Contamination by persistent chemicals in food chain and human health.

Persistent polluting chemicals are, by definition, substances which have long half-lives or disappearance rates in the environment, mainly due to their chemical stability, but often also caused by unfavourable conditions for environmental/biological mineralisation processes to take place. DDT, lindane, dieldrin, HCB, and PCB are well known examples of chemicals which can be found in various parts/compartments of the environment, and in living organisms including man. The early findings in 1950s and 1960s of the persistent chlorinated pesticides in birds and fish populations in North America and Europe were obviously the results of deliberate and extensive use of these chemicals in agriculture and industry. The findings were confirmed and substantiated by national and international monitoring programmes, and it became clear that many field observations of threatened species convincingly could be correlated to the increasing levels of contamination. Still more man-made chemicals have been drawn into the field of interests as widespread pollutants, and the geographical areas in which contamination takes place have become ever larger. The threat to groundwater resources from infiltration of pesticides into soils, and the alarming reports on contamination of mothers milk are to-day well-known examples. They are described from many parts of the world. Similarly, the food chain biomagnification of several pesticides and of PCB which were already described from Great Lakes region in North America in the 1960s and from the Baltic Sea area in Europe in the 1970s has since then been followed by identical observations in the Danube basin in Eastern Europe and in Indian provinces during the 1980s. Scientifically, we are to-day able to describe many of the fundamental processes, including environmental transport and transformation, as well as exposure, uptake and metabolic patterns for many of the persistent man-made chemicals. Accordingly, we are reasonably well informed of the most obvious cause-effect chains which govern the process of increasing pollution. We understand and can often for most of the chemicals predict the hazards of the environment as well as to man. In spite of this experience, and contrary to belief created by our scientific knowledge, the problem of contamination is still increasing. This includes the frequency of reported accidents and damages from all over the world. It is obvious, therefore, that the question becomes a matter of concern for the global society and a call for world-wide attention through international bodies develops into a matter of urgency.