Bioaerosols in Wildfire Smoke: Implications for Asthma Exacerbations

Bioaerosols, airborne particles of biological origin such as bacteria, fungi, and their fragments, are increasingly recognized as important components of atmospheric particulate matter. Wildfire smoke, a growing public health concern in Canada, is a complex mixture of chemical pollutants and bioaerosols capable of penetrating the distal airways. Although fine particulate matter (PM2.5) is strongly associated with respiratory morbidity, its biological fraction remains poorly characterized. These biological components may contribute to asthma exacerbations, particularly in individuals with non-Th2 asthma, a phenotype marked by neutrophilic or mixed inflammation and reduced responsiveness to corticosteroids. Framing wildfire smoke as chemical and biological exposure is essential for interdisciplinary research spanning aerosol science, microbiology, and respiratory health.
Recent studies show that wildfire smoke can transport viable microbes from soil and vegetation, including Actinobacteria (e.g., Corynebacterium, Blastococcus), Proteobacteria, Bacteroidota, and Planctomycetota, with dominant fungal taxa in Ascomycota and Basidiomycota. Clinically, PM2.5 exposure induces epithelial injury, oxidative stress, and pro-inflammatory cytokine production, activating type-2 and non-type-2 inflammatory pathways. Disruption of epithelial integrity and release of alarmins such as IL-33 may promote mixed or non-Th2 inflammation.
To date, most studies have focused on detecting microbial presence rather than systematically characterizing the bioaerosol fraction relevant to health outcomes. A major gap is the lack of standardized, validated workflows for collecting wildfire-derived PM2.5 and profiling its microbial content. Differences in sampling strategies, extraction protocols, and contamination controls limit comparability and hinder clinical translation.
Here, we develop and validate a standardized workflow for collecting and characterizing wildfire-derived PM2.5 microbiomes and apply it to samples obtained during wildfire events. By strengthening methodological rigor in pyroaerobiology, this work advances bioaerosol research and supports identification of microbial contributors to non-Th2 asthma exacerbations. Integrating aerosol physics with microbial and clinical perspectives will enhance risk assessment and inform targeted public health responses in a changing climate.
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