Plant protection product residues in drinking water

Plant protection products are mostly applied outdoors and, therefore, are also released into the environment. Some of their residues or degradation products may also end up in groundwater, surface water and drinking water.

To ensure that there is no risk to consumers, a general, substance-independent limit of 0.1 micrograms per litre of drinking water applies in the EU for residues of active plant protection product ingredients and their relevant degradation products (metabolites) in groundwater and drinking water (German Drinking Water Ordinance (TrinkwV), 2001). In Germany, compliance with this limit is monitored by the federal states (Länder).

As part of applications for the approval of plant protection product active substances or for authorisation of plant protection products, the Federal Environment Agency (UBA) determines which metabolites are to be expected in which concentrations under the most unfavourable application conditions. This information is given to the BfR, which then examines in a step-by-step procedure whether these metabolites are possibly harmful to health and up to which concentration resulting health risks can be definitely excluded. The manufacturer’s application can only be granted if either the metabolites do not pose any health risks or the maximum predicted concentrations are so low that no health risks will arise from the toxicological properties of the metabolites.

Since there is no comprehensive data on metabolites from tests on laboratory animals, in case of doubt, a “worst case” approach is used to assess them based on the active ingredient studies. Furthermore, modern computer-based, “in silico” methods such as (Q)SAR analyses are playing an increasingly important role here. This involves the evaluation of (quantitative) structure-activity relationships.