CFCs and Ozone Depletion

Reduce ozone depletion and environmental pollution by decreasing your use of common products with harmful chlorofluorocarbons, and learn more about the alternatives that are already available or currently under development.


| November/December 1989



UV Light and CFC Molecule

UV light breaks a chlorine atom off a CFC molecule. The chlorine reacts with ozone (O3), forming molecular oxygen (O2) and chlorine monoxide. The oxygen is pulled off that molecule by a free oxygen atom, leaving the chlorine atom to start the process all over again.


DON OSBY

Most of us are more than willing to make a few changes in lifestyle if it's good for the environment. We're learning to get by without pesticides in the garden. More and more we drive relatively energy-efficient cars. Surveys show that most of us would even be willing to pay a little more on our electric bills if doing so would help reduce acid rain. But what about CFCs and ozone depletion? We've heard a lot about CFCs, or chlorofluorocarbons, and their destruction of the earth's protective ozone layer. How can we minimize our use of these ozone-depleting chemicals?

Chances are you're a pretty big user of CFCs. Eighty percent of cars sold in the U.S. have air conditioners—the largest single source of CFC release into the atmosphere. You almost certainly have a refrigerator in your home, with one type of CFC used as the refrigerant fluid and another in the insulation. If you've done any construction in the last few years, you probably used foam insulation and cans of spray-foam sealant containing CFCs—particularly if you were building an energy-efficient house. CFCs are also used in foam cushions, packaging materials, cleaning fluids for electronic equipment, some aerosol propellants, and many consumer products such as boat horns, tire inflators, and Dust-Off for cleaning camera lenses. This article will review where CFCs are used around the home and business and describe some of the alternatives currently available or under development.

Ozone Depletion

Concerns over ozone have generated quite a bit of confusion in recent years. Ozone is a bad guy at ground level, where high levels present a serious pollution problem in most major cities. But the same compound, a form of oxygen, is a good guy in the upper atmosphere, where it blocks out harmful ultraviolet light. Scientists first theorized 15 years ago that man-made chemicals could break down the protective ozone layer. Their warnings led to a ban of CFC aerosols in this country in 1978. After taking that action, we pretty much forgot about ozone depletion and CFCs for 10 years. All that complacency vanished, however, after scientists discovered a large hole in the ozone layer over Antarctica in 1985.

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 man-made 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.

shubhi
1/12/2008 4:03:48 AM

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