Does the actual standard of 0.1 μg/L overestimate or underestimate the risk of plant protection products to groundwater ecosystems?

The present groundwater standard of 0.1 μg/L for plant protection products (PPPs) has been under much debate because an ecotoxicological base is missing. In the present study, groundwater threshold values were calculated for all PPPs currently included in Annex I to Directive 91/414/EEC using three different approaches: (1) first-tier (Daphnia magna and Vibrio fisheri); (2) species sensitivity distributions, constructed for surrogate freshwater organisms for the truncated groundwater biodiversity; (3) the case-based model PERPEST. For the majority of the PPPs, the trigger value of 0.1 μg/L appears to be sufficiently protective. However, it may not fully protect groundwater life from several insecticides. Implications for the environmental risk assessment of groundwater and recommendations for future research are discussed.