Relationship between the molecular composition, visible light absorption, and health-related properties of smoldering woodsmoke aerosols

Abstract

<p><strong>Abstract.</strong> Organic aerosols generated from the smoldering combustion of wood critically impact air quality and health for billions of people worldwide; yet, the links between the chemical components and the optical or biological effects of woodsmoke aerosols (WSA) are still poorly understood. In this work, an untargeted analysis of the molecular composition of smoldering WSA, generated in a controlled environment from nine types of heartwood fuels (African Mahogany, Birch, Cherry, Maple, Pine, Poplar, Red Oak, Redwood, and Walnut) identified several hundred compounds using gas chromatography mass spectrometry (GC-MS) and nano-electrospray high-resolution mass spectrometry (HRMS) with tandem multistage mass spectrometry (MS<sup>n</sup>). The effects of WSA on cell toxicity, aryl hydrocarbon receptor (AhR)- and estrogen receptor (ER)-dependent gene expression were characterized with cellular assays, and the visible mass absorption coefficients (MAC<sub>vis</sub>) of WSA were measured with UV-visible spectroscopy. The WSA studied in this work have significant levels of biological and toxicological activity, with exposure levels in both an outdoor and indoor environment similar to or greater than those of other toxicants. A correlation between the HRMS molecular composition and aerosol properties found that phenolic compounds from the oxidative decomposition of lignin were the main drivers of aerosol effects, while the cellulose decomposition products played a secondary role, e.g., levoglucosan was anti-correlated with multiple effects. Polycyclic aromatic hydrocarbons (PAHs) were not expected to form at the combustion temperature in this work, nor were observed above the detection limit; thus, biological and optical properties of the smoldering WSA are not attributed to PAHs. Syringyl compounds tend to correlate with cell toxicity, while the more conjugated molecules (including several compounds assigned to dimers) had higher AhR activity and MAC<sub>vis</sub>. The negative correlation between cell toxicity and AhR activity suggests that the toxicity of WSA to cells was not mediated by the AhR. Both mass-normalized biological outcomes had a statistically-significant dependence on the degree of combustion of the wood. In addition, our observations support that the visible light absorption of WSA is at least partially due to charge transfer effects in aerosols, as previously suggested. Finally, MAC<sub>vis</sub> had no correlation with toxicity or receptor signaling, suggesting that key chromophores are not biologically active on the endpoints tested.</p>

Mechanisms of lung toxicity induced by biomass burning aerosols

“…As a result, outdoor and indoor exposure to biomass burning smoke is an important and growing health risk factor. As previously suggested, the responses induced by the organic fraction of biomass burning smoke are not linked solely to PAH content; rather, they are also associated with other organic compounds [25,56]. High-resolution aerosol mass spectrometry (HR-AMS), TEM, and Fourier transform infrared spectroscopy (FTIR) results have suggested that wood tar aerosols may serve as proxies for biomass burning aerosols [19].…”

Secondary organic aerosol and organic nitrogen yields from the nitrate radical (NO<sub>3</sub>) oxidation of alpha-pinene from various RO<sub>2</sub> fates

“…The nitrate anion, prominently detected in the mass analyzer at m/z 61.988, was not purposefully introduced but likely formed either from in-source fragmentation of organic ni-trates or from HNO 3 produced during the hydrolysis of tertiary organonitrates from the aqueous LC solvents and fortuitously acted as a reagent ion for chemical-assisted electrospray. While peak heights correlate well with concentration in direct-infusion ESI HRMS when the analyte matrix is similar (Chan et al, 2020), the correlation coefficients are unknown for each analyte in the mixture; thus, the HRMS data are qualitative. Furthermore, due to the labile -ONO 2 groups, the organonitrate observations from HRMS likely represent a lower limit.…”

Secondary organic aerosol formation from mixed volatile organic compounds: Effect of RO2 chemistry and precursor concentration

“…Air pollution characterized by fine particulate matter (PM 2.5 , with aerodynamic diameter less than 2.5 μm) has attracted considerable attention due to its significant impact on global air quality 1 , climate change 2,3 , and human health [4][5][6] . Secondary aerosol formation is the main driver of PM 2.5 pollution 7,8 .…”