A study by ECETOC has investigated the extrapolation of data from ecotoxicity tests carried out in water to assess toxicity in soils and sediments, using the Equilibrium Partitioning Methodology (EPM).
When assessing a chemical’s potential effects on the environment, there is often much more data available on aquatic toxicity than on the possible impact on species from other compartments such as soil and sediment. This is because lower-tier environmental safety assessments typically rely on aquatic toxicity data only. The scheme for classification and labelling for environmental hazards also uses only aquatic hazard data. Results from non-aquatic testing are therefore rather scarce.
However, current regulation requires chemical safety assessment to cover other environmental compartments, such as soils and sediments. Until now, there has been no clear consensus about the extent to which aquatic toxicity data are sufficient for managing safety in other compartments.
The ECETOC Task Force therefore compiled and analysed a database of substances for which aquatic ecotoxicity data and soil and/or sediment ecotoxicity data are simultaneously available. A large number of datapoints was used in the study. A thorough assessment of the quality of the data would have been optimal, but was not within the scope of the work.
Overall, the Task Force concluded that the dataset used limited the ability to draw concrete conclusions on the mechanistic validity of EPM. However, the findings do not contradict previous studies that demonstrate that EPM is fit for purpose to support environmental risk assessments when information on soil/sediment toxicity are limited or testing is not feasible. Known exceptions are sediments with high soot content as well as specific sediment organisms that live on top of the sediment.
Based on their work, the Task Force has made a number of suggestions for further work in this area.