A NASA-sponsored international study last week documented a weakening of Earth's ozone shield. This raises the question of how to replace the highly useful chemicals that attack the ozone. Indeed, the efforts of the global chemical industry to find such substitutes are as important environmentally as is the 31-nation agreement to curb use of the damaging chemicals. Without substitutes, it will be hard to extend the agreement to provide the even tighter restrictions that will eventually be needed.
Happily, such efforts are under way. As the industry weekly Chemical and Engineering News noted in a recent review, ``Now that restrictions on the output of [the suspect] chemicals are inevitable, the race [to find substitutes] is on.''
But it will probably be the better part of a decade at least before such substitutes are adequately available.
Ozone is a type of oxygen with three atoms per molecule. It forms under action of sunlight 15 to 25 miles up in the stratosphere where it absorbs harmful solar ultraviolet radiation. Two main types of industrial chemicals threaten it: chlorofluorocarbons (CFCs) - used as refrigerants, for cleaning electronic parts, and as blowing agents for plastic foams - and halons (fluorocarbons that contain bromine) used for firefighting.
When these highly stable chemicals escape, instead of breaking down in the lower atmosphere they survive to migrate into the stratosphere. There they take part in complex reactions where their chlorine and bromine atoms contribute to ozone loss.
The search for substitutes involves finding CFCs that will break down in the lower atmosphere or finding different types of chemicals altogether. Some CFC substitutes are already known. ``Search'' in their case means fully testing them for effectiveness and safety. But at the moment, there are no clear substitutes for halons.
The CFC/halon curbing protocol signed in Montreal last September would freeze halon use at 1986 levels and gradually cut back use of CFCs to half their 1986 level by the end of the century. It goes into effect next January if 11 nations representing two-thirds of global use of the chemicals ratify the agreement by then. So far, Mexico has ratified it and the United States Senate last week voted 83 to 0 in favor of ratification.
These curbs will hit users of the chemicals hard if substitutes aren't available. But, as noted above, the race to find substitutes is on. For example, 13 companies in Britain, Japan, the United States, and West Germany are cooperating in the testing. American Telephone & Telegraph has developed a substitute for a CFC used for some electronic component cleaning and will make this technology available to others, to cite a second example.
This intensive search should ultimately be good for business. As economist Stephen Anderson of the US Environmental Protection Agency observed during a conference on the subject last month, ``It's a billion-dollar opportunity'' for the companies that ``come up with solutions first.''
A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.