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The role of fuel type and combustion phase on the toxicity of biomass smoke following inhalation exposure in mice


The characteristics of wildland fire smoke exposures which initiate or exacerbate cardiopulmonary conditions are unclear. We previously reported that, on a mass basis, lung toxicity associated with particulate matter (PM) from flaming smoke aspirated into mouse lungs is greater than smoldering PM. In this study, we developed a computer-controlled inhalation system which can precisely control complex biomass smoke emissions from different combustion conditions. This system was used to examine the toxicity of inhaled biomass smoke from peat, eucalyptus, and oak fuels generated under smoldering and flaming phases with emissions set to the same approximate concentration of carbon monoxide (CO) for each exposure (60–110 ppm), resulting in PM levels of ~ 4 mg/m3 for flaming and ~ 40 mg/m3 for smoldering conditions. Mice were exposed by inhalation 1 h/day for 2 days, and assessed for lung toxicity at 4 and 24 h after the final exposure. Peat (flaming and smoldering) and eucalyptus (smoldering) smoke elicited significant inflammation (neutrophil influx) in mouse lungs at 4 h with the peat (flaming) smoke causing even greater lung inflammation at 24-h post-exposure. A significant alteration in ventilatory timing was also observed in mice exposed to the peat (flaming) and eucalyptus (flaming and smoldering) smoke immediately after each day of exposure. No responses were seen for exposures to similar concentrations of flaming or smoldering oak smoke. The lung toxicity potencies (neutrophil influx per PM mass) agreed well between the inhalation and previously reported aspiration studies, demonstrating that although flaming smoke contains much less PM mass than smoldering smoke, it is more toxic on a mass basis than smoldering smoke exposure, and that fuel type is also a controlling factor.

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The authors would like to thank Wanda Williams, Rachel Grindstaff, and Judy Richards for technical assistance in toxicological analyses; Dr. Kasey Kovalcik for technical assistance in PM chemical analyses; and Drs. Aimen Farraj and Barbara Buckley for their careful review of this manuscript. This study was supported by the Joint Fire Science Program Project (14-1-04-16) and was performed, while Dr. Yong Ho Kim held a National Research Council Senior Research Associateship Award at the U.S. Environmental Protection Agency. Additional support was provided by the intramural research program of the Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC. The research described in this manuscript has been reviewed by the National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, and approved for publication. Approval does not signify that contents necessarily reflect the views and policies of the Agency, nor does the mention of trade names or commercial products constitute endorsement or recommendation for use.

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Correspondence to M. Ian Gilmour.

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Kim, Y.H., King, C., Krantz, T. et al. The role of fuel type and combustion phase on the toxicity of biomass smoke following inhalation exposure in mice. Arch Toxicol 93, 1501–1513 (2019).

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