Pesticide Residues in Some Baltic Animals—a Review of Selected Literature

During the last few years, considerable efforts have been devoted to the tracing of halogenated hydrocarbons, particularly DDT and PCB, and of mercury in Baltic animals. These investigations have already produced some important generalizations, which may be summarized as follows: (1) The concentrations of halogenated hydrocarbons and mercury in the tissues of Baltic animals are in general higher than those found in the corresponding species on the west coast of Sweden and in the Norwegian waters. (2) The highest levels of DDT compounds seem to occur in the animals of the southern Baltic and the Sound (Oresund). (3) The highest contents of methylmercury in the Baltic fish occur in certain coastal areas, usually polluted by pulp mill wastes, while the fish caught in the open sea seem to be less contaminated. (4) Especially high concentrations of pesticide residues have been observed in fish-eating birds and mammals of the Baltic, viz, in animals representing the top levels of the food chains. (5) No fatal poisoning of fish and waterfowl due to high concentrations of pesticides has so far been observed in the Baltic area. The situation is worse with white-tailed eagles and some other raptorial birds whose populations have almost totally collapsed in many coastal regions, probably partly owing to the synergetic effects of all accumulated poisons. The ability of aquatic organisms to accumulate undesirable compounds from the water into their cells and tissues has created new problems in the use of aquatic resources. The 'black painting' of the Baltic Sea in the recent maps of FAO is particularly due to high levels of three compounds or their derivatives in the tissues of some Baltic animals. These three compounds are: DDT, a common insecticide since 1942; PCBs, a group of industrial wastes; and methylmercury, deriving mainly from mercury compounds used in agriculture, paper and chlorine alkali industries. The actual load of these compounds in the Baltic Sea is not exactly known, since all of them have an ability to disperse even via air, and their use has recently been restricted or forbidden in many countries around the Baltic. Jensen and Olsson' estimated the total use of DDT in the Baltic area to be