Atmospheric ozone forms an ozone layer in the stratosphere that plays an important ecological role by filtering out most biologically harmful solar ultraviolet radiation (UV-B). Whilst only a one percent reduction of stratospheric ozone increases UV-B radiation at the Earth's surface by 2%, our activities have cumulatively reduced ozone by more than 14% between 1969/70 and 1993 over continental parts of the northern middle latitudes, and have led to the appearance of holes up to "continental size" over the poles. The harmful consequences of reduced ozone on biological life have already been established, yet further research and monitoring are needed to accurately assess the damage already done, now, and in the future, in order to respond most effectively.
This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities. Agenda 21 recommends evaluation of the effects of ultraviolet radiation on plants and animals caused by the depletion of the stratospheric ozone layer.
The harmful consequences of reduced ozone on organisms include: an estimated 2 to 4% increase in generic biological effects with a reduction of 1% in total ozone; an estimated a 4 to 6% increase in certain kinds of skin cancer with a 1% decrease in the ozone layer; impairing the effectiveness of the body's immune system; contributing to eye damage, skin infections; adversely affecting crop plants and forest species since UV-B has been shown to slow growth, interfere with germination, damage plant hormones and chlorophyll, reducing biomass; and threaten many aquatic organisms such as single-celled algae which are at the beginning of the aquatic food chain. One experiment show that all anchovy larvae are killed to a depth of 10 meters by 15 days' exposure to UV-B at an intensity 20% higher than normal.
Despite significant progress in bringing the problem of ozone-layer depletion under control, a number of outstanding challenges remain. Past (and continuing) emissions of ODS will result in increases in UV-B radiation that are likely to lead to increases in the incidence and severity of a variety of short- and long-term human health effects, particularly on the eyes, the immune system and the skin. Recent evaluations of UV-related excess skin cancer risks in Europe caused by ozone depletion suggest that, even though stratospheric ozone concentrations should reach a minimum around the year 2000 (which assumes that the measures in force are fully implemented), excess skin cancer incidence is not expected to begin to fall until about 2060, because of the time lags involved.
1. The essential characteristic about ozone in the atmosphere is that it absorbs ultraviolet radiation, especially ultraviolet B, which damages the genetic heritage of a number of life forms, including humans. A relatively small increase of ultraviolet radiation can cause, at least, reddening of the skin (sunburn) but also more seriously skin cancer and other forms of skin disease.
