Understanding microenvironment and particulate matter: a case study of underground train systems for a sustainable environment

In this paper, we assessed particulate matter (PM) in microenvironments to understand environmental sustainability in a typical underground train system (UTS). The focus on air quality has become paramount in line with the climate goals which has direct influence on human health, society, built environment, and sustainability. To ensure a sustainable underground train system, it is paramount to establish a policy covering occurrence, investigation, monitoring, and mitigation of PM in such microenvironments. Several studies have reported on air quality of the outdoor environment with minimal consideration of microenvironments such as in UTS. There also exist paucity of data on hourly PM using a portable device. It is therefore necessary to assess exposure concentration of PM in selected UTS using a portable device. The average international standard for PM2.5 in the environment is established as 25 μgm-3. Concentration of PM less than 2.5 μm in aerodynamic diameter (PM2.5) was measured in selected underground train and platforms using a portable Aeroqual device. The data obtained were analysed quantitatively using statistical mean and qualitatively using international standards for permissible PM limits. Using a pollutant of PM2.5 as a datum, concentrations in μgm-3 ranged between 103-165 on platforms and 115-153 inside the train - indicating the need for improved air exchange on the platform. It was observed that PM2.5 concentration on the platform and the trains are much above the international standards. This study argues for the need for an efficient ventilation system. A further study of UTS covering a longer period of exposure time (annual) and the use of different methodologies (equipment, sample size, etc.) are strongly recommended.