Micropollutants in watercourses
Micropollutants include pesticides, pharmaceuticals and other chemicals that occur in very low concentrations in watercourses. Even in these very low concentrations, they can have negative effects on aquatic organisms. They enter watercourses from wastewater treatment plants, agriculture, residential areas and traffic.
The Waters Protection Ordinance (WPO) sets ecotoxicological limit values for 19 pesticides and 3 pharmaceutical products. If these limits are exceeded, sensitive animal and plant species may be harmed.
poor
impossible to evaluate
Pesticides exceed their ecotoxicological limits in almost 60% of the watercourses analysed. In almost 8% of the streams, they exceed this limit more than 10 times a year. These contaminants occur most frequently in small and medium-sized watercourses in the intensively farmed and densely populated Swiss Plateau.
The three pharmaceutical products regulated in the WPO (azithromycin, clarithromycin, diclofenac) exceed their ecotoxicological limits in almost 40% of the watercourses investigated. In 13% of watercourses, the limit is exceeded more than 25 times a year – i.e. almost all year round. The painkiller diclofenac is responsible in the majority of cases. Medium-sized and large rivers with a high proportion of treated wastewater from wastewater treatment plants are most affected.
While pharmaceutical product often exceed limit values throughout the year, exceedances of pesticides typically occur during the period when plant protection products are applied.
As aquatic organisms can be harmed when ecotoxicological limit values are exceeded, the status is assessed as poor. Since the observation period is short, it is not yet possible to establish a trend.
Many European watercourses are also polluted with micropollutants and are in poor status.
The concentrations of pesticides and pharmaceuticals in watercourses are recorded nationally in the National Monitoring of Surface Water Quality for Micropollutants (NAWA TREND MP). This monitoring network currently comprises 38 monitoring sites and is operated by the cantons in close cooperation with the Federal Office for the Environment. The monitoring sites are located in the Swiss Plateau, Ticino, the Rhone Valley, and Jura, thus covering Swiss streams and rivers with sources of micropollutants in the catchment areas. NAWA TREND MP analyses all sizes of watercourses, from small streams to large rivers.
Evaluations are based on the annual share of monitoring sites in the NAWA TREND MP programme at which ecotoxicological limit values for the continous pollution as defined in Annex 2 No 11 para. 3 WPO are exceeded at least once in biweekly composite samples.
The results are evaluated in accordance with the intercantonal recommendation for assessing organic micropollutants in watercourses as per Annex 2 WPO (Micropollutants – Modular Stepwise Procedure).
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