Ecological effect assessment by species sensitivity distribution for 68 pesticides used in Japanese paddy fields

In this study, the species sensitivity distributions (SSDs) of 68 pesticides commonly used in Japanese paddy fields were analyzed based on collected acute toxicity data as a higher-tier ecological effect assessment. Then, based on each SSD, the 5% hazardous concentration (HC₅) values were calculated as the predicted no-effect concentrations for aquatic ecosystems. The differences between HC₅ and registration criteria were small (within 10-fold) for 50 of the 68 pesticides. However, there were more than 10-fold differences for 9 insecticides and 9 herbicides of specific modes of action. These results suggest that the current effect assessment scheme could underestimate the effect of such pesticides. This is caused by the mode of action specific properties of species sensitivity difference.