Ecotoxicity Effect Indicator for use in the OMNIITOX Base Model

The ecotoxicity effect indicator (EFI) is used together with the input results from the fate modelling when calculating characterisation factors for ecotoxicity within life-cycle impact assessment (LCIA). A number of methods have been proposed and used in recent years involving different approaches for the estimation of the EFI. However none of these methods are found to be adequately robust and/or able to work on the low data input defined by the OMNIITOX Base Model (BM), i.e. a minimum of three acute EC50 values. Given the fact that the BM should be applicable to a significant number of chemicals, this requirement follows from the current and the most likely future data availability as defined by the proposed EU chemicals policy REACH. In this paper, a theoretical elaboration of effect-based average approaches (arithmetic mean, geometric mean and median) and the non-effect based approach (PNEC) is made focusing on their statistical robustness. Considerations about the possibility to relate the effect indicator to damage on the endpoint, the ecosystem, are also included. The effect-based approaches are tested for their robustness in estimating an HC50 in a practical test on datasets from eleven different substances representing seven different toxic modes of action (TMoA). On the basis of the theoretical elaboration and the practical tests it is recommended for the EFI to use the GM-trophic calculated as the geometric mean of three EC50 values, one from each of the three trophic levels, primary producers, primary consumers and secondary consumers comprising three different taxa, i.e. algae, crustacean (invertebrates) and fish. If more than three useable EC50 are available then the geometric means within each trophic level are used as input data to the final calculation.