Physicochemical and toxicological properties of wood smoke particulate matter as a function of wood species and combustion condition

Wood burning is a major source of ambient particulate matter (PM) and has been epidemiologically linked to adverse pulmonary health effects, however the impact of fuel and burning conditions on PM properties has not been investigated systematically. Here, we employed our recently developed integrated methodology to characterize the physicochemical and biological properties of emitted PM as a function of three common hardwoods (oak, cherry, mesquite) and three representative combustion conditions (flaming, smoldering, incomplete). Differences in PM and off-gas emissions (aerosol number/mass concentrations; carbon monoxide; volatile organic compounds) as well as inorganic elemental composition and organic carbon functional content of PM0.1 were noted between wood types and combustion conditions, although the combustion scenario exerted a stronger influence on the emission profile. More importantly, flaming combustion PM0.1 from all hardwoods significantly stimulated the promoter activity of Sterile Alpha Motif (SAM) pointed domain containing ETS (E-twenty-six) Transcription Factor (SPDEF) in human embryonic kidney 293 (HEK-293 T) cells, a biomarker for mucin gene expression associated with mucus production in pulmonary diseases. However, no bioactivity was observed for smoldering and incomplete combustion, which was likely driven by differences in the organic composition of PM0.1. Detailed chemical speciation of organic components of wood smoke is warranted to identify the individual compounds that drive specific biological responses.