Aquatic toxicity integrated testing and assessment strategies (ITS) for difficult substances: case study with thiochemicals

Abstract Background An Integrated Testing and Assessment Strategy (ITS) for aquatic toxicity of 16 thiochemicals to be registered under REACH revealed 12 data gaps, which had filled by experimental data. These test results are now available offer the unique opportunity subject previous estimates obtained read-across (analogue category approaches) an external validation. The case study so-called difficult substances due instability poor water solubility, challenging established ITS. Results new confirm predictions acute with indicating a 2–5 times lower than previously predicted. thus conservative close results. good agreement can attributed fact that we limited extrapolations narrow chemical groups similar SH-group reactivities. further strengthen externally validate existing trends based on similarity in structures, mode action (MoA), solubility stability source target compounds media. Based data, reliable revised PNECs could derived requirements these largely fulfilled. Appropriately adapted ITS therefore able reduce vivo tests fish even replace them alternative information. Conclusions Both information such as rapidly transformed considerable uncertainty. For example, use either nominal, initial or time-weighted average concentrations contributes variability In thiochemicals, weight-of-evidence (WoE) approach determining nominal may most appropriate choice reflect environmental conditions. Overall, uncertainties historical information, here from read-across, have considered relation how much uncertainty is acceptable protection one hand certainty technically feasible other.