Journal Pre-proof Heavy rainfall provokes anticoagulant rodenticides’ release from baited sewer systems and outdoor surfaces into receiving streams Julia Regnery1,*, Robert S. Schulz1, Pia Parrhysius1, Julia Bachtin1, Marvin Brinke1, Sabine Schäfer1, Georg Reifferscheid1, Anton Friesen2 1 Department of Biochemistry, Ecotoxicology, Federal Institute of Hydrology, 56068 Koblenz, Germany 2 Section IV 1.2 Biocides, German Environment Agency, 06813 Dessau-Rosslau, Germany *Corresponding author. Email:
[email protected] (J. Regnery); phone: +49 261 1306 5987 Journal Pre-proof A manuscript prepared for possible publication in: Science of the Total Environment May 2020 1 Journal Pre-proof Abstract Prevalent findings of anticoagulant rodenticide (AR) residues in liver tissue of freshwater fish recently emphasized the existence of aquatic exposure pathways. Thus, a comprehensive wastewater treatment plant and surface water monitoring campaign was conducted at two urban catchments in Germany in 2018 and 2019 to investigate potential emission sources of ARs into the aquatic environment. Over several months, the occurrence and fate of all eight ARs authorized in the European Union as well as two pharmaceutical anticoagulants was monitored in a variety of aqueous, solid, and biological environmental matrices during and after widespread sewer baiting with AR-containing bait. As a result, sewer baiting in combined sewer systems, besides outdoor rodent control at the surface, was identified as a substantial contributor of these biocidal active ingredients in the aquatic environment. In conjunction with heavy or prolonged precipitation during bait application in combined sewer systems, a direct link between sewer baiting and AR residues in wastewater treatment plant influent, effluent, and the liver of freshwater fish was established.