocarbons, or CFCs, which are used in commerce and industry.

The CFCs are a group of aliphatic organic compounds containing the elements carbon and fluorine, and, in many cases, other halogens (especially chlorine) and hydrogen. Freons are colorless, odorless, nonflammable, noncorrosive gases or liquids. Chlorofluorocarbons (CFCs) are highly stable compounds that were used as propellents in spray cans and in refrigeration units. They are several organic compounds composed of carbon, fluorine, chlorine, and hydrogen. CFCs are manufactured under the trade name Freon . The invention of chlorofluorocarbons (CFCs) in the late 1920s and early 1930s stemmed from the call for safer alternatives to the sulfur dioxide and ammonia refrigerants used at the time, CFCs found wide application after World War II. Chloroflourocarbons were first created in 1928 as non-toxic, non-flamable refrigerants, and were first produced commercially in the 1930's by DuPont.

The first Chlorofluorocarbon was CFC-12, a single carbon with two chlorines and two Fluorines attached to it. These halogenated hydrocarbons, notably trichlorofluoromethane (CFC-11, or F-11) and dichlorodifluoromethane (CFC-12, or F-12), have been used extensively as aerosol-spray propellants, refrigerants, solvents, and foam-blowing agents. They are well-suited for these and other applications because they are nontoxic and nonflammable and can be readily converted from a liquid to a gas and vice versa. Chlorofluorocarbons or CFCs (also known as Freon) are non-toxic, non-flammable and non-carcinogenic. They contain 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). CFCs have been found to pose a serious environmental threat. Studies undertaken by various scientists during the 1970s revealed that CFCs released into the atmosphere accumulate in the stratosphere, where they had a deleterious effect on the ozone layer. Stratospheric ozone shields living organisms on Earth from the harmful effects of the Sun's ultraviolet radiation; even a relatively small decrease in the stratospheric ozone concentration can result in an increased incidence of skin cancer in humans and in genetic damage in many organisms. In the stratosphere the CFC molecules break down by the action of solar ultraviolet radiation and release their constituent chlorine atoms.

These then react with the ozone molecules, resulting in their removal. CFCs have a lifetime in the atmosphere of about 20 to 100 years, and consequently one free chlorine atom from a CFC molecule can do a lot of damage, destroying ozone molecules for a long time. Although emissions of CFCs around the developed world have largely ceased due to international control agreements, the damage to the stratospheric ozone layer will continue well into the 21st century. In 1978 The Montreal Protocol was adopted as a framework for international cooperation regarding CFC control on the basis of the Vienna Convention for the Protection of the Ozone Layer. Data compiled from The British Antarctic Study, NASA, NASA Ozone Watch, Environment Canada, UNEP, EPA and other sources as stated and credited Updated Daily-Researched By Charles Welch- This Website is a project of the The Ozone Hole Inc. Visit our other website Copyright Charles Welch The Ozone Hole Environment for Kids: Ozone Layer Depletion Ozone Layer Depletion What is ozone? Ozone is a gas made up of molecules that are formed by three oxygen atoms . Its molecule formula is O3.

Ozone is formed when the sunlight hits oxygen molecules (O2) and breaks them up into individual atoms. These individual atoms then join up with O2 molecules and make O3, or ozone. What is the ozone layer? Way up high in the Earth's atmosphere , called the stratosphere, there is a fairly high concentration of ozone molecules that are formed when the sun hits oxygen molecules. This part of the atmosphere is called the ozone layer. Ozone is formed in the atmosphere from oxygen molecules Why is the ozone layer important? Ozone molecules in the atmosphere provide us with important protection from the rays of the sun. Specifically, these molecules are good at absorbing certain ultraviolet rays that can cause sunburn and skin cancer. How is the ozone layer getting damaged? It turns out that certain types of molecules can cause a chemical reaction when they come in contact with ozone molecules. This causes the ozone to break up and become unable to absorb ultraviolet light. The main molecules that are destroying the ozone layer are called chlorofluorocarbons or CFCs.

Chlorofluorocarbons (CFCs) Chlorofluorocarbons are a group of chemicals which are made up of only chlorine , fluorine , carbon , and hydrogen . They were first used as refrigerants to keep things cold. A lot of people considered CFCs miracle chemicals. Eventually they were used in a variety of products including air conditioners, spray cans, fire extinguishers, and in manufacturing foams. Unfortunately, CFCs can eventually find their way into the Earth's atmosphere and the ozone layer. Once they get there they destroy ozone molecules and cause the ozone layer to become depleted or thinner. CFCs Get Banned In 1974 scientists Sherry Rowland and Mario Molina discovered the link between the depletion of the ozone layer and CFCs. CFCs became somewhat regulated, but it wasn't until 1987 that a treaty was formed called Montreal Protocol to try and stop the manufacture and use of CFCs throughout the world. CFCs were to be banned and completely eliminated in developing countries by the year 2000.

