Authors: Ferincz, Árpád; Weiperth, András;Lente, Vera;Hegedűs, Anna;Keszte, Szilvia;Kondor, Attila;Pirger, Zsolt;Molnár, Éva;Maász, Gábor;Urbányi, Béla;

High quantity of drugs and other personal health care products emitted to natural surface waters through the municipal wastewater treatment plants. The effect of this diverse mixture of compounds on the living organisms occurring these habitats is completely unknown. Our main goal was therefore to assess this potential effect on the level of fish assemblage. For this, all permanent watercourses of the Budapest (Hungary) metropolitan area were surveyed (altogether 64 sites). Fish assemblage composition and parallel environmental variables (landscape and local scale), water quality parameters and drug residuals were determined. Fish were caught at 40 sites, therefore further analyses were carried out using this filtered database. Additional filtering, regarding the drug residuals has been made: compounds with minimal (<10ng/l) concentration or frequency of occurrence (<3 sites) were excluded. Data analyses were based on ordination techniques, variable selection and variation partitioning. Significant effect of five, mostly psychoactive drug residuals were identified by the variable selection. Relative effectiveness of the different background variables was determined, which called the attention on the high potential importance of drug residuals in the fish assemblage composition of urbanized areas.