Were spray deodorants and shaving creams the serious threat they were made out to be a few years ago, or was the ban-the-can movement a prime example of environmental alarmism?
After a number of studies—each yielding some increment of information—the evidence is accumulating that the old-style spray cans and their chemical kin are indeed potentially harmful through the interaction of aerosols with stratospheric ozone. The following review will bring the reader up to date on a threat which doubtless has drawn more than its fair share of disbelievers.
Oxygen atoms in the stratosphere combine with the usual form of molecular oxygen (02) to form ozone (03), another molecular form containing three oxygen atoms. A layer of ozone in the stratosphere serves as a shield, limiting the amount of biologically damaging ultraviolet radiation that reaches the earth's surface and causes sunburn, skin cancer, and other destructive biological effects.
Ozone is continuously being formed and depleted by a number of natural chemical processes. However, about five years ago, several groups of scientists almost simultaneously discovered that additional depletion apparently occurs because of chemical reactions caused by halocarbons, a class of man-made chemicals. The halocarbons are formed by the bonding of a carbon atom to halogen atoms, where the halogens include iodine, bromine, chlorine, and fluorine.
The important halocarbons, in terms of ozone-depletion, are the chlorofluorocarbons, CFCs for short. Of these, the most important are chlorofluoromethanes, CFMs. The CFCs contain both chlorine and fluorine as well as carbon, and may contain hydrogen; the CFMs have only one carbon atom in their molecule.
A recent National Academy of Sciences report estimates that continued release of CFCs at their current rate eventually would reduce the ozone layer by some 11 to 16 percent. This, in turn, could imply considerably higher skin cancer rates (perhaps 50 percent above current rates). Most forms of skin cancer are nonfatal and relatively easy to control, but one—melanoma—often is fatal.
Biological impacts on other species also would increase, and some climate change would involve a small warming effect, increasing the global temperature by about one degree centigrade. The climate effect is directly attributable to CFCs, rather than to their indirect effect on ozone. One degree may not sound like much, but it may be in addition to several degrees of warming generated by increased atmospheric levels of carbon dioxide. The consequences could then be far-reaching. Agriculture almost certainly would be affected, and eventually there might be considerable melting of the polar ice caps and an increase in sea levels that would inundate many coastal areas.
As is now well known, a major increase of CFMs occurred because of their use in aerosol spray cans. This practice now is banned by law in the United States, but although some European nations have followed suit, most other countries have made no attempt to do so. Since melanoma affects only light-skinned people, many countries will not have much direct incentive to reduce CFC use, a potentially nasty bone of contention in future North—South dialogues. On the other hand, temperature increases can be beneficial, or at least less costly, for those living in colder climates who tend to be light-skinned.
In addition to banning aerosol sprays containing CFCs, the Environmental Protection Agency is considering regulations which will limit the use of CFCs in other products. Since CFCs are important in refrigeration, air conditioning, and plastics, important economic tradeoffs are involved.
The future use of CFCs in the United States probably will decline. Incentives for the use of substitutes will grow, reflecting even more stringent regulation plus a reduction in supplies of raw materials used in CFC manufacture which, in turn, should drive up CFC prices.
There is a good deal of uncertainty about all the chemical and biological processes involved. In the past, there have been parallel concerns about nitrogen fertilizers and high-flying airplanes, neither of which now are believed to cause much ozone depletion. Regardless, it seems clear that the halocarbon—ozone connection has the potential for considerable irreversible damage—perhaps even for catastrophe.
Given that potential, there appears to be a shift in focus from chemistry and mathematical modeling of the stratosphere to questions of economics and international politics. Coping with the threat almost certainly will be tougher than establishing it in the first place.
This article is based on material submitted by Irving Hoch, a senior fellow in RFF's Renewable Resources Division.
A version of this article appeared in print in the May 1981 issue of Resources magazine.
