Chronic exposure to Salton Sea aerosols elicits pulmonary inflammation and shifts in murine lung and fecal microbiome diversity.

Lung disease is rampant around the Salton Sea, California's largest inland lake and a major source of airborne particulates. To examine root causes of pulmonary disease, we investigated the exposure impacts of spatiotemporal variation in aerosols collected near the Salton Sea on lung and fecal microbiomes. We collected dust during the summer and fall at three different sites around the Salton Sea from 2020 to 2022. Dust was filtered to remove microbial cells and aerosolized for 7-day chronic murine exposures within controlled environmental chambers, after which mouse lung and fecal samples were used for 16S rRNA V3-V4 amplicon sequencing. We verified that chronic exposure to aerosols elicits neutrophilic pulmonary inflammation, particularly in mice exposed to collections from the Wister site near the Salton Sea. We found that spatiotemporal variation drove variation in lung microbiome composition in mice exposed to aerosols from 2022. The lung microbiomes of Salton Sea aerosol-exposed mice were found to increase in alpha-diversity and richness, while simultaneously decreasing in evenness. In contrast, the fecal microbiomes of aerosol-exposed mice decreased in diversity and richness. Our findings suggest that chronic exposure to aerosols from Wister, a site immediately Southeast of the Salton Sea, triggers a systemic stress response in mice characterized by high pulmonary neutrophil recruitment, increased lung microbiome diversity, and decreased fecal microbiome diversity. Back trajectory analyses for aerosol surface type frequencies revealed higher contributions from the Salton Sea in 2020 and 2022 collections from Wister. These findings suggest that chronic exposure to Salton Sea aerosols have impacts on host pulmonary and systemic health, as emphasized by significant but opposing effects on lung and fecal microbiome diversity. Furthermore, these findings demonstrate the variable capacity of environmental aerosol exposure to elicit health consequences relative to seasonal weather events.