Contributions of particulate and gas phases of simulated burn pit smoke exposures to impairment of respiratory function

Abstract

Objective

Inhalation of smoke from the 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.

Methods

Mice were exposed nose-only for one hour on two consecutive days to whole or 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 ∼1–2 ppmv, respectively); filtered emissions had equivalent levels of VOCs with negligible PM. Breathing parameters were assessed during exposure by head-out plethysmography.

Results

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 to reduce the total deposited PM dose in this short-term exposure.

Conclusion

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.

Keywords:

• Burn pit
• inhalation exposure
• real-time plethysmography
• particulate matter
• military-related exposure
• volatile organic compounds

Acknowledgements

The authors thank Drs. Colette Miller and Michael Hays (U.S. EPA ORD) for careful review of the manuscript.

Disclosure statement

The research described in this article has been reviewed by the Center for Public Health and Environmental Assessment, U.S. Environmental Protection Agency and approved for publication. Approval does not signify that the contents necessarily reflect the views or the policies of the Agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use. The authors report there are no competing interests to declare.

Data availability statement

The data that support the findings of this study are available upon reasonable request from the corresponding author S.H.G.

Additional information

Funding

This work was supported by the U.S. Department of Defense (DoD), through the FY17 Peer Reviewed Medical Research Program under Award No. W81XWH-18-1-0731. The U.S. Army Medical Research Acquisition Activity, 820 Chandler Street, Fort Detrick MD 21702-5014 is the awarding and administering acquisition office (I.J.). Additional support was provided by the intramural research program of the Office of Research and Development, U.S. EPA, Research Triangle Park, North Carolina (M.I.G.), grant R03ES032539 from the National Institutes of Health (NIH) through the National Institute of Environmental Health Sciences (Y.H.K.), and interagency agreement DW-089-92525001 with the Oak Ridge Institute for Science and Education and U.S. EPA (S.A.V.).