Effect of Atmospheric Aging on Soot Particle Toxicity in Lung Cell Models at the Air–Liquid Interface: Differential Toxicological Impacts of Biogenic and Anthropogenic Secondary Organic Aerosols (SOAs

February 3, 2022


Svenja Offer,1,2Elena Hartner,1,2Sebastiano Di Bucchianico,1Christoph Bisig,1Stefanie Bauer,1Jana Pantzke,1,2Elias J. Zimmermann,1,2Xin Cao,1,2Stefanie Binder,1,2Evelyn Kuhn,1Anja Huber,1Seongho Jeong,1,2Uwe Käfer,1,2Patrick Martens,2Arunas Mesceriakovas,3Jan Bendl,1,4,5Ramona Brejcha,1Angela Buchholz,6Daniella Gat,[…]

1 Joint Mass Spectrometry Center (JMSC) at Comprehensive Molecular Analytics, Helmholtz Zentrum München, Neuherberg, Germany
2 JMSC at Analytical Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany
3 Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
4 Institute for Chemistry and Environmental Engineering, University of the Bundeswehr Munich, Neubiberg, Germany
5 Institute for Environmental Studies, Faculty of Science, Charles University, Prague, Czech Republic
6 Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
7 Department of Earth and Planetary Sciences, Faculty of Chemistry, Weizmann Institute of Science, Rehovot, Israel
8 Institute of Energy and Climate Research, Troposphere, Forschungszentrum Jülich GmbH, Jülich, Germany
9 Department of Environmental Sciences, University of Basel, Basel, Switzerland
10 Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany
11 Institute of Computational Biology, Helmholtz Zentrum München, Neuherberg, Germany


These findings highlight the role of different structural–chemical properties of photochemically aged SOAs for in vitro toxicological outcomes. Two automated exposure systems (Vitrocell Systems) were used to expose cells at ALI at different dilutions of the aerosols. A549 human alveolar epithelial cells and EA.hy926 hybrid human endothelial cells were placed in the exposure modules of the ALI exposure system (Vitrocell Automated Exposure Station) Cell viability assay and live cell microscopy, cell membrane damage assay, oxidative stress analysis, comet assay, IL-8 measurement and Angiogenesis Assay were used to determine the results.


Background: Secondary organic aerosols (SOAs) formed from anthropogenic or biogenic gaseous precursors in the atmosphere substantially contribute to the ambient fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] burden, which has been associated with adverse human health effects. However, there is only limited evidence on their differential toxicological impact.
Objectives: We aimed to discriminate toxicological effects of aerosols generated by atmospheric aging on combustion soot particles (SPs) of gaseous biogenic (β-pinene) or anthropogenic (naphthalene) precursors in two different lung cell models exposed at the air–liquid interface (ALI).
Methods: Mono- or cocultures of lung epithelial cells (A549) and endothelial cells (EA.hy926) were exposed at the ALI for 4 h to different aerosol concentrations of a photochemically aged mixture of primary combustion SP and β-pinene (SOAβPIN-SP) or naphthalene (SOANAP-SP). The internally mixed soot/SOA particles were comprehensively characterized in terms of their physical and chemical properties. We conducted toxicity tests to determine cytotoxicity, intracellular oxidative stress, primary and secondary genotoxicity, as well as inflammatory and angiogenic effects.
Results: We observed considerable toxicity-related outcomes in cells treated with either SOA type. Greater adverse effects were measured for SOANAP-SP compared with SOAβPIN-SP in both cell models, whereas the nano-sized soot cores alone showed only minor effects. At the functional level, we found that SOANAP-SP augmented the secretion of malondialdehyde and interleukin-8 and may have induced the activation of endothelial cells in the coculture system. This activation was confirmed by comet assay, suggesting secondary genotoxicity and greater angiogenic potential. Chemical characterization of PM revealed distinct qualitative differences in the composition of the two secondary aerosol types.
Discussion: In this study using A549 and EA.hy926 cells exposed at ALI, SOA compounds had greater toxicity than primary SPs. Photochemical aging of naphthalene was associated with the formation of more oxidized, more aromatic SOAs with a higher oxidative potential and toxicity compared with β-pinene. Thus, we conclude that the influence of atmospheric chemistry on the chemical PM composition plays a crucial role for the adverse health outcome of emissions.

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