www.ikts.fraunhofer.de © Fraunhofer IKTS HOW TO INVESTIGATE ADDITIVE-RELATED EFFECTS FROM MICROPLASTICS? Annegret Potthoff1, Axel Müller-Köhn1, Anita Jemec Kokalj2, Dana Kühnel3 1Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Dresden, Germany; 2University of Ljubljana, Ljubljana, Slovenia; 3Helmholtz-Center for Environmental Research GmbH – UFZ, Leipzig, Germany Contact: Annegret Potthoff | Fraunhofer Institute for Ceramic Technologies and System IKTS | Department Materials and Process Characterization | Group Powder and Suspension Characterization | Winterbergstrasse 28, 01277 Dresden, Germany | Phone +49 351 2553-7700 | annegret.potthoff@ikts.fraunhofer.de INTRODUCTION When assessing potentially harmful ecotoxicological or toxicological effects of microplastics, researchers are in a quandary:  To suit the requirements of interpretable experimental data, they wish well characterized small particles, ideally with a narrow particle size distribution and ideally doped with a well detectable element like Europium. The wished polymer particles should not contain any other substances.  To obtain results that represent real exposure scenarios, the characteristics of the test material are completely different: Microplastics found in the environment, differ in sizes and shapes – and they do not only contain the polymer itself, but an unknown quantity of unidentified chemicals. An approach that combines both, well-known characteristics and environmentally relevant properties, should be developed. The sample preparation procedure should work not only for a variety of polymers and chemicals, but also for different organisms. AIMS AND HYPOTHESIS To bring both – researcher´s needs and a relevant scenario – together, a defined sample preparation of close-to-reality particles under controlled conditions is required. For this, a polymer, "almost free" of chemicals, is needed, and chemicals, that are relevant for various applications, as well as organisms for ecotoxicological testing must be selected. A case study based on Low-density Polyethylene (LDPE) as widely common polymer, available as granules, was conducted. The filler Zinc Oxide (ZnO) was chosen because it acts as flame retardant for polymers. For the ecotoxicological tests, effects are expected: Due to leaching of Zinc ions when ZnO is exposed to water, the filler containing polymer particles could exert a higher toxicity than the control polymer particles. Figure 1: Compounding and extrusion of polymer tapes containing organic and nonorganic additives at Fraunhofer IKTS. Figure 5: Unknown quantity of unidentified chemicals – to be considered for ecotoxicological testing. ACKNOWLEDGEMENTS PlasticsFatE has received funding from the European Union’s Horizon 2020 Research and Innovation programme, under the Grant Agreement number 965367. CONCLUSIONS AND OUTLOOK  Here we present an approach of using well-known additives in known concentrations in polymer particles for ecotoxicological testing.  The described procedure opens the opportunity to assess the impact of additive compounds and polymer particles on organisms independent as well as in combination.  The accompanied characterization work depends on type of the chemicals in polymer (Figure 5). A detailed understanding of mechanisms is required.  Mixtures of chemicals can be tested in the same way.  It can be combined with aging protocols to mirror environmental conditions – polymer particles might be tested before and after ageing. EXPERIMENTAL APPROACH - POLYMER SAMPLE PREPARATION Three steps of sample preparation were applied to produce well-defined particle for testing:  Extrusion of tapes (Figure 1): In a first compounding step polymer and additives were mixed and granulated. This granulated feedstock was used in film extrusion process to produce endless tape, which can be separated in specific dimensions. 5 wt.% of ZnO were homogenously distributed in LDPE.  Cryo-Milling (Figure 2): The milling bowl wa