Non-relevant metabolites of pesticides

A blind spot in risk assessment and how it can be eliminated

Abstract

A risk that has not been considered in the approval process for plant protection products is that the risk of a possible future reclassification of supposedly irrelevant metabolites as relevant is not taken into account and, as a result, concentrations of irrelevant metabolites are accepted that could lead to limit values being exceeded in the event of a subsequent reclassification. This poses a particular problem in water protection areas, as the only consequences are usually expensive treatment or the abandonment of the resource. In principle, this risk can only be controlled by applying the precautionary principle and prohibiting the use in water protection areas of active substances whose metabolites can occur in concentrations greater than 0.1 µg/L in raw water. This requires that the associated maximum permissible concentration of metabolites in seepage water be defined as the benchmark for approval. The article presents a suitable method for this based on a probabilistic calculation approach.