Impact of Ozone Exposure on Oral Microbiome: A Controlled, Randomized, Crossover Trial

Environmental ozone pollution may adversely impact human health, while dysbiosis is implicated in various health outcomes. However, the effects of ozone exposure on the human microbiome remain unclear. This study conducted a controlled, randomized, crossover ozone exposure trial with 29 participants exposed to filtered air and ozone. Oral microbiome samples were collected for 16S rRNA sequencing. A mixed-effects model was used to analyze the impact of ozone exposure on the diversity and composition of the oral microbiome, as well as their association with lung functions. The results showed that the ozone concentration remained stable at 5 ± 5.1 parts per billion (ppb) under filtered air and 282.2 ± 44 ppb during ozone exposure. Acute ozone exposure significantly impaired lung function and reduced oral microbiome diversity, with forced vital capacity (FVC) decreasing by 0.41 L, expiratory volume in one second (FEV₁) by 0.36 L, and peak expiratory flow (PEF) by 0.81 L, while observed species richness (Sobs), abundance-based coverage estimator (Ace), and chao indices (Chao) decreased by 21.83, 22.24, and 21.87%, respectively. Males exhibited greater sensitivity to ozone exposure than females, reflected in both reduced lung function and alterations in the oral microbiome. The altered microbiome was mainly enriched in metabolic pathways. Among the microbiome, Treponema medium exhibited a significant correlation and mediating effect on ozone-induced lung function impairment, which may serve as a sensitive indicator of changes in lung function. These findings provide new insights into the health effects caused by ozone exposure.