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According to the European Water Framework Directive, member states are obliged to ensure that all surface water bodies achieve at least good ecological status and to identify major anthropogenic stressors. Non-point source contamination of agricultural pesticides is widely acknowledged as one of the most important anthropogenic stressors in stream ecosystems. We surveyed the occurrence of 31 pesticides and evaluated their potential toxicity for benthic macroinvertebrates using Toxic Units (TU) in 14 Danish 1st-and 2nd-order streams in bed sediments and stream water during storm flow and base flow. Total pesticide concentrations and toxic potential were highest during storm flow events with maximum TU ranging from −6.63 to −1.72. We found that minimum buffer strip width in the near upstream area was the most important parameter governing TU. Furthermore, adding a function for minimum buffer strip …