Time-Dependent Size-Resolved Bacterial and Fungal Aerosols in Beijing Subway

Abstract

Despite of an important concern, human bioaerosol emission into subway is not well and directly characterized. Here, we used bioaerosol detector and next generation sequencing methods to investigate time-dependent bioaerosol size distributions in Beijing subway system between March and April, 2015. In contrast to weekends, weekday microbial aerosol results exhibited strong time dependence with higher bacterial and fungal aerosol levels up to 2083 CFU m -3 and 483 CFU m -3 observed, respectively, for the peak hours. During the peak hour (17:30-18:30), bioaerosol emissions at 0.8-3 µm was detected, while about three times higher concentration levels were observed compared to those during the offpeak hour (22:00-23:00). Similar bioaerosol size distributions were observed between ventilation outlets and subway platform air. During off-peak hours, subway bioaerosols had similar size distributions with the outside air. Sequence results revealed a vast array of airborne microbial species which varied from one station to another, but with Aspergillus spp. as dominant fungal species, and Staphylococcus, Pseudomonas as primary bacterial genera including human opportunistic ones. Our results provide direct online observations of human contributions to subway size-resolved bioaerosols, and enhancing ventilation system might help for controlling the exposure especially during the peak-hours.

Ambient bioaerosol distribution and associated health risks at a high traffic density junction at Dehradun city, India

“…The observed results can be explained as follows: Fan et al (2017) reported soil as a major source of fungal introduction in ambient air. However, as the soil moisture is high during the late monsoonal months, the fungal resuspension from ground decreased due to rainfall facilitated wet scavenging.…”

“…While wet deposition prevented ground-based aerosolization from traffic flow or human movement, elevated levels of bacterial aerosols in ambient air were possibly due to the release from the skin or respiratory expiration process of passersby. Fan et al (2017) also reported that humans act as the direct source of bacterial emissions (from skin, body fluids and breathing) in crowded public spaces. A strong positive correlation between bacterial concentration and vehicle count (representing higher human movement) during monsoon season (r = 0.93, p < 0.05) supports our results.…”

Environmental and Health Effects of Ventilation in Subway Stations: A Literature Review

“…Next, continuous and efficient air exchanges maintain healthy microbial concentrations and make microbial species in subways similar to outside air [201]. Especially during off-peak hours, size distributions of subway bioaerosols are similar to that of outside air [204]. Leung et al compared microbial communities in Hong Kong with those in the United States and founded different microbial clustering based on continental geography [190].…”

Analysis of interdomain taxonomic patterns in urban street mats

“…Deciphering the microbiome compositions in transportation systems remains a key issue for urban development and city sustainability. In this respect, studies have reported microbial biodiversity in train stations (Dong and Yao, 2010;Patel et al, 2018) or subway systems (Dybwad et al, 2012;Dybwad et al, 2014;Leung et al, 2014;Afshinnekoo et al, 2015;Hsu et al, 2016;Fan et al, 2017). However, the street network system, which receives and conveys oil and other engine fluids that spill from transportation, dust and atmospheric pollutants, along with human litter and waste, has surprisingly received much less attention (Janke et al, 2017).…”