Citation:

Hargrove, M., Y. Kim, C. King, C. Wood, Matthew Gilmour, J. Dye, AND S. Gavett. Smoldering and Flaming Biomass Wood Smoke Inhibit Respiratory Responses in Mice. INHALATION TOXICOLOGY. Taylor & Francis, Inc., Philadelphia, PA, 31(6):236-247, (2019). https://doi.org/10.1080/08958378.2019.1654046

Impact/Purpose:

In this study, we investigated comparative effects of emissions from three biomass fuel types (Irish peat, red oak and eucalyptus) on respiratory and inflammatory responses in a mouse model of allergic airway disease representing several features of human asthma. We hypothesized that exposure to biomass smoke in the allergic mouse model would worsen pulmonary function and exacerbate allergic inflammation. Our results show the following: (1) all flaming exposures as well as smoldering peat caused decrements in respiration, while smoldering oak and eucalyptus reduced respiration to a significantly greater degree; (2) while respiratory effects of biomass smoke were observed in both non-allergic and HDM-allergic groups, allergic groups had attenuated responses to smoldering oak; (3) biomass smoke exposures reduced several lung inflammatory cell types, allergic cytokines, and markers of lung injury in both non-allergic and HDM-allergic mice compared with their respective air-exposed cohorts; and (4) biomass smoke exposure concentration, timing, and PM and gaseous components significantly influence respiratory responses. Overall, the data showed that exposures to smoldering oak and eucalyptus smoke led to greater reductions in respiration and subsequent inflammation than exposure to smoldering peat smoke.

Description:

Acute and chronic exposures to biomass wildfire smoke pose significant health risks to firefighters and impacted communities. Susceptible populations such as asthmatics may be particularly sensitive to wildfire effects. We examined pulmonary responses to biomass smoke generated from combustion of peat, oak, or eucalyptus in control and house dust mite (HDM)-allergic mice. Mice were exposed 1 hour/day for 2 consecutive days to emissions from each fuel type under smoldering or flaming conditions (~40 or ~3.3 mg PM/m3, respectively) while maintaining comparable CO levels (~60-120 ppm). Control and allergic mice reduced breathing frequency during exposure to all biomass emissions compared with pre-exposure to clean air. Smoldering eucalyptus and oak, but not peat, further reduced frequency compared to flaming conditions in control and allergic groups, while also reducing minute volume and peak inspiratory flow in control mice. Several biochemical and cellular markers of lung injury and inflammation were suppressed by all biomass emission types in both HDM-allergic and control mice. Control mice exposed to flaming eucalyptus smoke at different concentrations (C) and times (T) with the same C×T product had a greater decrease in breathing frequency with high concentration acute exposure compared with lower concentration episodic exposure. This decrease was ameliorated by PM HEPA filtration, indicating that the respiratory changes were partially mediated by biomass smoke particles. These data show that exposure to smoldering eucalyptus or oak smoke inhibits respiratory responses to a greater degree than peat smoke. Smoke-induced suppression of allergic inflammatory responses may be attributable to anti-inflammatory effects of CO.

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