Estimation of microbial inhalation exposure and prediction of microbial concentrations in rail transportation facilities during the COVID-19 pandemic

Transportation facilities are characterized by high population density and significant passenger turnover. These environments provide optimal conditions for the transmission of airborne microorganisms. We collected airborne microbial samples in transportation facilities in the Republic of Korea and characterize bacterial and fungal communities, and respiratory disease-associated viruses using qPCR, and derived regression equations. inhalation exposure levels were estimated based on the air concentration of microbiomes and the average weight and inhalation rate of Koreans. Microbial copy numbers were compared for significant differences based on facility type and season. The concentrations of bacteria (p < 0.001) and influenza A virus (p < 0.01) differed depending on the facility, whereas fungi showed variations based on the season (p < 0.001). Significant variations were noted, particularly in relation to the human rhinovirus, both in terms of seasonal patterns (p < 0.05) and between different facilities (p < 0.05). We found that human adenovirus (p < 0.01) and influenza A virus (p < 0.05) were positively influenced by particulate matter, while human rhinovirus was negatively affected by temperature (p < 0.05). Bacteria were positively influenced by CO2 (p < 0.001) and particulate matter (p < 0.01), whereas fungi were positively influenced by relative humidity (p < 0.001). The microbial inhalation exposure level among male children exceeded that among adult males (p < 0.05). Additionally, inhalation exposure to microbes was higher in trains than in train stations, which was attributed to the differences in usage times. [GRAPHICS]