The ozone layer absorbs most of the ultraviolet radiation coming from the sun and is very important for the survival of life on earth. Ozone is a gas composed of molecules of three oxygen atoms (O3). There is a layer of ozone in the stratosphere, which is most dense between 20 and 25 km above the earth’s surface.
In 1984 scientists discovered there was a hole in the ozone layer above Antarctica. The hole appears each spring and is repaired when air containing normal levels of ozone is blown in. As it is being repaired at the end of spring the ozone hole drifts over Australia, allowing increased levels of ultraviolet radiation through. It is estimated by scientists that a one per cent decrease in ozone levels produces between one and two percent increase in ultraviolet radiation. The Melbourne Bureau of Meteorology has found that there has been an 8% increase in ultraviolet radiation during the summer since 1980.
Ozone depletion allows more ultraviolet radiation through to the earth. Ultraviolet radiation can damage humans, plants and animals. It can interfere with photosynthesis in plants and cause eye problems and skin cancer in humans and animals. Skin cancer is already a disease of epidemic proportions in Australia, which now affects two thirds of all Australians. Skin cancer is a worse problem in Australia than in other parts of the world because many Australians have fair skins and yet Australia is so close to the tropics. Skin cancer is about 10 times more common amongst Australians than it is amongst other fair skinned people in Northern Europe.
Australia also has the highest incidence of the most lethal form of skin cancer, melanoma, in the world. Seven thousand Australians got a melanoma in 1991. Melanomas are increasing by at least 10% every year, which means that it is fast becoming a common cancer in Australia. It is a very aggressive cancer and quickly grows inwards and causes secondary tumours to grow on the internal organs. It is highly dangerous and life endangering.
It is estimated that about 1 in 60 Australians will get melanoma in this country. Approximately one in seven people who get melanoma cancer die from it. Although the incidence is rising the mortality rate is now falling largely due to the widespread education programme that has led people to seek medical advice early in the course of the disease. There is now a constant stream of people presenting to their local doctors with suspicious lesions.
Squamous cell carcinomas are a more common type of skin cancer that has a mortality rate in humans of about two to three per cent. This is more significant than it may seem because it is so common. About 250 Australians die each year from squamous cell carcinomas. As ozone depletion increases the incidence of skin cancer will also increase unless people reduce their exposure accordingly. It is estimated by scientists that for every one per cent decrease in ozone, there could be a 4-6% increase in skin cancers. At the moment Queens land is the most susceptible state because it is the closest to the equator and the amount of
ultraviolet radiation is stronger there.
However the ozone hole comes up from Antarctica so it affects cities that are further south such as Hobart, Melbourne and Sydney in that order. Many scientists warn that the whole problem is going to accelerate in Australia. The prediction now is that by the year 2005 there will be something like a 15% increase in the ultraviolet radiation. This could all add up to something like a 50-60% increase in non-melanoma skin cancers in Australia in the next fifteen years.
Such predictions are difficult because the relationship between ultraviolet radiation and skin cancer is complicated, especially with respect to melanomas. Moreover, such predictions assume that people will not change their habits and be more careful about being exposed to the sun. The impacts on animals and plants are even more difficult and could be far more serious because plants, and fish and plankton in particular, cannot easily move out of the sun or adopt extra protection. Yet the health of ecosystems and human beings is dependent on them.