Contamination of a continental waters by organic micropollutants
There are about 50,000 to 60,000 chemical compounds used for technical purposes. Some are toxic and the discharge of these substances in the environment can be a threat to the balance of aquatic ecosystems and to human health. Several lists of dangerous substances, also called major chemical pollutants, have been drawn up by various national or international bodies such as the EPA in the United States, the EEC in Europe or the World Health Organization (WHO). The need to protect the aquatic environment and human health has also led to the establishment of standards and of quality criteria for natural and drinking water subject to these chemical contaminants. There are several sources of pollution, punctual sources such as urban and industrial effluents and diffuse sources such as run-offs from agricultural land and urban areas and atmosphere fallout. Various biogeochemical processes determine the mechanisms by which organic pollutants are transported and transformed in the aquatic environment. Bioaccumulation in living organisms represents an important aspect of their behaviour. A first assessment of the quality of continental waters (rivers, lakes and groundwater) is made by examining the data collected by the international GEMS/WATER surveillance network carried out by two United Nations Agencies, WHO and UNEP. Other sources of information, published in the literature, were also used in order to determine the level of concentration of different groups of organic pollutants found in natural waters and in drinking water. Most of the data collected come from a limited number of industrial countries : North America, Europe and Japan. There is a serious lack of informations concerning the quality of continental waters in numerous countries in Africa, South America and Asia. At present, the procedure of global chemical pollution surveillance is far from satisfactory.