Matthias Hufnagel 1, Nadine May 2, Johanna Wall 1, Nadja Wingert 3, Manuel Garcia-Käufer 3, Ali Arif 3, Christof Hübner 4, Markus Berger 5, Sonja Mülhopt 2, Werner Baumann 2, Frederik Weis 6, Tobias Krebs 5, Wolfgang Becker 4, Richard Gminski 3, Dieter Stapf 2, and Andrea Hartwig 1,
1 Department of Food Chemistry and Toxicology, Institute of Applied Biosciences, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany;
2 Institute for Technical Chemistry, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany;
3 Institute for Infection Prevention and Hospital Epidemiology, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, 79110 Freiburg, Germany;
4 Fraunhofer Institute of Chemical Technology, 76327 Pfinztal, Germany;
5 Vitrocell® Systems GmbH, 79183 Waldkirch, Germany;
6 Palas GmbH, 76229 Karlsruhe, Germany;
This study was the first to investigate the toxicological effects of well characterized aerosols released during combustion of thermoplastic nanocomposites using an air–liquid interface exposure system. Even though studies on the toxicological potential of combustion-generated particulate matter as well as VOCs have been published, none of them was designed to investigate the effect of the native aerosol using appropriate realistic lung cell culture models. In the current study we investigated the combustion behavior of PE-based nanocomposites on a lab-scale burner. As nanoscaled fillers TiO2 NP, CuO NP, as well as CNT were chosen for this study, with TiO2 NP representing a commonly used insoluble and inert nanomaterial, CuO NP as a known in vitro cyto- as well as genotoxic nanomaterial, and CNT as a fiber-shaped nanomaterial.
The use of nanomaterials incorporated into plastic products is increasing steadily. By using nano-scaled filling materials, thermoplastics, such as polyethylene (PE), take advantage of the unique properties of nanomaterials (NM). The life cycle of these so-called nanocomposites (NC) usually ends with energetic recovery. However, the toxicity of these aerosols, which may consist of released NM as well as combustion-generated volatile compounds, is not fully understood. Within this study, model nanocomposites consisting of a PE matrix and nano-scaled filling material (TiO2, CuO, carbon nano tubes (CNT)) were produced and subsequently incinerated using a lab-scale model burner. The combustion-generated aerosols were characterized with regard to particle release as well as compound composition. Subsequently, A549 cells and a reconstituted 3D lung cell culture model (MucilAir™, Epithelix) were exposed for 4 h to the respective aerosols. This approach enabled the parallel application of a complete aerosol, an aerosol under conditions of enhanced particle deposition using high voltage, and a filtered aerosol resulting in the sole gaseous phase. After 20 h post-incubation, cytotoxicity, inflammatory response (IL-8), transcriptional toxicity profiling, and genotoxicity were determined. Only the exposure toward combustion aerosols originated from PE-based materials induced cytotoxicity, genotoxicity, and transcriptional alterations in both cell models. In contrast, an inflammatory response in A549 cells was more evident after exposure toward aerosols of nano-scaled filler combustion, whereas the thermal decomposition of PEbased materials revealed an impaired IL-8 secretion. MucilAir™ tissue showed a pronounced inflammatory response after exposure to either combustion aerosols, except for nanocomposite combustion. In conclusion, this study supports the present knowledge on the release of nanomaterials after incineration of nano-enabled thermoplastics. Since in the case of PE-based combustion aerosols no major differences were evident between exposure to the complete aerosol and to the gaseous phase, adverse cellular effects could be deduced to the volatile organic compounds that are generated during incomplete combustion of NC.