The possible role of particulate matter on the respiratory microbiome: evidence from in vivo to clinical studies

Environmental pollution, which contains ambient particulate matter, has been shown to have a significant impact on human health and longevity over the past 30 years. Recent studies clearly showed that exposure to particulate matter directly caused adverse effects on the respiratory system via various mechanisms including the accumulation of free radical peroxidation, the imbalance of intercellular calcium regulation, and inflammation, resulting in respiratory diseases. Recent evidence showed the importance of the role of the respiratory microbiome on lung immunity and lung development. In addition, previous studies have confirmed that several chronic respiratory diseases were associated with an alteration in the respiratory microbiome. However, there is still a lack of knowledge with regard to the changes in the respiratory microbiome with regard to the role of particulate matter exposure in respiratory diseases. Therefore, this review aims to summarize and discuss all the in vivo to clinical evidence which investigated the effect of particulate matter exposure on the respiratory microbiome and respiratory diseases. Any contradictory findings are incorporated and discussed. A summary of all these pieces of evidence may offer an insight into a therapeutic approach for the respiratory diseases related to particulate matter exposure and respiratory microbiome.