The researchers studied pesticide contamination at more than 100 monitoring sites on streams flowing through predominantly agricultural lowland regions in 12 federal states in Germany
In a nationwide monitoring programme, a consortium of scientists led by the Helmholtz Centre for Environmental Research (UFZ) has shown that the governmental thresholds for pesticides are generally too high and that even these excessively high levels are still exceeded in over 80 per cent of water bodies. As they published in the scientific journal Water Research the loss of biodiversity can only be halted if the environmental risk assessment of pesticides is radically revised.
For two years, the researchers studied pesticide contamination at more than 100 monitoring sites on streams flowing through predominantly agricultural lowland regions in 12 federal states in Germany. They found significant exceedances of the RAC value- the concentration of an active ingredient specified in the official approval procedure for a pesticide, which should not be exceeded in the water body in order to prevent negative effects on aquatic organisms. In most of the small streams investigated, the RAC values were exceeded (81 per cent). In 18 per cent of the streams, such exceedances were detected for more than 10 pesticides.
The researchers were able to reveal that pesticides affect aquatic invertebrate communities at much lower concentrations than previously assumed by the pesticide risk assessment. The concentrations depend on which species are to be conserved. For example, sensitive insect species such as caddisflies and dragonflies require much lower (1.000-fold) threshold values than snails and worms.
In the course of the project, the scientists also found that the type of sampling has a drastic influence on the concentrations of pesticides measured.
