CFCs and Ozone Depletion

Enlarge Image Image Gallery Ozone-depleting CFC products: furniture cushion foam, extruded polystyrene foam insulation (boards on the floor), polyisocyanurate foam (in background), auto air conditioner, refrigerator, halon fire extinguisher, photographic dust remover, auto air conditioner recharge kit, and foam sealant. PHOTO: MICHAEL SOLURI

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.