In , the Montreal Protocol on Substances that Deplete the Ozone Layer set a formal timetable for the phase-out of Freon and other ozone-depleting compounds. See Reference 7, Pages 7 and 8 Under this international treaty, which has been ratified by more than nations, most CFC production ceased by ; production of hydrochlorofluorocarbons -- which were originally created as an environmentally preferable substitute for CFCs -- is scheduled to end by See Reference 10, Pages 4, 18 and 19 The U.
Environmental Protection Agency estimates that by ozone will return to s levels, and projects that the associated reduction in skin cancer will save 6. See Reference 10, Pages 5 and 7 The Montreal Protocol also made a significant contribution to the fight against global warming, since many ozone-depleting chemicals also act as greenhouse gases.
See Reference 10, Page 33 In addition, it demonstrated that scientists, governments and businesses from all over the world could collaborate effectively to address global environmental problems.
See Reference 10, Pages 14 to David Swan has been a professional writer since , working primarily on academic titles. He has written and edited textbooks on green business, community redevelopment and the chemistry of hazardous materials.
Does Freon Really Affect the Ozone? By David Swan. Ozone and nitrate radicals are even less effective at breaking down CFCs. Sherwood Rowland of the University of California at Irvine, who won a Nobel Prize for his work on atmospheric chemistry, answers: "This is indeed a persistent question--so much so that the most recent report of the World Meteorological Organization, entitled 'Scientific Assessment of Ozone Depletion: ,' included it among a list of common questions that have been persistently raised and long since answered.
We had as many as 22 of them, but pared them down to the most frequently asked ones. Although the CFC molecules are indeed several times heavier than air, thousands of measurements have been made from balloons, aircraft and satellites demonstrating that the CFCs are actually present in the stratosphere. The atmosphere is not stagnant. Winds mix the atmosphere to altitudes far above the top of the stratosphere much faster than molecules can settle according to their weight.
Gases such as CFCs that are insoluble in water and relatively unreactive in the lower atmosphere below about 10 kilometers are quickly mixed and therefore reach the stratosphere regardless of their weight. Much can be learned about the atmospheric fate of compounds from the measured changes in concentration versus altitude. For example, the two gases carbon tetrafluoride CF 4 , produced mainly as a by-product of the manufacture of aluminum and CFC CCl 3 F, used in a variety of human activities are both much heavier than air.
Carbon tetrafluoride is completely unreactive in the lower There have also been measurements over the past two decades of several other completely unreactive gases, one lighter than air neon and some heavier than air argon, krypton , which show that they also mix upward uniformly through the stratosphere regardless of their weight, just as observed with carbon tetrafluoride. CFC is unreactive in the lower atmosphere below about 15 kilometers and is similarly uniformly mixed there, as shown.
The abundance of CFC decreases as the gas reaches higher altitudes, where it is broken down by high energy solar ultraviolet radiation. Chlorine released from this breakdown of CFC and other CFCs remains in the stratosphere for several years, where it destroys many thousands of molecules of ozone. The uniform mixing of CF4 versus altitude was reported from balloons around and many times since, and from an infrared instrument aboard the space shuttle Challenger which exploded in in One of the natural refrigerants such as hydrocarbons mixed with Ammonia and Carbon Dioxide do not have a damaging effect on the environment and are used in commercial and private applications.
Early refrigeration products from the late 19th century to the early 20th century used toxic gases like ammonia NH3 , methyl chloride CH3CI , and sulfur dioxide SO2. This sometimes caused fatalities from leakage of these products. This is the reason many people placed their refrigerator in the back yard. It was then that large refrigeration brands like Frigidaire, General Motors and DuPont began looking for a less dangerous refrigerant compound.
In , two inventors, Thomas Midgley, Jr. This refrigerant was made with a few types of chlorofluorocarbons or CFCs. Freons are colorless, nonflammable, have no odor and offer a non-corrosive gas or liquid. They are a mix of aliphatic compounds with halogens, fluorine, and carbon. They represent a very stable product that could be placed in a spray container and was commercialized under the name of Freon.
This invention came about as a safer alternative to an earlier sulfur dioxide and ammonia refrigerant that could easily become dangerous and flammable. These compounds offered a viable way of making refrigerant products that were non-flammable, and they were first created in the late s and were marketed as a non-toxic, non-flammable refrigerant and were first marketed by the DuPont company. The first of the compounds were known as CFC It contained one carbon and two chlorides with two fluorines CFC or F are halogenated hydrocarbons with dichlorodifluoromethane and were used as an aerosol spray propellants, refrigerants, foam blowing products and other similar solvents.
They were used in many refrigerant or insulating processes because the were non-toxic and could easily be converted to a liquid or gas to be used later in vehicles and home products.
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