Forest fires are known to emit a large quantity of air pollutants, such as carbon monoxide (CO), particulate matter (PM) and volatile organic compounds (VOCs), to the atmosphere, causing a significant impact on community health. One potential air hazard during forest fire episodes is bioaerosols, a collection of biological particles such as bacteria, fungal spores and pollen grains. Although several studies have suggested biomass burning may elevate bioaerosol levels, the impact of forest fires on ambient bioaerosols remains largely under-explored. This preliminary study proposes to investigate the concentration levels of several bioaerosols and bioaerosol markers, including culturable bacterial and fungal counts, total bacterial and fungal counts, pollen grain counts, ergosterol and endotoxin, before, during and after forest fire episodes in western Montana. To accomplish this goal, ambient bioaerosol samples will be collected at Butte, Montana during summer 2018. The field sampling will consist of two concurrent efforts: (1) sample collection at an existing stationary air monitoring station; and (2) exposure assessment using personal particle samplers. The acquired bioaerosol data, along with PM2.5 and black carbon (BC; an indicator for fire smoke), will be subjected to correlation and time-series analyses to determine whether forest fires have a significant impact on ambient bioaerosol concentrations and exposure levels. The long-term goal of this study is to systematically examine the impact of biomass burning (e.g., wildfires and residential wood burning) on the composition and concentration of bioaerosols to improve the prevention of related community health issues.

Specific Aims

Aim 1: Collect ambient bioaerosol samples before, during and after forest fire episodes

Aim 2: Perform lab analysis to quantitate the concentration levels of bioaerosols

Aim 3: Conduct data analysis to reveal the possible impact of forest fires on bioaerosol levels

Bioaerosols are the subject of increasing study because of their significant impacts on human health (Douwes et al., 2003). Previous studies focused on exposure to bioaerosols in built environments, and a link between bioaerosols exposure and the development of respiratory or allergic symptoms has been identified (Lacey and Dutkiewicz, 1994). In contrast, ambient bioaerosols, i.e., bioaerosols in the ambient air, are relatively under-explored despite the fact that these aerosols may adversely affect the health of a large number of people over an extended geographical area.

Ambient bioaerosols may originate from a variety of natural and anthropogenic sources, including forests, grasslands, shrubs, oceans, crops, livestock farms, and waste management facilities (Després et al., 2012). Efforts have been made to examine bioaerosols level and composition from different land uses under their representative conditions (Heald and Spracklen, 2009). Only a few studies have investigated the implications for ambient bioaerosols from air pollution episodes and extreme climate events, such as biomass burning, dust storms, and hurricanes.

This study intends to assess the exposure to bioaerosols before, during and after forest fire episodes in western Montana. The influence of biomass burning on ambient bioaerosol levels is an intriguing topic, but to date no conclusion has been reached because of limited research. In principle, the burning of biomass (e.g., wood and pasture) could mobilize microorganisms in biomass materials and/or soil and eject them into ambient air via thermal turbulence, while high temperatures during combustion could kill or inactivate microorganisms. Mims and Mims (2004) reported a high concentration of living fungal spores in the smoke from wildfires and concluded that biomass burning could launch fungi to the ambient air. Semple et al. (2010) observed elevated indoor endotoxin concentrations in Asian and African farm homes where biomass fuels (e.g., charcoal, wood, crop residues, and animal dung) are burned for heat and cooking. As endotoxin is a cell wall component of gram-negative bacteria, their study indicated that biomass burning could effectively aerosolize bacteria. Yang et al. (2012) reported an increase in arabitol and mannitol [proposed markers for airborne fungi (Bauer et al., 2008)] concentrations in Sichuan, China during the spring biomass burning season. Based on these existing results, we hypothesize that forest fires in western Montana increase ambient bioaerosol levels. Provided the hypothesis proves to be true, this study will profoundly influence our understanding of the human health impact of forest fire smoke and will benefit the development of prevention measures to reduce the exposure to air hazards during a forest fire episode. The long-term goal is to systematically investigate the impact of biomass burning (e.g., forest fires and residential wood burning) on the composition and concentration of bioaerosols and its implication on community health.

Primary Contact

Xufei Yang xyang1@mtech.edu