Pesticides include plant protection agents and biocides (see ICPR Technical Report no. 183) and are mostly artificially produced organic substances. In traditional agriculture they are used for “plant protection” against bacteria, algae, fungus (fungicides), plants (herbicides), insects (insecticides) and acarids (acaricides). They are supposed to protect crop plants against harmful organisms or to prevent damage. Apart from having the desired effects, the use of pesticides brings about risks for the environment.
Based on plant protection agents the ICPR has looked into diffuse input pathways (see ICPR Technical Report No. 240 and the below figure). Plant protection agents are mainly used in agriculture. However, they are also used outside of the agricultural sector, e.g. on sealed surfaces, in private gardens, on public municipal grassy areas, sports grounds, along roads or as weed killers along railway lines.
Impact loads due to diffuse influxes into surface waters often result from heavy rainfall, which, due to surface run-off, drainage and erosion leads to peak loads. Such peak loads frequently occur in smaller water bodies. The dilution and dispersion of substances in larger rivers leads to less extreme, but longer-lasting pollution.
So far, only individual pesticides have been detected on the longer term. Isoproturon has e.g. been measured since 1995 (further water quality data are available here).
Isoproturon (see ICPR Technical Reports no. 211 and 150) is a herbicide which is primarily used in cereal farming. During application periods, EU threshold levels for drinking water (red line) in Rhine and Moselle are frequently exceeded after heavy rainfall. On the long term and as there has been a ban on the substance in the EU since 30 June 2016, the annual average and maximum values will decrease.