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 nonylphenol-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

Removal of oxide nanoparticles in a model waste water treatment plant : influence of agglomeration and surfactants on clearing efficiency

The rapidly increasing production of engineered nanoparticles has created a demand for particle removal from industrial and communal wastewater streams. Efficient removal is particularly important in view of increasing long-term persistence and evidence for considerable ecotoxicity of specific nanoparticles. The present work investigates the use of a model wastewater treatment plant for removal of oxide nanoparticles. While a majority of the nanoparticles could be captured through adhesion to clearing sludge, a significant fraction of the engineered nanoparticles escaped the wastewater plant’s clearing system, and up to 6 wt % of the model compound cerium oxide was found in the exit stream of the model plant. Our study demonstrates a significant influence of surface charge and the addition of dispersion stabilizing surfactants as routinely used in the preparation of nanoparticle derived products. A detailed investigation on the agglomeration of oxide nanoparticles in wastewater streams revealed a high stabilization of the particles against clearance (adsorption on the bacteria from the sludge). This unexpected finding suggests a need to investigate nanoparticle clearance in more detail and demonstrates the complex interactions between dissolved species and the nanoparticles within the continuously changing environment of the clearing sludge