What is ozone?

Human, plant, and animal life on Earth is protected by a fragile shroud or layer of ozone gas, a naturally­occurring form of oxygen which is highly poisonous. At ground level, ozone contributes to smog and acid rain. But high up in the stratosphere (25­30km above the earth), ozone forms a screen against the sun's lethal ultraviolet (UV) rays. Without this layer, UV radiation would kill all life on this planet.

What's happening to the ozone layer?

There is growing scientific evidence that persistent, synthetic (man­made) chemical pollutants are rapidly destroying the ozone layer. A hole has appeared in the layer above the Antarctic and there is a general thinning of ozone around the world, allowing increasing amounts of harmful UV radiation to reach the earth's surface.

What does UV radiation do?

A small amount of UV already penetrates the ozone layer, causing human skin cancer, which kills some 12,000 people a year in the United States alone. UV also affects the immune system, our inbuilt resistance to disease. This means that it is easier for cancers to establish themselves and grow, and that we are more vulnerable to diseases such as herpes. In addition, it causes cataracts and dims eyesight. Increased radiation will make us more susceptible to all these health problems.

But UV radiation doesn't only harm humans: it debilitates all living things. It damages more than two­thirds of the world's plant species. Higher UV levels are likely to reduce crop yields, which will seriously affect food supplies. Marine life is also threatened. Especially vulnerable are the microscopic plankton that drift on the surface of the sea. These tiny organisms play a vital role in the marine food chain and absorb over half the world's carbon dioxide emissions.

How is ozone destroyed?

Many chemicals react with ozone to destroy it. They also contribute to the warming up of the climate, known as the "greenhouse effect". The black list includes nitric and nitrous oxides from vehicle exhausts, and carbon dioxide produced by burning fossil fuels such as coal. Other gases such as halons and methyl bromide (used as a pesticide) also damage the ozone layer, but the most destructive chemicals by far are a group of chlorine­containing substances called chloro­fluorocarbons (CFCs).

CFCs float upwards from the earth's surface, taking about eight years to reach the stratosphere. The intense UV radiation they encounter in the stratosphere gradually breaks them down. As the CFCs disintegrate they release chlorine, which reacts with ozone, converting it into ordinary oxygen that offers no protection against UV radiation. Meanwhile the chlorine, which acts simply as a catalyst, is not affected by its contact with the ozone and lives on to destroy thousands more ozone molecules. A single CFC­molecule can destroy 100,000 molecules of ozone.

What are CFCs?

CFCs are gases used as (i) propellants in aerosols (ii) insulating materials in refrigerators and (iii) artificial plastic foams for use as food containers, and in furniture and carpets.

When these cheap­to­produce and extremely stable chemicals were first discovered, they were greeted as miracle substances that would revolutionize modern life. Now, however, manufacturers are having to look around for alternatives.

What state is the ozone layer in today?

Every October, an ozone hole opens above Antarctica. Each year, scientists observe that this hole is getting bigger, and that its effects are becoming more obvious. In early 1992, there were reports of blindness in fish, sheep, and rabbits in southern Chile. Doctors in the area found they were treating significantly increased numbers of patients with allergies and skin and eye complaints.

The northern hemisphere's ozone layer is suffering too. The United States, most of Europe, northern China, and Japan have lost as much as 6 per cent of their protective filter. The United Nations Environment Programme (UNEP) calculates that every 1 per cent loss of ozone results in an additional 50,000 skin cancers and 100,000 cases of blindness from cataracts worldwide.

What are we doing about it?

Governments have been working to phase out CFCs. Between 1988 and 1992 the world's consumption of the lethal chemicals dropped by 40 per cent. In February 1992, the European Community and the US announced that they would phase out CFCs and other ozone depleting substances (halon, carbon tetrachloride, and methyl chloroform) by 1995.

In addition, industry should recycle CFCs so that the gases can be reused. Some electrical appliance makers are already incorporating the cost of recycling CFCs in the purchase price of their new refrigerators.

Aerosol manufacturers have introduced ozone­friendly aerosols which replace CFCs with alternative propellants. However, natural spray perfumes, hand pumps, and trigger spray products (which use no propellant of any kind) are more likely to provide an environmentally sound alternative to aerosols.

It is possible to replace CFCs by other synthetic chemicals, but it is uncertain how effective these are, and whether or not they might be equally damaging to the environment. For example, solvents like methyl chloroform, carbon tetrachloride, and methylene chloride are toxic chemicals in their own right, some of them linked to cancer. They should not, therefore, be used as CFC replacements.

New generation HCFCs (CFCs with a hydrogen atom added) are being produced. These have a much lower ozone depletion potential. However, safety tests revealed that HCFC142b, used as a foam­blowing agent and refrigerant, is flammable, while others are poisonous and cause eye deformities in mice.

HCFCs 123 and 134a (used principally as foam­blowing agents and aerosol propellants) are thought to be safe to humans, though just how effective they will be remains to be seen. For instance, HCFC134a is a less efficient refrigerating agent than conventional CFCs. A refrigerator using HCFC134a uses more electricity to maintain the same temperature, so more fossil fuel has to be consumed to produce the necessary electricity. This means that more carbon dioxide is emitted. So helping solve one problem may in fact create others.

It is important for the world to develop alternative technologies so that in the future aerosols, refrigerators, and air­conditioners can all function without using dangerous chemicals.

It is also vital that the richer countries in the industrialized world help developing countries in the South to phase out CFCs. The ozone layer, after all, protects the whole planet.

WWF aims to conserve nature and ecological processes by:

• preserving genetic, species, and ecosystem diversity
• ensuring that the use of renewable natural resources is sustainable both now and in the longer term
• promoting actions to reduce pollution and the wasteful exploitation and consumption of energy

A WWF International quarterly Publications list is available on request.

August 1993