title: How TK-TD and population models for aquatic macrophytes could support the risk assessment for plant protection products.
abstract: This case study of the Society of Environmental Toxicology and Chemistry (SETAC) workshop MODELINK demonstrates the potential use of mechanistic effects models for macrophytes to extrapolate from effects of a plant protection product observed in laboratory tests to effects resulting from dynamic exposure on macrophyte populations in edge-of-field water bodies. A standard European Union (EU) risk assessment for an example herbicide based on macrophyte laboratory tests indicated risks for several exposure scenarios. Three of these scenarios are further analyzed using effect models for 2 aquatic macrophytes, the free-floating standard test species Lemna sp., and the sediment-rooted submerged additional standard test species Myriophyllum spicatum. Both models include a toxicokinetic (TK) part, describing uptake and elimination of the toxicant, a toxicodynamic (TD) part, describing the internal concentration-response function for growth inhibition, and a description of biomass growth as a function of environmental factors to allow simulating seasonal dynamics. The TK-TD models are calibrated and tested using laboratory tests, whereas the growth models were assumed to be fit for purpose based on comparisons of predictions with typical growth patterns observed in the field. For the risk assessment, biomass dynamics are predicted for the control situation and for several exposure levels. Based on specific protection goals for macrophytes, preliminary example decision criteria are suggested for evaluating the model outputs. The models refined the risk indicated by lower tier testing for 2 exposure scenarios, while confirming the risk associated for the third. Uncertainties related to the experimental and the modeling approaches and their application in the risk assessment are discussed. Based on this case study and the assumption that the models prove suitable for risk assessment once fully evaluated, we recommend that 1) ecological scenarios be developed that are also linked to the exposure scenarios, and 2) quantitative protection goals be set to facilitate the interpretation of model results for risk assessment.
authors.affiliation: Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Schmallenberg, Germany.
authors.forename: Udo
authors.initials: U
authors.lastname: Hommen
authors.affiliation: Bayer CropScience AG, Monheim am Rhein, Germany.|Bayer Pharma AG, Global Drug Discovery-Clinical Sciences, Wuppertal, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Schmitt
authors.affiliation: Institute for Environmental Research, RWTH Aachen University, Aachen, Germany.|Bayer CropScience AG, Monheim am Rhein, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Heine
authors.affiliation: Alterra, Team Environmental Risk Assessment, Wageningen, University and Research Centre, Wageningen, the Netherlands.
authors.forename: Theo Cm
authors.initials: TC
authors.lastname: Brock
authors.affiliation: Umweltbundesamt (Federal Environment Agency), FG IV-1.3, Section "Plant Protection Products,", Dessau, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Duquesne
authors.affiliation: Cheminova A/S, European Regulatory Office, Harrogate, United Kingdom.|Monsanto Company, St Louis, Missouri, USA.
authors.forename: Phil
authors.initials: P
authors.lastname: Manson
authors.affiliation: Dow AgroSciences, European Development Centre, Abingdon, United Kingdom.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Meregalli
authors.affiliation: DuPont Crop Protection, Stine-Haskell Research Center, Newark, Delaware, USA.
authors.forename: Hugo
authors.initials: H
authors.lastname: Ochoa-Acuña
authors.affiliation: Ctgb, Wageningen, the Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: van Vliet
authors.affiliation: Alterra, Team Environmental Risk Assessment, Wageningen, University and Research Centre, Wageningen, the Netherlands.
authors.forename: Gertie
authors.initials: G
authors.lastname: Arts
mesh_terms: D018533:Biomass; D054750:Ecotoxicology; D004784:Environmental Monitoring / Q000379:methods*; D006540:Herbicides / Q000032:analysis / Q000633:toxicity*; D019684:Magnoliopsida / Q000187:drug effects*; D008954:Models, Biological; D018517:Plant Roots / Q000187:drug effects; D018570:Risk Assessment / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical
keywords: Dynamic exposure; Macrophytes; Mechanistic effect models; Pesticide risk assessment