A hole in the ozone over the Antarctic Effects on Health Because CFCs last so long, the ozone layer will likely continue to thin for some time in the future. This will cause an increase risk of sunburn and skin cancer . Skin cancer can be very dangerous. For this reason you should always wear sunscreen to protect your skin when you are outside in the sun for a long time. Strong ultraviolet rays can also damage your eyes. You can protect them by wearing sunglasses. What can we do about it? There isn't much we can do about the CFCs that were released prior to the ban, but there are some things we can do: Old refrigerators - If you have a refrigerator made before 1995 it probably uses refrigerant made from CFCs. Get a new refrigerator and be sure to have the old one disposed of properly. Air conditioning - Old air conditioners, made before 1994, typically used a CFC called Freon. If you still have one of these, it's time to get rid of it and buy a new one. Even newer air conditioners use chemicals called HCFCs.

Even though HCFCs are better for the ozone, they still contributes to the depletion, so try and use as little air conditioning as possible. Foam - A lot of foam products contain CFCs. Try and use different packing materials such as crumpled old newspapers. Facts About the Ozone Layer The word "ozone" means smelly in Greek because the gas has a strong odor. CFC molecules are highly stable and can last for up to 100 years. Unfortunately, this gives them plenty of time to find their way to the ozone layer. One chlorine molecule from a CFC can destroy up to 100,000 ozone molecules. Ultraviolet rays can also have bad effects on nature. They can kill plankton, which is a major source of food in the ocean's food chain. The ozone layer over Antarctica is very thin. It is sometimes called the "hole" in the ozone layer. Environmental Issues ESRL Global Monitoring Division - Halocarbons and other Atmospheric Trace Species Chlorofluorocarbons (CFCs) Chlorofluorocarbons (CFCs) (published in The Chapman & Hall Encyclopedia of Environmental Science, edited by David E. Alexander and Rhodes W.

Fairbridge, pp pp.78-80, Kluwer Academic, Boston, MA, 1999.) James W. Elkins National Oceanic and Atmospheric Administration (NOAA), Climate Monitoring and Diagnostics Laboratory (CMDL), 325 Broadway, Boulder, CO 80303 U.S.A. E-mail: James.W.Elkins@noaa.gov , Phone: (303) 497-6224, Fax: (303) 497-6290 Chlorofluorocarbons (CFCs) are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine. They are used in the manufacture of aerosol sprays, blowing agents for foams and packing materials, as solvents, and as refrigerants. CFCs are classified as halocarbons, a class of compounds that contain atoms of carbon and halogen atoms. Individual CFC molecules are labeled with a unique numbering system. For example, the CFC number of 11 indicates the number of atoms of carbon, hydrogen, fluorine, and chlorine (e.g. CCl3F as CFC-11).

The best way to remember the system is the "rule of 90" or add 90 to the CFC number where the first digit is the number of carbon atoms (C), the second digit is the number of hydrogen atoms (H), and the third digit is number of the fluorine atoms (F). The total number of chlorine atoms (Cl) are calculated by the expression: Cl = 2(C+1) - H - F. In the example CFC-11 has one carbon, no hydrogen, one fluorine, and therefore 3 chlorine atoms. Refrigerators in the late 1800s and early 1900s used the toxic gases, ammonia (NH3), methyl chloride (CH3Cl), and sulfur dioxide (SO2), as refrigerants. After a series of fatal accidents in the 1920s when methyl chloride leaked out of refrigerators, a search for a less toxic replacement begun as a collaborative effort of three American corporations- Frigidaire, General Motors, and Du Pont. CFCs were first synthesized in 1928 by Thomas Midgley, Jr.

of General Motors, as safer chemicals for refrigerators used in large commercial appilications 1 . Frigidaire was issued the first patent, number 1,886,339, for the formula for CFCs on December 31, 1928. In 1930, General Motors and Du Pont formed the Kinetic Chemical Company to produce Freon (a Du Pont tradename for CFCs) in large quantities. By 1935 Frigidaire and its competitors had sold 8 million new refrigerators in the United States using Freon-12 (CFC-12) made by the Kinetic Chemical Company and those companies that were licensed to manufacture this compound. In 1932 the Carrier Engineering Corporation used Freon-11 (CFC-11) in the worldís first self-contained home air-conditioning unit, called the "Atmospheric Cabinet".; Because of the CFC safety record for nontoxicity, Freon became the preferred coolant in large air-conditioning systems. Public health codes in many American cities were revised to designate Freon as the only coolant that could be used in public buildings.

