Integrative risk assessment of endocrine disruptors in Switzerland

The objective of the project was to develop an environmental fate model for various substances with endocrine-disrupting potential for the Glattal/Greifensee region in Switzerland and to assess the concentration levels. The model provides an estimate of environmental concentrations based on mass flow calculations from the source of the emissions to the final fate in the environmental compartments. Based on the chemical properties of 20 substances studied in the NRP50 program, the estimated quantities of the substances used and their respective applications, the model predicts mass flows on a local level. Taking into account the respective water flows, these mass flows result in predicted environmental concentrations in surface water and groundwater. These concentrations can be interpreted as averaged levels with geographical resolution in the local scenario. The estrogenic equivalent concentration was assessed by estrogenic equivalence factor-weighted addition of the individual substance concentrations for four different toxicological endpoints. From the 20 substances modelled in this project only a few substantially contribute to the overall endocrine disruption potential. For three of the endpoints used the steroid hormones dominate the endocrine potential. Only the application of the yeast estrogen system (YES) assay predicts a dominant endocrine potential for the degradation products of nonyl phenol-poly-ethoxylates (NPnEO) in the year 2004, which was expected to decrease significantly in the year 2007 due to new legislation (almost complete application ban of NPnEO-based detergents as of August 2006). On the basis of the model's geographical resolution it is possible to identify 'hot spots' in terms of high endocrine-disruption potential in the modelled region. For the densely populated and industrialised Glattal/Greifensee region sewage treatment plants discharging into relatively small receiving water systems show the highest endocrine disruption potential (estradiol equivalence concentration of up to 2 ng/l for the vitellogenin synthesis induction endpoint). In addition to modelling the status quo with respect to endocrine disruption possible future risk reduction measures have been assessed for one identified hot-spot. Whereas an increase in sludge retention time in the existing STP had a moderate effect on the overall endocrine potential, an additional ozonation step showed significant reduction for most endocrine-disrupting substances.