Substances of very high concern under REACH - an evaluation of uncertainties in the enviromental risk assessment of endocrine active substances

The aim of the present project was to identify the most relevant factors increasing the uncertainty of the environmental risk assessment (ERA) of endocrine active substances as compared to baseline toxicants. The evaluation was supported by data on endocrine effects of six model substances on fish and aquatic invertebrates. Two key factors were identified: (1) The current evaluation of endocrine effects only covers effects on the estrogen / androgen and thyroid axis, while other endocrine modes of action and, especially, effects on invertebrates are insufficiently covered. (2) At present, it is difficult to assess whether the results of tests with few standard test species are protective for all wildlife species. For fish, effect concentrations in species with similar metabolic capacities are often in the same order of magnitude, but larger differences are observed between species that differ in their metabolic capacities. For invertebrates, cross-species extrapolation is far more complex. This is due to the much higher diversity and heterogeneity of invertebrates and the often fragmentary knowledge on endocrine effects and the underlying processes. The uncertainty of the ERA of endocrine active substances is also increased by mixture effects. It may be increased if worst case exposure conditions coincide with sensitive developmental windows. Further factors (e.g. the irreversibility of effects, effects on the reproductive behaviour, and effects with uncertain population relevance and low-dose effects) and the specificity of the identified factors for endocrine active substances are discussed.