CHLOROFLUOROCARBONS a threat to the ozone layer

Forest and Bird, Volume 19, Issue 3, 1 August 1988, Page 4

CHLOROFLUOROCARBONS a threat to the ozone layer

by

Tom Clarkson

I: New Zealand we face many threats to our environment. Nevertheless, with most of these we can approach the future with some optimism because the decisions on remedies or controls can be made entirely within New Zealand. With the right public perceptions and the appropriate political will, people, industries or the government can exert positive management over our environment at risk. However, the two greatest environmental hazards faced by New Zealand through the next few decades are almost independent of any decisions made in New Zealand. When an issue is a global one, New Zealand, with less than a thousandth of the world population, has a very small voice.* The two great hazards are the greenhouse effect, warming our atmosphere and oceans, and the depletion of the ozone layer, changing our solar radiation climate. Both these effects are caused by the unregulated release of trace gases into the atmosphere. The greenhouse effect arises largely from carbon dioxide from fossil fuel burning, and the ozone depletion from the release of an entirely synthetic group of chemicals, the chlorofluorocarbons (CFCs). In this article I will discuss only the ozone depletion problem, bearing in mind that the greenhouse effect is closely related. Earth’s radiation shield The ozone layer is the earth's radiation shield. The minute traces of this gas, between 75 and 50 kms up in the stratosphere, absorb solar ultraviolet radiation

and so protect all life below from harmful effects. A decrease in ozone concentration and a consequent increase in uv radiation leads to increased incidence of some forms of skin cancer and eye cataracts. Other parts of the biosphere are also very vulnerable to

changes in their uv climate. For example, micro-organisms in the surface layers of the sea can be seriously affected, and their niche at the bottom of the food-chain and the wide variety of juvenile species involved, means that the marine eco-system is likely to change. The ozone layer, in absorbing solar energy, also leads to the existence of the deep stable stratosphere, where vertical winds are restricted, and which is an effective cap on the weather systems below. Changes in ozone will lead to changes in weather patterns. The ozone layer is fragile. If it were all brought down to ground level the layer would only be 3mm thick. Thus it is with alarm we note that since about 1970, between 1.7 and 3 percent of stratospheric ozone has vanished from the temperate regions of the globe. This is after allowances have been made for natural variations due to the sunspot cycle, major volcanic eruptions, atmospheric circulation effects such as El Nifio, all of which influence ozone. A 1 percent depletion of ozone is estimated to lead to a 5 percent increase in skin cancer incidence. It is also very alarming that during the 1980s, ozone over the Antarctic has been vanishing for about two months each spring. This is the ‘‘ozone hole’’, where in October 1987 only about half the normal amount of ozone was present south of the Antarctic Circle. Top Chlorine has now become firmly established as the top suspect for causing the ozone hole, largely as the result of intense experimental programmes conducted by US agencies during the past two spring seasons. The chlorine is from the now ubiquitous CFC gases, which together with the

special meteorological conditions in polar regions, can rapidly destroy ozone. Chlorine from CFCs is also blamed for ozone depletion over the rest of the world. Proof is less definite, but the measured decreases are consistent with the theoretical modelling. From the time of their invention 50 years ago up until the mid- 1970s, CFCs were the ideal chemical for many industrial and consumer applications. They are inert, nontoxic and cheap and they have become almost indispensable for refrigeration, foam blowing, aerosol propellants, fire extinguishers and as solvents. In 1974, a problem was recognised. These CFC molecules are so inert that they can drift up unchanged to the stratosphere, where they are decomposed by the strong ultraviolet light, releasing free chlorine atoms. The common 2-atom oxygen molecules are broken up by ultraviolet to form 3-atom ozone. Later this reaction may reverse, setting up the natural cycle and balance of creation and destruction of ozone. A single chlorine atom from a CFC can break in to initiate an ozone-destroying reaction sequence and while remaining unchanged itself, it catalyses the destruction. The single chlorine atom can take part in

this reaction sequence perhaps 100,000 times before it is finally removed by something else. So a mere 100 grams of CFC, the amount in a single spray can, will eventually destroy over three tonnes of ozone (although some will recover through the natural creation processes). World usage of CFCs reached a peak in the mid-1970s and declined for a few years after that, due to bans on aerosol cans with CFCs in USA and some other countries. However, new uses, especially in the foam plastic industry, have led to new production records and we now produce about one million tonnes of CFCs annually. This increases the amount of CFC in the atmosphere by about 5 percent annually, and we must bear in mind that most of this will not drift sufficiently high in the stratosphere to begin its decomposition for several decades or a century.

