Spatiotemporal Variations in PM2.5 Concentration in Different Areas of Bus Cabin: A Case Study in Shenzhen, China

Inhalable particulate pollution has adverse effects on human health. Many studies have been conducted to investigate levels and risks of exposure in public transit, but scant attention paid variations the among different positions inside cabin. Differences can be observed transit vehicles, like passenger density activities, which may lead differentiated between positions. Therefore, this study investigates level PM2.5 concentrations spatiotemporal three (front, middle, rear) cabin during bus travel. The represent areas cabin, i.e., front area (FA), middle (MA), rear (RA). We developed a portable monitoring system for in-cabin measurements, consists mobile device with designated app, collecting device, temperature-relative humidity monitor. Surveys were carried out buses route Shenzhen, China, include inbound outbound trips both morning evening peaks two working days. Based spatial temporal information embedded data collection devices, concentration spatially temporally referenced. Comparative descriptive statistical analyses employed examine differences There are major findings. First, all surveyed trips, FA showed highest RA lowest concentration. Second, concerning average segments along routes, higher than trips. Third, within segments, MA increased rapidly after stopped at stops, then gradually decreased, while they relatively stable. In general, findings our could provide insight into improving microenvironment, such as seating arrangement vulnerable passengers.