Deriving threshold values for substances with a lower risk profile by applying TKTD models

Samenvatting

In this report the TKTD approach was applied to compounds used in crop protection that are classified as ‘limited’ risk for aquatic organisms. Most low-risk compounds are biological by nature (being either organisms or being of biological origine) and therefore not suitable for chemical based approaches. The reason is that the equilibrium a TKTD model supposes does not exist between the biological pesticides and the target pest organism. Compounds with limited risk (compounds with a H412 or H413 hazard classification) were therefore select from the EFSA pesticide database, which resulted in 14 synthetic chemical compounds. Effect thresholds could be estimated for a number of species/compound combinations. The database of two compounds included enough data to generate a Species Sensitivity Distribution (SSD). As a proof of concept an assessment based on effect thresholds is feasible and will generally lead to lower values than the standard risk assessment. Such an approach takes away most drawbacks from an LC50 or EC50 based approach and lower assessment factors may be used.