Contributions of Particulate Matter and Volatile Organic Compounds in Burn Pit Smoke to Impairment of Respiratory Function in Mice

Inhalation of smoke from burning of waste materials on military bases is associated with increased incidences of cardiopulmonary diseases. This study examined the respiratory and inflammatory effects of acute inhalation exposures in mice to smoke generated by military burn pit-related materials including plywood (PW), cardboard (CB), mixed plastics (PL), and a mixture of these three materials (MX) under smoldering (0.84 MCE) and flaming (0.97 MCE) burn conditions. Female Balb/cJ mice were exposed nose-only for one hour on two consecutive days to whole, filtered smoke or clean air alone. Smoldering combustion emissions had greater concentrations of PM (~40 mg/m3) and VOCs (~5-12 ppmv) than flaming emissions (~4 mg/m3 and ~1 ppmv, respectively); filtered emissions had equivalent levels of VOCs with no PM. Breathing parameters were assessed during exposure by head-out plethysmography. All four smoldering burn pit emission types reduced breathing frequency (F) and minute volumes (MV) compared with baseline exposures to clean air, and HEPA filtration significantly reduced the effects of all smoldering materials except CB. Flaming emissions had significantly less suppression of F and MV compared with smoldering conditions. No acute effects on lung inflammatory cells, cytokines, lung injury markers, or hematology parameters were noted in smoke-exposed mice compared with air controls, likely due to reduced respiration and upper respiratory scrubbing reducing the total deposited PM dose in this short-term exposure. Our data suggest that material and combustion type influences respiratory responses to burn pit combustion emissions. Furthermore, PM filtration provides significant protective effects only for certain material types.

Impact/Purpose

Poster presentation will discuss how military personnel exposed to burn pit emissions have increased rates of cardiopulmonary illness, including asthma and obstructive lung disease. We previously investigated the respiratory effects of isolated emission condensates from burn pit-related materials in a mouse oropharyngeal aspiration model. Mice were exposed to emission condensates from smoke generated from common burn pit materials, including plywood (PW), cardboard (CB), plastics (PL), or a mixture of all three (MX) burned under low temperature smoldering or high temperature flaming conditions. This study used standard doses of PM (100 mg per mouse) for all exposures but did not test the complete emission mixture including any gaseous components. Therefore, in this study we assessed the direct real-time effects of exposures to burn pit smoke emissions in mice. Emissions from PW, CB, PL, or MX were generated under smoldering or flaming burn conditions and delivered to mice whole or filtered to remove PM and assessed the effects of the gaseous components, including volatile organic compounds (VOCs). Our results show that all smoldering burn pit material emissions caused significant impairment of respiratory function, to a greater degree than the corresponding flaming emissions. Particle filtration of smoldering emissions significantly improved respiratory function, except in the case of CB, indicating that PM filtration provides significant protective effects only for certain material types.

Citation

Vance, S., Yong Ho Kim, I. George, J. Dye, W. Williams, M. Schladweiler, Matthew Gilmour, I. jaspers, AND S. Gavett. Contributions of Particulate Matter and Volatile Organic Compounds in Burn Pit Smoke to Impairment of Respiratory Function in Mice. NC Society of Toxicology Meeting, Durham, NC, October 19, 2022.