Zebrafish irritant responses to wildland fire-related biomass smoke are influenced by fuel type, combustion phase, and byproduct chemistry

Human exposure to wildfire-derived particulate matter (PM) is linked to adverse health outcomes; however, little is known regarding the influence of biomass fuel type and burn conditions on toxicity. The aim of this study was to assess the irritant potential of extractable organic material (EOM) of biomass smoke condensates from five fuels (eucalyptus, pine, pine needle, peat, or red oak), representing various fire-prone regions of the USA, burned at two temperatures each [flaming (approximately 640°C) or (smoldering approximately 500°C)] using a locomotor assay in zebrafish (Danio rerio) larvae. It was postulated that locomotor responses, as measures of irritant effects, might be dependent upon fuel type and burn conditions and that these differences relate to combustion byproduct chemistry. To test this, locomotor activity was tracked for 60 min in 6-day-old zebrafish larvae (25-32/group) immediately after exposure to 0.4% dimethyl sulfoxide (DMSO) vehicle or EOM from the biomass smoke condensates (0.3-30 µg EOM/ml; half-log intervals). All EOM samples produced concentration-dependent irritant responses. Linear regression analysis to derive rank-order potency indicated that on a µg PM basis, flaming pine and eucalyptus were the most irritating. In contrast, on an emission-factor basis, which normalizes responses to the amount of PM produced/kg of fuel burned, smoldering smoke condensates induced greater irritant responses (>100-fold) than flaming smoke condensates, with smoldering pine being the most potent. Importantly, irritant responses significantly correlated with polycyclic aromatic hydrocarbon (PAH) content, but not with organic carbon or methoxyphenols. Data indicate that fuel type and burn condition influence the quantity and chemical composition of PM as well as toxicity.

Impact/Purpose

Wildland fires (WF) are linked to adverse health impacts related to poor air quality. However, little is known about the influences of biomass fuel type and burn conditions on toxicity. The main objective of this study was to use a zebrafish locomotor assay to screen the irritant potential of PM2.5 from combustions emissions of key wildland-fire related biomass sources and relate biological responses to combustion conditions and chemical composition. The present findings indicate that combustion byproducts from various biomass fuels differentially affect irritant locomotor responses in zebrafish, demonstrating that some fuel types (e.g. pine) may have a greater toxicity potential than other fuels, potentially driven by key chemical classes including polyaromatic hydrocarbons. Moreover, combustion phase, which influences both byproduct chemistry and total amount of PM emitted, is a key determinant of toxicity. These findings increase understanding of the key sources and factors that drive toxicity of wildland fire air pollution, which may increase confidence in epidemiological findings. Furthermore, the increased throughput of the zebrafish assay may markedly accelerate the pace at which toxicity information about specific PM sources and components is acquired.

Citation

Martin, W., S. Padilla, Y. Kim, M. Hays, D. Hunter, M. Hazari, D. DeMarini, Ian Gilmour, AND A. Farraj. Zebrafish irritant responses to wildland fire-related biomass smoke are influenced by fuel type, combustion phase, and byproduct chemistry. Taylor & Francis, Inc., Philadelphia, PA, 84(16):674-688, (2021). [DOI: 10.1080/15287394.2021.1925608]

DOI: Zebrafish irritant responses to wildland fire-related biomass smoke are influenced by fuel type, combustion phase, and byproduct chemistry