MT. PINATUBO'S eruption last year has added to the need for international efforts to protect Earth's ozone layer. That eruption created a mist of sulfuric acid droplets that has spread through the stratosphere. These droplets help speed up the release of ozone-destroying chlorine from chlorofluorocarbons (CFCs) already present at the same height.
As the American Geophysical Union notes in its recent report on volcanism and the atmosphere, these new findings "amplify the urgency to curb the production of CFCs." They indicate that potential ozone layer loss is more serious than even the scientists who first raised a warning had thought.
The Bush administration has responded by announcing that the United States will cease production of CFCs, halons (used in fire extinguishers), and carbon tetrachloride by the end of 1996. That's some four years earlier than the international deadline set by the Montreal Protocol on Substances That Deplete the Ozone Layer.
This will significantly cut back release of the worst chemical culprits, but it is not enough. The ban will allow exemptions to produce enough of the chemicals to meet such "essential uses" as servicing fire estinguishers, medical devices, and existing refrigeration equipment. Also, the class of chemicals that will replace CFCs as refrigerants, known as hydrochlorofluorocarbons (HCFCs), can still carry some chlorine to the stratosphere.
Meanwhile, atmospheric scientists are concerned about another ozone destroyer - chlorine's chemical cousin bromine. The wide spread use of methyl bromide as a pesticide is the main source of bromine that reaches the stratosphere. The United States is urging an international phaseout of this chemical. But some other countries are concerned about their food supplies if an equally safe substitute isn't available.
The threat to the ozone layer is turning out to be even more complicated than expected. Widely hailed international action to curb production of ozone depleting chemicals has created a false sense that the problem is being solved. It isn't. In fact, that problem needs even more international attention than it already has received.