Regulatory bioaccumulation assessment of nanomaterials. Development of new concepts and testing procedures

The special properties and the wide range of possible applications of nanomaterials (NMs) make them an essential part of our everyday life. The use of nanomaterials in almost all branches of industry has made nanotechnology a large and immensely growing market. The volume of NMs produced annually and used in many products is about several million tons. However, this also means that large quantities of these NMs find their way into the environ-ment. NMs can reach the environment via wastewater, where they can be ingested, enriched and passed on through the food chain by aquatic organisms.
Therefore, NMs, like other chemical industrial products, are subject to regulation and risk as-sessment including investigations on their potential to accumulate in the environment. Howev-er, the test systems and assessment schemes currently used for this purpose were not de-veloped for NMs. In addition, testing with the established method requires an enormous amount of fish and thus poses an ethical problem and a financial and logistical challenge.
In the studies of this thesis, therefore, test systems were developed which allow the determi-nation of the bioaccumulation potential of NM using invertebrates such as filtering bivalves or amphipods. For this purpose, a test system was developed which allows a constant and sta-ble exposure. In addition, studies with fish were conducted to compare the results with those obtained with invertebrates exposed to NMs in the new test system.
However, using single particle ICP-MS and adapted methods of correlative microscopy, it could be shown by the example of silver nanoparticles (AgNPs) that the accumulation of met-als after dietary and aqueous exposure can be primarily explained by the uptake of ions re-leased by the NMs. The results of the laboratory studies showed that invertebrates are not only well suited for bioaccumulation studies, they also provided a clear indication on the role of benthic invertebrates regarding the transfer of NMs in the (aquatic) food chain.
A new assessment scheme for the evaluation of the bioaccumulation potential of NMs was developed integrating the new H. azteca bioaccumulation test. Modified regulatory endpoints are suggested considering the uptake pathways of NMs and allowing a clear definition of the NMs as “bioaccumulative” or “non-bioaccumulative”. By means of the developed methods and the assessment scheme it might be possible in the future to reduce the amount of fish without impairing the quality of the regulatory risk assessment.