After World War II, CFCs were used as propellants for bug sprays, paints, hair conditioners, and other health care products. During the late 1950s and early 1960s the CFCs made possible an inexpensive solution to the desire for air conditioning in many automobiles, homes, and office buildings. Later, the growth in CFC use took off worldwide with peak, annual sales of about a billion dollars (U.S.) and more than one million metric tons of CFCs produced. Whereas CFCs are safe to use in most applications and are inert in the lower atmosphere, they do undergo significant reaction in the upper atmosphere or stratosphere. In 1974, two University of California chemists, Professor F. Sherwood Rowland and Dr. Mario Molina, showed that the CFCs could be a major source of inorganic chlorine in the stratosphere following their photolytic decomposition by UV radiation. In addition, some of the released chlorine would become active in destroying ozone in the stratosphere 2 . Ozone is a trace gas located primarily in the stratosphere (see ozone).

Ozone absorbs harmful ultraviolet radiation in the wavelengths between 280 and 320 nm of the UV-B band which can cause biological damage in plants and animals. A loss of stratospheric ozone results in more harmful UV-B radiation reaching the Earth's surface. Chlorine released from CFCs destroys ozone in catalytic reactions where 100,000 molecules of ozone can be destroyed per chlorine atom. A large springtime depletion of stratospheric ozone was getting worse each following year. This ozone loss was described in 1985 by British researcher Joe Farman and his colleagues 3 . It was called ìthe Antarctic ozone holeî by others. The ozone hole was different than ozone loss in the midlatitudes. The loss was greater over Antarctic than the midlatitudes because of many factors: the unusually cold temperatures of the region, the dynamic isolation of this ìholeî, and the synergistic reactions of chlorine and bromine 4 . Ozone loss also is enhanced in polar regions as a result of reactions involving polar stratospheric clouds (PSCs) 5 and in midlatitudes following volcanic eruptions. The need for controlling the CFCs became urgent.

In 1987, 27 nations signed a global environmental treaty, the Montreal Protocol to Reduce Substances that Deplete the Ozone Layer 6 , that had a provision to reduce 1986 production levels of these compounds by 50% before the year 2000. This international agreement included restrictions on production of CFC-11, -12, -113, -114, -115, and the Halons (chemicals used as a fire extinguishing agents). An amendment approved in London in 1990 was more forceful and called for the elimination of production by the year 2000. The chlorinated solvents, methyl chloroform (CH3CCl3), and carbon tetrachloride (CCl4) were added to the London Amendment.

Large amounts of reactive stratospheric chlorine in the form of chlorine monoxide (ClO) that could only result from the destruction of ozone by the CFCs in the stratosphere were observed by instruments onboard the NASA ER-2 aircraft and UARS (Upper Atmospheric Research Satellite) over some regions in North America during the winter of 1992 7,8 . The environmental concern for CFCs follows from their long atmospheric lifetime (55 years for CFC-11 and 140 years for CFC-12, CCl2F2) 9 which limits our ability to reduce their abundance in the atmosphere and associated future ozone loss. This resulted in the Copenhagen Amendment that further limited production and was approved later in 1992. The manufacture of these chemicals ended for the most part on January 1, 1996. The only exceptions approved were for production within developing countries and for some exempted applications in medicine (i.e., asthma inhalators) and research. The Montreal Protocol included enforcement provisions by applying economic and trade penalties should a signatory country trade or produce these banned chemicals. A total of 148 signatory countries have now signed the Montreal Protocol.

Atmospheric measurements CFC-11 and CFC-12 reported in 1993 showed that their growth rates were decreasing as result of both voluntary and mandated reductions in emissions 9 . Many CFCs and selected chlorinated solvents have either leveled off (Figure 1) or decreased in concentration by 1994 9,10 . The demand for the CFCs was accomodated by recycling, and reuse of existing stocks of CFCs and by the use of substitutes. Some applications, for example degreasing of metals and cleaning solvents for circuit boards, that once used CFCs now use halocarbon-free fluids, water (sometimes as steam), and diluted citric acids. Industry developed two classes of halocarbon substitutes- the hydrochlorofluorocarbons (HCFCs) and the hydrofluorocarbons (HFCs). The HCFCs include hydrogen atoms in addition to chlorine, fluorine, and carbon atoms. The advantage of using HCFCs is that the hydrogen reacts with tropospheric hydroxyl (OH), resulting in a shorter atmospheric lifetime.

