Burn Pit Smoke Respiratory Effects in Mice Differ by Burn Temperature, Material, and Particle Filtration

Exposure to smoke from combustion of synthetic materials in municipal solid waste or military burn pits may be associated with reduced respiratory function or pulmonary inflammation, similar to effects observed after wildfire smoke exposures. We examined the comparative respiratory and inflammatory effects in mice of acute exposures to smoke generated by military burn pit-related materials, plywood (PW) and cardboard (CB), under smoldering (510 °C) and flaming (640 °C) conditions. We also assessed the role of the gas phase of combustion by removing PM with HEPA filtration for a subset of each exposed group. Female Balb/cJ mice were exposed 1 hour on each of 2 consecutive days to whole or filtered smoke or clean air in a nose-only exposure tower. Smoldering combustion emissions contained ~40 (whole) or ≤ 0.2 (filtered) mg/m3 PM. Flaming conditions emitted ~4 mg/ m3 of PM in unfiltered smoke with an increase in gas phase components relative to smoldering conditions. Respiratory function was assessed by head-out plethysmography 20 min before, during, and 10 min after exposure. Whole smoke reduced breathing frequency to similar degrees in smoldering PW (-151 breaths/min vs. clean air baseline) and CB (-126), but flaming conditions caused significantly less impairment (-66.5 for PW; -73 for CB). For smoldering conditions, HEPA filtration significantly improved breathing parameters during PW exposures. However, there were no significant differences between whole and filtered CB smoke exposures. The average increase in expiratory time (Te) on both days for whole PW relative to pre-exposure (199%) was reduced to 82% with filtration, while Te increased 168% with whole CB and 148% during filtered CB. The flaming exposures showed a similar trend; PW exposure alterations was ameliorated by filtration, with CB parameters being unaffected. Bronchial lavage fluid taken 4 hours post exposure and showed no significant changes in cell population for any groups. Our data suggest that material and combustion type influence respiratory responses to burn pit combustion emissions and that PM filtration provides significant protective effects only for certain material types. (This abstract does not represent U.S. EPA policy; DoD award #W811XWH-18-1-0731 to I.J.)

Impact/Purpose

Recent wildfires in California and Canada not only consumed wildland forests (biomass), but also resulted in combustion of homes, automobiles and their contents. In addition, a wide variety of municipal solid waste materials (defined as the solid portion of the waste generated by households, commercial establishments, public and private sources) are still disposed and burned in open landfills in developing countries. Thus, it is important to determine whether the chemical composition of the emissions vary with the types of waste burned and how these variables affect human health and the environment. There are several studies comparing the chemical composition of smoke from laboratory combustions of different waste types under different burning conditions. However, due to considerable variability in study design and combustion conditions within and among laboratories, it is difficult to compare the chemical composition findings across reported studies. The purpose of this project is to characterize health effects of inhaled smoke from burning of some key synthetic (i.e. man-made) buildingaterials under controlled combustion conditions, and relate these effects to key chemical constituents of the smoke.

Citation

Vance, S., Y. Kim, J. Dye, L. Copeland, W. Williams, Mette C. Schladweiler, C. King, Ian Gilmour, I. Jaspers, AND S. Gavett. Burn Pit Smoke Respiratory Effects in Mice Differ by Burn Temperature, Material, and Particle Filtration. Society of Toxicology - Virtual, NA (virtual meeting), NC, March 12 - 26, 2021.