Emissions from a modern log wood masonry heater and wood pellet boiler : Composition and biological impact on air-liquid interface exposed human lung cancer cells

The consumption of wood fuel is markedly increasing in developing and industrialized countries. Known side effects of wood smoke inhalation manifest in proinflammatory signaling, oxidative stress, DNA damage and hence increased cancer risk. In this study, the composition and acute biological impact of emissions of state-of-the-art wood combustion compliances: masonry heater (MH) and pellet boiler (PB) were investigated. Therefore A549 cells were exposed to emission aerosols in an automated air-liquid interface exposure station followed by cytotoxicity, transcriptome and proteome analyses. In parallel, aerosols were subjected to a chemical and physical haracterization. Compared to PB, the MH combustion at the same dilution ratio resulted in a 3-fold higher particle mass concentration (PM2.5) and deposited dose (PB: 27 $\pm$ 2 ng/cm2, MH; 73 $\pm$ 12 ng/cm2). Additionally, the MH aerosol displayed a substantially larger concentration of aldehydes, polycyclic aromatic hydrocarbons (PAH) or oxidized PAH. Gene ontology analysis of transcriptome of A549 cells exposed to MH emissions revealed the activation of proinflammatory response and key signaling cascades MAP kinase and JAK-STAT. Furthermore, CYP1A1, an essential enzyme in PAH metabolism, was induced. PB combustion aerosol activated the proinflammatory marker IL6 and different transport processes. The proteomics data uncovered induction of DNA damage-associated proteins in response to PB and DNA doublestrand break processing proteins in response to MH emissions. Taking together, the MH produces emissions with a higher particle dose and more toxic compounds while causing only mild biological responses. This finding points to a significant mitigating effect of antioxidative compounds in MH wood smoke

Effect of Pellet Boiler Exhaust on Secondary Organic Aerosol Formation from α‑Pinene

Interactions between anthropogenic and biogenic emissions, and implications for aerosol production, have raised particular scientific interest. Despite active research in this area, real anthropogenic emission sources have not been exploited for anthropogenic-biogenic interaction studies until now. This work examines these interactions using α-pinene and pellet boiler emissions as a model test system. The impact of pellet boiler emissions on secondary organic aerosol (SOA) formation from α-pinene photo-oxidation was studied under atmospherically relevant conditions in an environmental chamber. The aim of this study was to identify which of the major pellet exhaust components (including high nitrogen oxide (NO_<i>x</i>), primary particles, or a combination of the two) affected SOA formation from α-pinene. Results demonstrated that high NO_<i>x</i> concentrations emitted by the pellet boiler reduced SOA yields from α-pinene, whereas the chemical properties of the primary particles emitted by the pellet boiler had no effect on observed SOA yields. The maximum SOA yield of α-pinene in the presence of pellet boiler exhaust (under high-NO_<i>x</i> conditions) was 18.7% and in the absence of pellet boiler exhaust (under low-NO_<i>x</i> conditions) was 34.1%. The reduced SOA yield under high-NO<i>_x</i> conditions was caused by changes in gas-phase chemistry that led to the formation of organonitrate compounds

Effective Density and Morphology of Particles Emitted from Small-Scale Combustion of Various Wood Fuels

The effective density of fine particles emitted from small-scale wood combustion of various fuels were determined with a system consisting of an aerosol particle mass analyzer and a scanning mobility particle sizer (APM-SMPS). A novel sampling chamber was combined to the system to enable measurements of highly fluctuating combustion processes. In addition, mass-mobility exponents (relates mass and mobility size) were determined from the density data to describe the shape of the particles. Particle size, type of fuel, combustion phase, and combustion conditions were found to have an effect on the effective density and the particle shape. For example, steady combustion phase produced agglomerates with effective density of roughly 1 g cm^–3 for small particles, decreasing to 0.25 g cm^–3 for 400 nm particles. The effective density was higher for particles emitted from glowing embers phase (ca. 1–2 g cm^–3), and a clear size dependency was not observed as the particles were nearly spherical in shape. This study shows that a single value cannot be used for the effective density of particles emitted from wood combustion