title: The legacy of pesticide pollution: An overlooked factor in current risk assessments of freshwater systems.
abstract: We revealed a history of legacy pesticides in water and sediment samples from 19 small streams across an agricultural landscape. Dominant legacy compounds included organochlorine pesticides, such as DDT and lindane, the organophosphate chlorpyrifos and triazine herbicides such as terbutylazine and simazine which have long been banned in the EU. The highest concentrations of legacy pesticides were found in streams draining catchments with a large proportion of arable farmland suggesting that they originated from past agricultural applications. The sum of toxic units (SumTUD.magna) based on storm water samples from agriculturally impacted streams was significantly higher when legacy pesticides were included compared to when they were omitted. Legacy pesticides did not significantly change the predicted toxicity of water samples to algae or fish. However, pesticide concentrations in bed sediment and suspended sediment samples exceeded safety thresholds in 50% of the samples and the average contribution of legacy pesticides to the SumTUC.riparius was >90%. Our results suggest that legacy pesticides can be highly significant contributors to the current toxic exposure of stream biota, especially macroinvertebrate communities, and that those communities were primarily exposed to legacy pesticides via the sediment. Additionally, our results suggest that neglecting legacy pesticides in the risk assessment of pesticides in streams may severely underestimate the risk of ecological effects.
authors.affiliation: Aarhus University, Department of Bioscience, Vejlsøvej 25, 8600 Silkeborg, Denmark. Electronic address: jr@bios.au.dk.
authors.forename: Jes J
authors.initials: JJ
authors.lastname: Rasmussen
authors.affiliation: Aarhus University, Department of Bioscience, Vejlsøvej 25, 8600 Silkeborg, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Wiberg-Larsen
authors.affiliation: Aarhus University, Department of Bioscience, Vejlsøvej 25, 8600 Silkeborg, Denmark.
authors.forename: Annette
authors.initials: A
authors.lastname: Baattrup-Pedersen
authors.affiliation: University of Copenhagen, Department of Plant and Environmental Sciences, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
authors.forename: Nina
authors.initials: N
authors.lastname: Cedergreen
authors.affiliation: Technical University of Denmark, Department of Environmental Engineering, Miljoevej Build. 113, 2800 Kgs. Lyngby, Denmark.
authors.forename: Ursula S
authors.initials: US
authors.lastname: McKnight
authors.affiliation: Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment, P.O. Box 7050, SE-750 07 Uppsala, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Kreuger
authors.affiliation: University of Copenhagen, Department of Biology, Freshwater Biological Laboratory, Universitetsparken 4, 2100 København Ø, Denmark.
authors.forename: Dean
authors.initials: D
authors.lastname: Jacobsen
authors.affiliation: Aarhus University, Department of Bioscience, Vejlsøvej 25, 8600 Silkeborg, Denmark.
authors.forename: Esben A
authors.initials: EA
authors.lastname: Kristensen
authors.affiliation: Aarhus University, Department of Bioscience, Vejlsøvej 25, 8600 Silkeborg, Denmark; NIVA, Section for Freshwater Biology, Gaustadalléen 21, NO-0349 Oslo, Norway.
authors.forename: Nikolai
authors.initials: N
authors.lastname: Friberg
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000032:analysis*; D010575:Pesticides / Q000032:analysis*; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000032:analysis*
chemical_list: D010575:Pesticides; D014874:Water Pollutants, Chemical
keywords: Environmental risk assessment; Legacy pesticides; Mixture toxicity; Pesticide monitoring; Streams