To Örebro University

This study is a consequence of a distinct fishdecline in the Danube river since the beginning of the 1990s. In contrast to the decline of fish population, former studies have repeatedly documented that the water quality along the Danube river is improving. However, the conclusion of a pilot study in 2002 was that a high hazard potentialis associated with local sediments. The present study documents that sediment samples from the Danube river showed comparatively high aryl hydrocarbon receptor mediated activity in biotests, using the cell lines GPC.2D.Luc, H4IIE(DR-CALUX®) and RTL-W1. The combination of chemical analysis, fractionation techniques and different in vitro tests revealed that priority pollutants could not explain the main induction, even though the concentrations of prioritypolycyclic aromatic hydrocarbons (PAHs) were very high (maximum in the tributary Schwarzach, sum of 16 EPAPAHs 26 μg/g). In conclusion, this investigation shows that nonpriority pollutants mainly mediate the high inductionrates. Nevertheless, owing to the effects of PAHs towards fish and the connection between dioxin-like activity andcarcinogenicity, the link between contamination and the fish population decline cannot be ruled out.