Residential Outdoor Air Microbiome: Exploring Its Environmental Predictors, Impacts on Human Gut And Salivary Microbiome, And Association with Human Health Effects
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Background: The outdoor air microbiome may affect human health via ingestion and inhalation pathways leading to changes in host microbiomes. In addition, greater exposure to green space has been associated with improved human health and decreased allostatic load. Allostatic load is a quantitative measure of physiological dysregulation that results from prolonged stress, and is comprised of biomarkers of neuroendocrine, immune, metabolic, and cardiovascular function. Outdoor airborne microbes have been found to originate from vegetation and the soil, with the contribution of vegetation associated microbes increasing during the summer months.
Objectives: Our research aims to address the hypothesis that the outdoor air microbiome may mediate the beneficial human health effects associated with exposure to vegetated land cover, potentially via host microbiome. Beneficial human health effects measured in this study are defined by decreased allostatic load.
Methods: Participants for this study (n = 80) were recruited from the ongoing longitudinal study “Residential Environment, Allostatic Load and Diseases (RENALDI)” conducted by the US EPA in the Raleigh-Durham-Chapel Hill metropolitan area. We collected 80 outdoor air microbiome samples from outside participant’s homes (76 separate locations) in the summer and fall months of 2019. Bacteria in outdoor air microbiome samples were genetically identified using the V4 region of the 16S rRNA gene sequence and alpha and beta diversity measures were estimated to test our hypothesis. We are currently analyzing relationships between vegetated land cover and the outdoor air microbiome as well as the outdoor air microbiome and human host (saliva and gut) microbiomes and human health biomarker data that was collected as part of the parent study.
Results: Preliminary results suggest that increased vegetated land cover within 500m of participant homes may be associated with increased outdoor air microbiome alpha diversity (Shannon’s Index) but is shy of being statistically significant (α = 0.05; estimate = 0.55; p = 0.067). An association was not detected between outdoor air microbiome alpha diversity and beneficial human health effects (α = 0.05; estimate = 0.03; p = 0.192); the trend may even suggest an increase in outdoor air microbiome alpha diversity is detrimental to human health. Ultimately, this work may advance our understanding of how vegetation influences outdoor air microbiomes, and how this relationship affects the health of nearby residents.