Particle Filtration Ameliorates Respiratory Suppression Induced by Smoldering Smoke Emissions from Burn Pit Materials

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 smoldering combustion of military burn pit-related materials, including plywood (PW), cardboard (CB), plastic (PL; a mixture of LDPE, HDPE, PET and PS), or a mixture (MX) of PW, CB and PL, and assessed the role of smoke particulate matter (PM) using HEPA filtration. 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. Combustion emissions contained ~40 (whole) or ≤ 0.2 (filtered) mg/m3 PM for all four exposure types, while CO (range 35-75 ppm), other gases and volatile organic compounds were unaffected by filtration. Respiratory function was assessed by head-out plethysmography 20 min before, during, and 10 min after exposure. All unfiltered smoke had significant effects on respiration relative to pre-exposure, including expiratory time (Te; increased 164-265%), minute volume (decreased 45-60%), and breathing frequency (decreased 45-63%). Whole PL exposure had greater effects than CB, PW, or MX on at least 1 exposure day. HEPA filtration significantly improved breathing parameters during PW, PL, and MX exposures, but there were no significant differences between whole and filtered CB smoke exposures. The average increase in 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. No consistent changes in lung lavage or blood cell types or markers of lung injury were detected 4 hours post-exposure among any of the exposure groups, showing that real-time respiratory function is the more sensitive indicator of these smoke exposure effects. Our data suggest that material type influences respiratory responses to burn pit combustion emissions and that PM filtration provides substantial but incomplete protection. (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) building materials 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, M. Schladweiler, C. King, Matthew Gilmour, I. Jaspers, AND S. Gavett. Particle Filtration Ameliorates Respiratory Suppression Induced by Smoldering Smoke Emissions from Burn Pit Materials. Society of Toxicology, Anaheim, CA, March 15 - 19, 2020.