HCFC-22 (CHClF2) has an atmospheric lifetime of about 13 years 11 and has been used in low-demand home air-conditioning and some refrigeration applications since 1975. However, HCFCs still contain chlorine which makes it possible for them to destroy ozone. The Copenhagen amendment calls for their production to be eliminated by the year 2030. The HFCs are considered one of the best substitutes for reducing stratospheric ozone loss because of their short lifetime and lack of chlorine. In the United States, HFC-134a is used in all new domestic automobile air conditioners. For example, HFC-134a is growing rapidly in 1995 at a growth rate of about 100% per year with an atmospheric lifetime of about 12 years 12 . (The "rule of 90" also applies for the chemical formula of HCFCs and HFCs.) Use of the CFCs, some chlorinated solvents, and Halons should become obsolete in the next decade if the Montreal Protocol is observed by all parties and substitutes are used.

The science that became the basis for the Montreal Protocol resulted in the 1995 Nobel Prize for Chemistry. The prize was awarded jointly to Professors F. S. Rowland at University of California at Irvine, M. Molina at the Massachusetts Institute of Technology, Cambridge, and Paul Crutzen at the Max-Planck-Institute for Chemistry in Mainz, Germany, for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone (in particular, by the CFCs and oxides of nitrogen). 1 Midgley, T., and Henne, A., Organic fluorides as refrigerants, Industrial and Engineering Chemistry, 22, 542-547, 1930. 2 Molina, M.J., and F.S. Rowland, Stratospheric sink for chlorofluoromethanes: Chlorine atom catalyzed destruction of ozone, Nature, 249, 810-814, 1974. 3 Farman, J.C., B.G. Gardiner, and J.D.

Shanklin, Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction, Nature, 315,207-210, 1985. 4 McElroy, M.B., R.J. Salawitch, S.C. Wofsy, and J.A. Logan, Reductions of Antarctic ozone due to synergistic interactions of chlorine and bromine, Nature, 321, 759-762, 1986. 5 Solomon, S., R.R. Garcia, F.S. Rowland, and D.J. Wuebbles, On the depletion of Antarctic ozone, Nature, 321, 755-758, 1986. 6 Montreal Protocol on Substances that Deplete the Ozone Layer, 15 pp, United Nations Environmental Programme (UNEP), New York, 1987. 7 Toohey, D.W., L.M. Avallone, L.R. Lait, P.A. Newman, M.R. Schoeberl, D.W. Fahey, E.L. Woodbridge, and J.G.

Anderson, The seasonal evolution of reactive chlorine in the northern hemisphere stratosphere, Science, 261, 1134-1136, 1993. 8 Waters, J., L. Froidevaux, W. Read, G. Manney, L. .Elson, D. Flower, R. Jarnot, and R. Harwood, Stratospheric ClO andozone from the Microwave Limb Sounder on the Upper Atmosphere Research Satellite, Nature, 362, 597-602, 1993. 9 Elkins, J.W., T.M. Thompson, T.H. Swanson, J.H. Butler, B.D. Hall, S.O. Cummings, D.A. Fisher, and A.G. Raffo, Decrease in the growth rates of atmospheric chlorofluorocarbons 11 and 12, Nature, 364 , 780-783, 1993. 10 Prinn, R.G., R.F. Weiss, B.R. Miller, J. Huang, F.N.

Alyea, D.M. Cunnold, P.J. Fraser, D.E. Hartley, and P.G. Simmonds, Atmospheric trends and lifetimes of CH3CCl3 and global OH concentrations, Science, 269, 187-192, 1995. 11 Montzka, S.A., R.C. Myers, J.H. Butler, S.C. Cummings, and J.W. Elkins, Global tropospheric distribution and calibration scale of HCFC-22, Geophysical Research Letters, 20 (8), 703-706, 1993. 12 Montzka, S.A., R.C. Myers, J.H. Butler, J.W. Elkins, L.T. Lock, A.D. Clarke, and A.H. Goldstein, Observations of HFC-134a in the remote troposphere, Geophysical Research Letters, 23, 169-172, 1996. Suggested Additional Reading: Cagin, S., and P.