Montreal Protocol New Zealand has signed and ratified the Vienna Convention on the Protection of the Ozone Layer (1985) which is a United Nations treaty in which nations agree not to destroy the ozone layer. Unfortunately this convention has no teeth, so during 1987 the United Nations Environment Program (UNEP) convened a series of meetings to determine an enforceable international agreement to reduce the use of CFCs. The result was the Montreal Protocol on Substances which Deplete the Ozone Layer. This specifies a phased 50 percent cutback on CFC use by 1999. The Protocol will come into force when nations representing 66 percent of world consumption have ratified. This is expected to be during 1989, when both USA and the European Community have ratified. New Zealand ratified the Protocol in June 1988. The Protocol is the compromise necessary to have any type of agreement between demands such as a 90 percent cutback by 1996 (USA) and a mere freeze of production capacity (which would allow increases for maybe a decade) (Europe). The achievement of a Protocol which included these nations as well as Japan and USSR was a major triumph for UNEP and sets a prece-

dent for other global environmental issues. Nevertheless it is clear that the Protocol itself is not strong enough to protect the ozone layer. As it stands, instead of accumulating an extra 5 percent of CFCs each year, we will accumulate only about an extra 2 percent. Even an immediate 85 percent cut back would still maintain the chlorine at present levels. However, there is hope. The prospect of a 50 percent drop in production during the next ten years is devastating for large industries and their investors. The Protocol gives such a strong signal to industry that work towards alternative technologies and voluntary cutbacks is already going ahead and it seems likely that major industries will have abandoned the dying technology well before 1999. There are also likely to be calls for a stronger Protocol at the first review of the conditions in 1990, mainly because of

the new scientific evidence of the CFCozone link that has been established since the signing in 1987. New Zealand consumes about one quarter of a percent of the world’s CFCs. The Protocol calculates the amounts of the different CFCs by their ‘‘ozone depleting potential’’, a figure derived from their chemistry. Allowing for this, usage in New Zealand in 1986 was approximately 31 percent aerosols; 27 percent plastic foams; 20 percent refrigerants; 20 percent fire extinguishers; 3 percent solvents. Consumers’ role There is very little opportunity for a domestic consumer to reduce CFC use by wise buying. About 70 percent of aerosol cans are now propelled by hydrocarbons (and the can is labelled with the propellant). In May 1988 the Aerosol Association, representing the spray can industry in New Zealand, announced its intention to completely phase out the use of CFCs by the end of 1989, well ahead of any requirement in terms of the Protocol. Some of the uses of foam plastics are trivial packaging uses and could be avoided, but the difficulty is identifying CFC-containing products which usually look much the same as plastic foams blown with hydrocarbons or other inoffensive gases. Domestic fire extinguishers, for example the 1 kg BCF type, are extremely efficient and convenient, but this compound has a very high ozone depleting potential and will eventually all escape into the atmosphere. Can we go back to dry powder extinguishers? Alternatives to the use of BCF (or halons) in commercial size fire systems do not seem to be available. However huge cutbacks in use can be made by rationalising maintenance and testing procedures. The real pressure must come on the Government, preferably with the support of responsible industry groups, to keep up the momentum of the Montreal Protocc! internationally. This can be done by New Zealand establishing a policy stronger than the Protocol. The present policy established for the Protocol negotiations is about equal in strength to the present protocol. To propose a complete phase out earlier than about 1995 would probably be too tough on our industry which must depend on the new technologies gradually coming in from overseas, but a policy aiming for a phase out about 1995 would be in line with what is probably going to be demanded from the governments of United States, Sweden, Norway, Finland and Canada. A reduction in the atmospheric concentration of CFCs will have another benefit through reducing the greenhouse effect. CFCs are particularly efficient greenhouse gases, and three of our 100 gram spray cans have an effect equal to one tonne of carbon dioxide! And that’s another story. eo Tom Clarkson is an atmospheric chemist for the New Zealand Meteorological Service. He was head of New Zealand delegations at international negotiations leading up to the Montreal Protocol in 1987. * Nevertheless, as our stand on the nuclear issue has shown, we can espouse a strong moral message for the rest of the world to note-Editor.