IMPACTS OF INCREASED LEVELS OF UV-B RADIATION

With the depletion of the ozone layer comes greater dangers to life on Earth. The scientific 'rule of thumb' has been that every 1% ozone depletion results in 2% increase in the amount of harmful UV-B radiation that reaches the surface of the earth. This linear relationship seems to be correct up to about 15% ozone loss. However, recent studies indicate that the ratio between ozone loss and increases in UV-B radiation becomes exponential at higher levels of ozone depletion. Thus, for example, 5% ozone loss corresponds to a10% increase in UV-B radiation but 30% and 50% ozone losses result in up to100% and 350% increases in UV-B radiation, respectively. In light of the high levels of ozone depletion observed over the Northern and Southern Hemispheres during the past five years, such non-linearities have major consequences for the biosphere and human health.

Higher levels of UV-B radiation increase the risk of severe damage to human health, e.g. eye diseases, skin cancer, immune system suppression. Increased dosages of UV-B also endanger crops, forests, plants, marine life and wildlife.

Highlights from the 1994 UNEP Assessment of the Environmental Effects of Ozone Depletion include:

Skin cancer rate on the rise: Between 1979 and 1993, the incidence of non-melanoma, the most common form of skin cancer, is already believed to have risen an average of 10% in the Northern Hemisphere, between the latitudes 55 0N and 35 0N. Even bigger increases are believed to have occurred in the Southern Hemisphere. UNEP forecasts that a sustained 1% decrease in stratospheric ozone will result in a 2% increase of this type of skin cancer.

Immune system at risk: Exposure to UV-B is now known to lower the effectiveness of the immune system. There is mounting evidence that UV-B has the ability to activate latent viruses such as papillomaviruses, herpes, and perhaps HIV. UNEP suggests that UV-B exposure might adversely influence immunity to infectious diseases, such as leishmaniasis, malaria, trichinosis, Lyme disease and fungal infections.

Sun screen ineffective: There is further evidence that sunscreens are not effective in preventing suppression of the immune system on exposure to UV-B radiation.

Fish stock at risk: 16% ozone depletion could result in 5% loss in phytoplankton (the basis of all food in the seas), which would lead to a loss of about 7 million tons of fish per year - about 7% of fishery yield.

Animals suffer: UV-B is implicated in the formation of skin cancer for several animals, especially commercially important ones such as cows, goats, sheep and also cats and dogs.

Damage to plants: UV-B radiation can alter plant form, damage tree and plant growth, change the time of flowering, make plants more vulnerable to disease and cause them to produce toxic substances. There may well be losses of biodiversity and plant species, but our ignorance of the effects of UV-B on ecosystems as a whole is far too great to allow figures to be put on these losses.