Dray, Between Earth and Sky: How CFCs changed our world and threatened the ozone layer, 512 pp., Pantheon Press, New York, 1993. Scientific Assessment of Ozone Depletion: 1994, edited by D. L. Albritton, R. T. Watson, and R. J. Aucamp, 37, 451 pp., World Meteorological Organization (WMO), Geneva, 1995. Figure 1: The accumulation of chlorofluorocarbon-11 (CFC-11) in the atmosphere levels off as a result of voluntary and mandated emission reductions. Monthly means reported as dry mixing ratios in parts per trillion (ppt) for CFC-11 at ground level for four NOAA/CMDL stations (Pt.

Barrow, Alaska; Mauna Loa, Hawaii; Cape Matatula, American Samoa; and South Pole) and three cooperative stations (Alert, Northwest Territories, Canada (Atmospheric Environment Service); Niwot Ridge, Colorado (University of Colorado); Cape Grim Baseline Air Pollution Station, Tasmania, Australia, (Commonwealth Scientific and Industrial Research Organization) 9 Ozone Depletion | Chlorofluorcarbons | CFCs | Stratospheric Ozone Chlorofluorcarbons Introduction Man-made CFCs are the main cause of stratospheric ozone depletion. CFCs have a lifetime of about 20 to 100 years, and consequently one free chlorine atom from a CFC molecule can do a lot of damage, destroying ozone molecules for a long time. Although emissions of CFCs around the developed world have largely ceased due to international control agreements, the damage to the stratospheric ozone layer will continue for a number of years to come. What are CFCs? Chlorofluorocarbons or CFCs (also known as freon) are non-toxic, non-flammable and non-carcinogenic. They contain 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). Use of CFCs In the past, CFCs have been widely used as coolants in refrigeration and air conditioners, as solvents in cleaners, particularly for electronic circuit boards, as a blowing agents in the production of foam (e.g. fire extinguishers), and as propellants in aerosols. Indeed, much of the modern lifestyle of the mid-20th century had been made possible by the use of CFCs. The pie chart below shows the uses of CFCs in various products before the 1987 Montreal Protocol, which required countries to phase out their usage to protec the ozone layer.

No new CFCs have been produced since 1995 in developed nations. Total usage of CFCs has also fallen dramatically, particularly by aerosols. The only aerosols using CFCs in the developed world are asthma inhalers and these too are being phased out. Aerosol propellants now use only 4.9% of total use of CFC-11 and CFC-12 in the world today. How do CFCs Destroy the Ozone Layer? Emissions of CFCs to date have accounted for roughly 80% of total stratospheric depletion. Whilst chlorine is a natural threat to ozone, CFCs which contain chlorine are a man-made problem. Although CFC molecules are several times heavier than air, winds mix the atmosphere to altitudes far above the top of the stratosphere much faster than molecules can settle according to their weight. CFCs are insoluble in water and relatively unreactive in the lower atmosphere but are quickly mixed and reach the stratosphere regardless of their weight. When UV radiation hits a CFC molecule it causes one chlorine atom to break away.

The chlorine atom then hits an ozone molecule consisting of three oxygen atoms and takes one of the oxygen molecules, destroying the ozone molecule and turning it into oxygen. When an oxygen molecule hits the molecule of chlorine monoxide, the two oxygen atoms join and form an oxygen molecule. When this happens, the chlorine atom is free and can continue to destroy ozone. Naturally occurring chlorine has the same effect in the ozone layer, but has a shorter life span. Control of CFCs Since 1995, emissions of new CFCs in the developed world have been completely phased out. As evidence accumulated that man-made CFCs were contributing to stratospheric ozone depletion, scientists urged nations to control the use of CFCs. In 1987, the Montreal Protocol on Substances that Deplete the Ozone Layer was negotiated and signed by 24 countries. The Protocol called for the parties to phase down the use of CFCs, as well as other ozone depleting chemicals such as halons and other man-made halocarbons.

Although emissions of CFCs have fallen dramatically as a result of the Montreal Protocol, because each chlorine molecule remains in the atmosphere for such a long time, damage done to stratospheric ozone will persist for many years to come. ESRL Integrating Research and Technology Themes 20 Questions and Answers About Ozone What do we know about ozone depletion and recovery? The stratospheric ozone layer has become substantially depleted throughout much of the globe since the 1980s because of enhanced human production and use of ozone- depleting chemicals, such as chlorofluorocarbons, halons, and others, during the 20th century. UV radiation increases in areas where the ozone layer has thinned. Ozone-depleting chemicals include those that contain chlorine or bromine and that are not easily removed from the atmosphere by chemical degradation or dissolution in clouds and rain. Atmospheric observations of these chemicals during the latter part of the 20th century showed dramatic increases that could be directly traced to the amounts produced by humans. By 1980, the amounts of chlorine and bromine from these chemicals soon far surpassed the smaller amounts of atmospheric chlorine and bromine arising from natural processes.

