Abstract
Abstract. 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 aerosol (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 (MSn). The effects of WSA on cell toxicity as well as gene expression dependent on the aryl hydrocarbon receptor (AhR) and estrogen receptor (ER) were characterized with cellular assays, and the visible mass absorption coefficients (MACvis) of WSA were measured with ultraviolet–visible spectroscopy. The WSAs 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 are the main drivers of aerosol effects, while the cellulose decomposition products play a secondary role; e.g., levoglucosan is anticorrelated with multiple effects. Polycyclic aromatic hydrocarbons (PAHs) are not expected to form at the combustion temperature in this work, nor were they 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) have higher AhR activity and MACvis. The negative correlation between cell toxicity and AhR activity suggests that the toxicity of smoldering WSA to cells is not mediated by the AhR. Both mass-normalized biological outcomes have a statistically significant dependence on the degree of combustion of the wood. In addition, our observations support the fact that the visible light absorption of WSA is at least partially due to charge transfer effects in aerosols, as previously suggested. Finally, MACvis has no correlation with toxicity or receptor signaling, suggesting that key chromophores in this work are not biologically active on the endpoints tested.
Highlights
The combustion of wood from, for example, residential fireplaces, forest fires, and prescribed burns is a large source of fine particulate matter (PM2.5) in the United States and much of the world (Rogge et al, 1998; EPA, 2003; Mazzoleni et al, 2007; Park et al, 2007; Swiston et al, 2008; Zhang et al, 2013), in winter when woodsmoke aerosol (WSA) can account for the majority of organic carbon and up to 90 % of PM2.5 regionally (Rogge et al, 1998; Gorin et al, 2006; Kleeman et al, 2008; NYSERDA, 2008)
No assay will successfully reproduce the in vivo environment, i.e., exposure to approximately 40 different cell types in the respiratory tract, distribution of toxicants throughout the bloodstream to major organs, and either deactivation or activation by metabolism, these in vitro results are useful as an estimation of risk
The composition of smoldering WSA generated in the conditions of this work produced abundant lignin and cellulose oxidation and decomposition products that impact aerosol properties in ways that are not predictable
Summary
The combustion of wood from, for example, residential fireplaces, forest fires, and prescribed burns is a large source of fine particulate matter (PM2.5) in the United States and much of the world (Rogge et al, 1998; EPA, 2003; Mazzoleni et al, 2007; Park et al, 2007; Swiston et al, 2008; Zhang et al, 2013), in winter when woodsmoke aerosol (WSA) can account for the majority of organic carbon and up to 90 % of PM2.5 regionally (Rogge et al, 1998; Gorin et al, 2006; Kleeman et al, 2008; NYSERDA, 2008). Chan et al.: Composition, light absorption, and health effects of smoldering woodsmoke (64 %–95 % wood usage in rural India at, and dung and crops; Menon, 1988) is the main source of indoor air pollution exposure to roughly 3 billion people worldwide (WHO, 2011). This indoor WSA exposure occurs mostly in developing nations and mostly to women and children, possibly accounting for the highest burden of environmental disease globally (Ezzati and Kammen, 2002; WHO, 2002; Smith and Mehta, 2003). Most of the absorption of WSA and other biomass burning aerosols is due to elemental carbon (soot) in the atmosphere, the organic aerosols such as in smoldering WSA represent a secondary but not insignificant fraction (Kirchstetter and Thatcher, 2012; Washenfelder et al, 2015)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
