GETTING BY WITHOUT CFA's

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The ozone hole over Antarctica, and now a thinning of the ozone layer above the Arctic, has led to worldwide action to curtail the use of the primary culprits: CFCs and related compounds called halons. These chemicals introduce chlorine and several other reactive elements into the stratosphere 15 to 50 kilometers above the earth's surface. There, the chlorine ions react with ozone, breaking off one of the three oxygen atoms and forming a transition compound, chlorine monoxide, and molecular oxygen (see Fig. 1). The chlorine monoxide in turn reacts with another ozone molecule, repeating the process. A single chlorine atom can break down tens of thousands of ozone molecules in this manner.

Because ozone blocks out harmful ultraviolet light, the resultant thinning of the ozone layer is a big concern to life on earth. With the protective barrier gone, high-energy UV-B radiation reaches earth, where it could wreak havoc. Among the human health effects of UV-B radiation are acute sunburn, skin cancer, cataracts and other eye disorders, and possible suppression of the immune system. UV-B radiation could also reduce agricultural crop yields, kill organisms in the highly productive top layer of the ocean, exacerbate smog in some urban areas, and speed the degradation of paints, plastics, and other manmade materials.

CFCs are able to introduce chlorine to the stratosphere primarily because the chemicals are so stable. Most gaseous compounds readily break down within a period of days or weeks when released into the air, but CFCs are highly stable-some lasting more than 100 years. Over a period of years or decades, winds carry the CFCs up into the stratosphere, where the high-energy UV-B radiation has enough power to break them apart, as described.

Ironically, it is this tremendous stability that made CFCs such valuable industrial chemicals. Being stable, they don't react with refrigerator coils or electronic circuit boards, they remain nonflammable, and they are nontoxic. On top of that, they are inexpensive to produce and exhibit a wide range of highly desirable properties for use in manufacturing and refrigeration. As an example of the durability of these chemicals, a refrigerator charged with CFC refrigerant in the 1950s could still be using the same fluid today, more than 30 years later. Because of this, the CFC industry, which was born around 1920, grew into a multibillion-dollar industry by the 1980s, with 700 million pounds produced in 1986.

Intense concern over ozone depletion and CFCs has led to unprecedented international action to reduce the production and use of CFCs and halons (which are used in fire extinguishing systems). In September 1987, 24 nations and the European Economic Community met in Montreal and signed a treaty, Substances That Deplete the Ozone Layer. The agreement, which took effect after the necessary number of countries ratified it, limits annual consumption of five CFCs (CFC11, -12, -113, -114, and -115) to 1986 levels starting July 1, 1989. This represents about a 20% reduction from 1988 levels, because of recent growth in CFC use. Reductions to 80% and 50% of 1986 levels will occur in 1993 and 1998, respectively. Helena are regulated separately from CFCs. Starting in 1992, halon consumption will be frozen at 1986 levels.

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