The abnormally high quantities of atmospheric chlorine and bromine began altering the balance of ozone in the stratosphere so as to dramatically thin the ozone layer. Since the 1980s the most severe ozone layer depletion has been regularly observed over Antarctica during spring, when ozone levels drop by over 95% and UV radiation reaching Earth's surface increases substantially. Less intense depletion of ozone occurs above the Arctic and in mid-latitudes of both hemispheres. Source: Scientific Assessment of Ozone Depletion: 2002 , World Meteorological Organization, Global Ozone Research and Monitoring Project, Report No. 47 Global total ozone changes. Global total ozone values decreased by an average of a few percent in the last two decades, as measured by satellite instruments. In the top panel, global ozone changes are compared with average global ozone found in the period of 1964 to 1980. Between 1980 and 2000, the largest decreases occurred following the volcanic eruption of Mt. Pinatubo in 1991.

In the 1997 to 2001 period global ozone was reduced by about 3% from the 1964- 1980 average. In the bottom panel, ozone changes between 1980 and 2000 are compared for different latitudes. The largest decreases have occurred at the highest latitudes in both hemispheres because of the large winter/spring depletion in polar regions. The losses in the Southern Hemisphere are greater than those in the Northern Hemisphere because of the greater losses that occur each year in the Antarctic stratosphere. Long-term changes in the tropics are much smaller because reactive halogen gases are not abundant in the tropical lower stratosphere. As a result of the discovery of ozone depletion and the scientific advances that delineated its causes, efforts to reduce the production, and ultimately the atmospheric concentrations, of ozone-depleting chemicals were begun in the late 1980s through the ratification of the Montreal Protocol on Substances that Deplete the Ozone Layer by many countries across the globe. This international Protocol and its subsequent revisions and amendments have resulted in a turnaround in the atmospheric abundance of most ozone-depleting chemicals.

While atmospheric levels of ozone-depleting chemicals were rapidly increasing before the Protocol was ratified, emissions of nearly all of these chemicals have declined substantially and atmospheric levels of most of these gases have decreased in the intervening 2 decades. Measurements show that depletion of the ozone layer steadily worsened during the 1980s and most of the 1990s, but more recently as atmospheric amounts of chlorine and bromine have stabilized, a further worsening of ozone depletion appears to have been avoided. In the mid-latitude stratosphere, for example, the decreases in the ozone layer seen in the 1980s and 1990s have not continued. Continued declines in ozone-depleting gases are expected to allow for a recovery of the ozone layer, but not until the middle of the 21st century. The long time scale for this recovery arises because ozone depleting gases such as chlorofluorocarbons are only removed from the atmosphere by natural processes at very slow rates. Source: Scientific Assessment of Ozone Depletion: 2002 , World Meteorological Organization, Global Ozone Research and Monitoring Project, Report No. 47 Halogen source gas changes.

The rise in effective stratospheric chlorine values in the 20th century has slowed and reversed in the last decade (top panel). Effective chlorine values combine the measured or projected abundances of chlorine-containing gases with those of brominecontaining gases in a way that properly accounts for the greater effectiveness of bromine in depleting stratospheric ozone. As effective chlorine decreases in the 21st century, the potential for ozone depletion from halogen gases will also decrease. The decrease in effective chlorine values is a result of reductions in individual halogen source gas emissions. The emissions decreased because of the Montreal Protocol, which restricts production and consumption of manufactured halogen gases. The changes in the atmospheric abundance of individual gases are shown in the lower panels using a combination of direct atmospheric measurements, estimates of historical abundance, and future projections of abundance. The increases of CFCs, along with those of CCl4 and CH3CCl3, have either slowed significantly or reversed in the last decade. HCFCs, which are being used as CFC substitutes, will continue to increase in the coming decades. Some halon abundances will also grow in the future while current halon reserves are being depleted.

Smaller relative decreases are expected for CH3Br in response to restrictions because it has substantial natural sources. CH3Cl has large natural sources and is not regulated under the Montreal Protocol. Contributions to International Efforts Pollutant Fact Sheet Pollutant Emissions to Air Disclaimer This sheet is a generic summary, designed to give the reader a basic level of background information about the substance in question. Great care has been taken to represent as effectively and correctly as possible the broad range of (not necessarily consistent) information which is available from a variety of sources. The reader must accept therefore that this sheet has no legal status and cannot be relied upon in any legal proceedings. SEPA disclaims any responsibility or liability whatsoever for errors and omissions in this sheet. What is it? Chlorofluorocarbons (CFCs) are a group of compounds which contain the elements chlorine, fluorine and carbon. At room temperatures, they are usually colourless gases or liquids which evaporate easily. They are generally unreactive and stable, non-toxic and non-flammable. CFCs are also a part of the group of chemicals known as the volatile organic compounds (VOCs). What is it used for?

