The ultimate destination of most atmospheric pollutants is unquestionably the marine environment. Scores of studies have already been devoted to examining the transport, distribution, flows and impact of important groups of compounds such as polychlorinated biphenyls, polyaromatic hydrocarbons and heavy metals. Much less is know about the fate of the more volatile compounds such as benzene, toluene, xylenes, ethylbenzene (monoaromatic hydrocarbons) and volatile organochlorinated compounds such as tri- and tetrachloroethene, di- and trichloroethane, tetrachloromethane and trichloromethane. Nevertheless, these compounds - which form the target group of this project - are major atmospheric contaminants, and they belong to the group of compounds which various international authorities have said require priority action (Ministerial Declaration of the Third North Sea Conference, 1990; GESAMP, 1989; UNESCO, 1989). A number of questions must be addressed when examining the fate of atmospheric pollutants in the marine environment. Firstly, the current concentrations and the distribution of the target group must be determined, taking a number of parameters (season, temperature, distance to the coast) into account. Secondly, questions can be posed about the flows of these compounds. Lastly, questions can be posed concerning the possible effects on organisms. These considerations generate the following objectives: (1) Determination of the concentration levels of the target group (benzene, toluene, ethylbenzene, xylenes, tri- and tetrachloroethylene, di- and trichloroethane, tri- and tetrachloromethane) in the various compartments (air, water, sediment and biota) of the North Sea environment. (2) Modelling of the flows of the target group to get a better understanding of the transport processes in the North Sea environment. (3) Study of the mechanisms of biomagnification and bioaccumulation of the target group, through in vitro experiments and fugacity models.