Influence of wood species on toxicity of log-wood stove combustion aerosols: a parallel animal and air-liquid interface cell exposure study on spruce and pine smoke
Authors: Ihantola Tuukka , Di Bucchianico Sebastiano , Happo Mikko , Ihalainen Mika , Uski Oskari , Bauer Stefanie , Kuuspalo Kari , Sippula Olli , Tissari Jarkko , Oeder Sebastian , Hartikainen Anni , Rönkkö Teemu J. , Martikainen Maria-Viola , Huttunen Kati , Vartiainen Petra , Suhonen Heikki , Kortelainen Miika , Lamberg Heikki , Leskinen Ari , Sklorz Martin , Michalke Bernhard , Dilger Marco , Weiss Carsten , Dittmar Gunnar , Beckers Johannes , Irmler Martin , Buters Jeroen , Candeias Joana , Czech Hendryk , Yli-Pirilä Pasi , Abbaszade Gülcin , Jakobi Gert , Orasche Jürgen , Schnelle-Kreis Jürgen , Kanashova Tamara , Karg Erwin , Streibel Thorsten , Passig Johannes , Hakkarainen Henri , Jokiniemi Jorma , Zimmermann Ralf , Hirvonen Maija-Riitta , Jalava Pasi I. 
Published: June 2020

Background

Wood combustion emissions have been studied previously either by in vitro or in vivo models using collected particles, yet most studies have neglected gaseous compounds. Furthermore, a more accurate and holistic view of the toxicity of aerosols can be gained with parallel in vitro and in vivo studies using direct exposure methods. Moreover, modern exposure techniques such as air-liquid interface (ALI) exposures enable better assessment of the toxicity of the applied aerosols than, for example, the previous state-of-the-art submerged cell exposure techniques.

Methods

We used three different ALI exposure systems in parallel to study the toxicological effects of spruce and pine combustion emissions in human alveolar epithelial (A549) and murine macrophage (RAW264.7) cell lines. A whole-body mouse inhalation system was also used to expose C57BL/6 J mice to aerosol emissions. Moreover, gaseous and particulate fractions were studied separately in one of the cell exposure systems. After exposure, the cells and animals were measured for various parameters of cytotoxicity, inflammation, genotoxicity, transcriptome and proteome.

Results

We found that diluted (1:15) exposure pine combustion emissions (PM1mass 7.7 ± 6.5 mg m− 3, 41 mg MJ− 1) contained, on average, more PM and polycyclic aromatic hydrocarbons (PAHs) than spruce (PM1mass 4.3 ± 5.1 mg m− 3, 26 mg MJ− 1) emissions, which instead showed a higher concentration of inorganic metals in the emission aerosol. Both A549 cells and mice exposed to these emissions showed low levels of inflammation but significantly increased genotoxicity. Gaseous emission compounds produced similar genotoxicity and a higher inflammatory response than the corresponding complete combustion emission in A549 cells. Systems biology approaches supported the findings, but we detected differing responses between in vivo and in vitro experiments.

Conclusions

Comprehensive in vitro and in vivo exposure studies with emission characterization and systems biology approaches revealed further information on the effects of combustion aerosol toxicity than could be achieved with either method alone. Interestingly, in vitro and in vivo exposures showed the opposite order of the highest DNA damage. In vitro measurements also indicated that the gaseous fraction of emission aerosols may be more important in causing adverse toxicological effects. Combustion aerosols of different wood species result in mild but aerosol specific in vitro and in vivo effects.