The properties of CFCs make them useful for a variety of commercial and industrial purposes: as a propellant in aerosol sprays (now banned in the US and Europe), in refrigeration and air conditioning systems, in foams, in cleaning solvents and in electrical components. Where does it come from? Most CFCs have been released to the atmosphere through the use of aerosols containing them and as leakages from refrigeration equipment. Other releases may occur from industry producing and using them and other products containing them. There are not thought to be any natural sources of CFCs to the environment. How might it affect the environment? CFCs are unlikely to have any direct impact on the environment in the immediate vicinity of their release. As VOCs, they may be slightly involved in reactions to produce ground level ozone, which can cause damage to plants and materials on a local scale. At a global level however, releases of CFCs have serious environmental consequences. Their long lifetimes in the atmosphere mean that some end up in the higher atmopshere (stratosphere) where they can destroy the ozone layer, thus reducing the protection it offers the earth from the sun's harmful UV rays.

CFCs also contribute to Global Warming (through "the Greenhouse Effect"). Although the amounts emitted are relatively small, they have a powerful warming effect (a very high "Global Warming Potential"). How might exposure to it affect human health? Chlorofluorocarbons enter the body primarily by inhalation of air containing chlorofluorocabons, but can also enter by ingestion of contaminated water, or by dermal contact with chlorofluorocarbons. Inhalation of high levels of chlorofluorocarbons can affect the lungs, central nervous system, heart, liver and kidneys. Symptoms of exposure to chlorofluorocarbons can include drowsiness, slurred speech, disorientation, tingling sensations and weakness in the limbs. Exposure to extremely high levels of chlorofluorocarbons can result in death. Ingestion of chlorofluorocarbons can lead to nausea, irritation of the digestive tract and diarrhoea. Dermal contact with chlorofluorocarbons can cause skin irritation and dermatitis.

Chlorofluorocarbons are involved in the destruction of the stratospheric ozone layer resulting in increased exposure to UV radiation which is known to cause skin cancer. The International Agency for Research on Cancer has not designated chlorofluorocarbons as a group in terms of their carcinogenicity. The International Agency for Research on Cancer has designated chlorofluoromethane and chlorodifluoromethane as being not classifiable as to their carcinogenicity to humans. However, exposure to chlorofluorocarbons at normal background levels is unlikely to have any adverse effect on human health. What steps are being taken to limit the potential impacts? The main legislation controlling releases of CFCs is the Montreal Protocol, which came into force in 1987. This is an international agreement which obliged most signaturies to completely phase out their use of CFCs by 1996. Only developing countries were allowed to exceed this at a level of up to 15% of their production pre the signing of the Protocol. Releases in the UK are also controlled through the UK Pollution, Prevention and Control (PPC) Regulations.

Chlorofluorocarbon | Definition of Chlorofluorocarbon by Merriam-Webster Definition of chlorofluorocarbon : any of several simple gaseous compounds that contain carbon, chlorine , fluorine, and sometimes hydrogen, that are used as refrigerants, cleaning solvents, and aerosol propellants and in the manufacture of plastic foams, and that are believed to be a major cause of stratospheric ozone depletion —abbreviation CFC All About Ozone All About Ozone Source: The Environmental Protection Agency I. The Ozone Layer The Earth's atmosphere is divided into several layers. The lowest region, the troposphere, extends from the Earth's surface up to about 10 kilometers (km) in altitude. The next layer, the stratosphere, continues from 10 km to about 50 km. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 15–30 kilometers above the Earth's surface. Ozone is a molecule containing three oxygen atoms. It is blue in color and has a strong odor. Normal oxygen, which we breathe, has two oxygen atoms and is colorless and odorless. Ozone is much less common than normal oxygen.

Out of each 10 million air molecules, about 2 million are normal oxygen, but only 3 are ozone. However, even the small amount of ozone plays a key role in the atmosphere. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface. Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects, including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life. At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount, however, remains relatively stable. While ozone concentrations vary naturally with sunspots, the seasons, and latitude, these processes are well understood and predictable. Each natural reduction in ozone levels has been followed by a recovery. Recently, however, convincing scientific evidence has shown that the ozone shield is being depleted well beyond changes due to natural processes. II. Ozone Depletion For over 50 years, chlorofluorocarbons, or CFCs, were thought of as miracle substances. They are stable, nonflammable, low in toxicity, and inexpensive to produce.

