New threats to the sky

ANNE STEACY September 14 1987

New threats to the sky

ANNE STEACY September 14 1987

New threats to the sky


At their Antarctic base camp on the frigid shores of the Weddell Sea,

1,500 km from the South Pole, a team of British scientists discovered an ominous phenomenon in 1977. The researchers were measuring the con centration of strato spheric ozone, and they said that the readings they received made them suspect that their instruments were mal functioning. But the ma chines were indeed working, and the re searchers eventually concluded that there is a gaping hole in the ozone layer, the gas that shields the earth from

rean published their findings in the British scientific journal Nature. He and other scientists now say that the hole over Antarctica is as big as the

the sun's harmful ultraviolet rays. The alarmed scientists continued to study the hole as it increased in size, and in 1985 survey team member Joseph Far-

continental United States—a deterioration in the earth’s protection that they say is caused mainly by the release into the atmosphere of manmade chemicals called chlorofluorocarbons (CFCs).

In an attempt to stop the deterioration, delegates from more than 40 countries are meeting in Montreal this week to sign a treaty that is designed to reduce harmful CFC emissions. Experts at Environment Canada in Ottawa say that up to one million tons of those chemicals —found in aerosol sprays, refrigerator coolants and products such as plastic fast-food containers—drift up to the stratosphere every year. There, in a layer of the atmosphere that extends nine to 22 miles above the earth, the CFC emissions encounter and destroy ozone in a series of chemical reactions. That is worrisome, scientists say, because the ozone blocks more than 90 per cent of the sun’s ultraviolet rays. A significant increase in ultraviolet radiation would have a devastating effect on plant and animal life on earth.

Delegates to the Montreal conference-sponsored by the United Nations Environment Program—say that they hope to formalize an international treaty that, in three years, will limit CFC production to 1986 levels, and then halve chemical emissions by 1994. They also plan to draft economic sanctions for use against any countries that refuse to sign the treaty. But some observers say that achieving international agreement on those issues will be difficult. For one thing, drastically reducing CFC use would cost governments and industry billions of dollars, because nonpolluting substitutes are more expensive. Still, such experts as Dr. Sherwood Rowland, a noted specialist in ozone chemistry at the University of California at Irvine, say that the health risks posed by continued CFC use are even greater. Declared Rowland: “My recommendation is a 95per-cent cut in CFC use immediately.”

Ozone itself, a three-atom form of oxygen, is a pungent, slightly bluish gas. At ground level, ozone from vehicle exhaust and gasoline vapors is a harmful air pollutant. Conversely, the nontoxic, nonflammable CFC compounds that were first discovered during the 1930s are harmless on the earth’s surface. But in the stratosphere, searing ultraviolet radiation breaks CFCs into components that include chlorine molecules—each one of which is capable of destroying as many as 100,000 ozone molecules.

That destruction will have severe consequences if it is allowed to continue unchecked, researchers say. For one thing, some experts predict that greatly increased amounts of ultraviolet ra-

diation would kill off much of the oceans’ plankton, the minute plant life that forms the basis for the aquatic food chain, and would damage the world’s major food crops. The U.S. Environmental Protection Agency has reported on another potential danger, predicting that a further reduction of as little as 2.5 per cent in stratospheric ozone could result in an additional 15,000 human skin-cancer deaths each year.

At the centre of the hole over desolate Antarctica, the ozone layer has already decreased by a staggering 40 per cent during the past 10 years. But experts stress that it is difficult to gauge the atmospheric damage caused by CFC pollution because it takes as long as five years for the chemicals to ascend to the ozone layer. Once aloft, however, CFCs cause damage for up to 100 years.

In Canada, the federal government banned the use of CFCs as propellants in such consumer items as hair sprays, antiperspirants and deodorants in 1980, effectively halving CFC emissions across the country. Similar measures took effect in other industrialized countries, including the United States and Britain, resulting in a dramatic decline in CFC use during the early 1980s. At the same time, however, many Third World countries continued to allow CFC gases in aerosol products, and that use now accounts for onethird of the CFC emissions entering the atmosphere. The chemicals are also used in new products that include foam insulation and padding, and as solvents for cleaning computer microchips. As they break down over time, they release component gases which rise into the stratosphere. According to Alex Chisholm, a Toronto-based atmospheric scientist with Environment Canada, the widening use of CFC products has sharpened the need for greater controls. Declared Chisholm, one of the delegates to the three-day conference that opens on Sept. 14: “This has got to be addressed now. If we wait another 25 years until we see the victims of skin cancer, the ozone layer will already have been immensely depleted and we will not be able to do anything about it.”

In the meantime, an international team of scientists sponsored by the U.S. National Aeronautics and Space

Administration is on a 43-day, $13million investigation for further study of the growing hole over the Antarctic. And in the process the scientists are checking possible contributing causes for the hole in the earth’s atmospheric

ozone hole (purple) over the Antarctic: chlorine and fast-food containers

protection. They already know that the ozone layer appears to become thinner on a seasonal basis—it is at its minimum from Sept. 21 to Nov. 21. Accord-

ing to one theory, increased solar activity at that time of year stimulates the production of nitrogen oxides, which, like chlorine molecules, destroy ozone molecules. Said Dr. Paul Crutzen, a scientist at the Max Planck Institute, a chemical research centre in Mainz, West Germany: “There are great disputes over what is happening over the South Pole, but the fact that there are chlorine chains running wild is not disputed.”

Some scientists also say that climatic changes may have helped to deplete the ozone layer over the Antarctic. But as they study developments and modify their theories, researchers generally agree that manmade chemicals are destroying the earth’s atmosphere. And their warning is grim: unless there are greater controls, those substances will pose an increasing danger to the health of the planet.