Hazards of pesticides to bees - 12 th International Symposium of the ICP-PR Bee Protection Group, Ghent (Belgium), September 15-17, 2014 Julius-Kühn-Archiv, 450, 2015 51 1.7 The advantage of a toxicokinetic model of the honey bee colony in the context of the risk assessment of plant protection products Kerstin Hörig 1 , Christian Maus 2 , Alexander Nikolakis 2 , Hans-Toni Ratte 3 , Martina Roß- Nickoll 1 , Walter Schmitt 4 , Thomas G. Preuss 1,2 1 Institute for Environmental Research, RWTH Aachen University, Aachen, Germany 2 Bayer CropScience AG, Monheim am Rhein, Germany 3 gaiac - Research Institute for Ecosystem Analysis and Assessment, Aachen, Germany 4 Bayer Healthcare AG, Wuppertal, Germany Corresponding author: Kerstin Hörig, kerstin.hoerig@bio5.rwth-aachen.de, Phone +49 (0) 241 / 80-23693 Institute for Environmental Research, Worringerweg 1, 52074 Aachen, Germany Abstract Within the current discussions about risk assessment of plant protection products regarding honey bees, one of the most important aspects is how to link pesticide exposure on field and landscape scale to potential effects within the colony. A dynamic toxicokinetic model may help to improve the evaluation of dose rates individuals are exposed to through various compartments of the colony, which may result from the application of plant protection products in the field. In addition, it may help to interpret the significance of ecotoxicological test results, especially from lower-tier studies, in the risk assessment and help to refine the exposure assessment and risk evaluation. Linking it to a realistic population model and a landscape-based foraging model would give an improved insight into the dynamics in a honey bee colony under exposure of plant protection products Keywords: Modelling, Toxicokinetics, Risk Assessment, Exposure 1. Introduction 1.1 Regulatory background In 2012 the European Food Safety Authority (EFSA) published a scientific opinion on the science behind the development of a risk assessment of PPPs on bees (Apis mellifera, Bombus spp. and solitary bees) as an answer to a request from the European Commission. 1 In this paper, the importance of the linkage of exposure and effects is stressed. In 2013 this scientific opinion was followed by a Draft Guidance on the risk assessment of PPPs on bees in order to “provide guidance for notifiers and authorities in the context of the review of PPPs and their active substances under Regulation (EC) 1107/2009”. 2 This draft guidance document demands several tests to determine the effects of PPPs on honey bees, bumble bees, and solitary bees of which only a part are conductible with a validated test guideline, e.g. by OECD. 3,4 For many of the proposed risk assessment procedures, a key issue is the determination of the exposure of bees to PPPs on colony level. A modelling approach may help to close knowledge gaps in this context and to support the risk assessment with scientifically robust information on exposure, which may otherwise be very complex to determine experimentally. 1.2 Modelling in the regulatory context Models may be used as valuable tools to address ecological and ecotoxicological questions that may be raised in the risk assessment of PPPs. 5 One reason for the use of models in the risk assessment of PPPs is the reduction of animals that shall be used in tests. The Regulation (EC) No 1107/2009 stresses the promotion of non-animal test methods and alternative risk assessment approaches. 6 Furthermore, a model may help extrapolating from laboratory to field conditions under consideration of landscape effects. A particularly important potential use of models in risk assessment of PPPs may be the refinement of the exposure assessment. 5