Over time, CFCs found uses as refrigerants, solvents, foam blowing agents, and in other smaller applications. Other chlorine-containing compounds include methyl chloroform, a solvent, and carbon tetrachloride, an industrial chemical. Halons, extremely effective fire extinguishing agents, and methyl bromide, an effective produce and soil fumigant, contain bromine. All of these compounds have atmospheric lifetimes long enough to allow them to be transported by winds into the stratosphere. Because they release chlorine or bromine when they break down, they damage the protective ozone layer. In the early 1970s, researchers began to investigate the effects of various chemicals on the ozone layer, particularly CFCs, which contain chlorine. They also examined the potential impacts of other chlorine sources. Chlorine from swimming pools, industrial plants, sea salt, and volcanoes does not reach the stratosphere. Chlorine compounds from these sources readily combine with water and repeated measurements show that they rain out of the troposphere very quickly. In contrast, CFCs are very stable and do not dissolve in rain. Thus, there are no natural processes that remove the CFCs from the lower atmosphere.

Over time, winds drive the CFCs into the stratosphere. The CFCs are so stable that only exposure to strong UV radiation breaks them down. When that happens, the CFC molecule releases atomic chlorine. One chlorine atom can destroy over 100,000 ozone molecules. The net effect is to destroy ozone faster than it is naturally created. III. Ozone FAQ What is the ozone layer and why is it important? The ozone layer is a concentration of ozone molecules in the stratosphere. About 90% of the planet's ozone is in the ozone layer. The layer of the Earth's atmosphere that surrounds us is called the troposphere. The stratosphere, the next higher layer, extends about 10–50 kilometers above the Earth's surface. Stratospheric ozone is a naturally occurring gas that filters the sun's ultraviolet (UV) radiation. A diminished ozone layer allows more radiation to reach the Earth's surface. For people, overexposure to UV rays can lead to skin cancer, cataracts, and weakened immune systems. Increased UV can also lead to reduced crop yield, disruptions in the marine food chain, and other harmful effects. How does ozone depletion occur?

It is caused by the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents. The discussion below focuses on CFCs, but is relevant to all ODS. Although CFCs are heavier than air, they are eventually carried into the stratosphere in a process that can take as long as 2 to 5 years. When CFCs reach the stratosphere, the ultraviolet radiation from the sun causes them to break apart and release chlorine atoms, which react with ozone, starting chemical cycles of ozone destruction that deplete the ozone layer. One chlorine atom can break apart more than 100,000 ozone molecules. Other chemicals that damage the ozone layer include methyl bromide (used as a pesticide) and halons (used in fire extinguishers). As methyl bromide and halons are broken apart, they release bromine atoms, which are 40 times more destructive to ozone molecules than chlorine atoms. How do we know that natural sources are not responsible for ozone depletion?

While it is true that volcanoes and oceans release large amounts of chlorine, the chlorine from these sources is easily dissolved in water and washes out of the atmosphere in rain. In contrast, CFCs are not broken down in the lower atmosphere and do not dissolve in water. The chlorine in these human-made molecules does reach the stratosphere. Measurements show that the increase in stratospheric chlorine since 1985 matches the amount released from CFCs and other ozone-depleting substances produced and released by human activities. What is being done about ozone depletion? In 1978, the use of CFC propellants in spray cans was banned in the U.S. In the 1980s, the Antarctic “ozone hole” appeared and an international science assessment more strongly linked the release of CFCs and ozone depletion. It became evident that a stronger worldwide response was needed. In 1987, the Montreal Protocol was signed and the signatory nations committed themselves to a reduction in the use of CFCs and other ozone-depleting substances. Since that time, the treaty has been amended to ban CFC production after 1995 in the developed countries, and later in developing.

Today, over 160 countries have signed the treaty. Beginning January 1, 1996, only recycled and stockpiled CFCs will be available for use in developed countries like the US. This production phaseout is possible because of efforts to ensure that there will be substitute chemicals and technologies for all CFC uses. Will the ozone layer recover? Can we make more ozone to fill in the hole? The answers, in order, are: yes and no. We can't make enough ozone to replace what's been destroyed, but provided that we stop producing ozone-depleting substances, natural ozone production reactions should return the ozone layer to normal levels by about 2050. It is very important that the world comply with the Montreal Protocol; delays in ending production could result in additional damage and prolong the ozone layer's recovery.

Question: What atmospheric layer is damaged by chlorofluorocarbons?
Answer: Ozone Layer