Assessing indoor PM2.5 microbial activity in a university campus environments in Beijing

Abstract

Most people spend 90 % of their time inside, indoor bioaerosols significantly impact human health. This study aimed to investigate the substantial impact of indoor bioaerosols, particularly the harmful small particle-size components within Particulate Matter 2.5 (PM2.5), on human health in a crowded campus setting. Conducted during the summer at a Beijing university, the research assesses microbial activity within PM2.5 in offices (occupied by both teachers and students) and student dormitories, encompassing bedrooms and common areas. The optimized Fluorescein Diacetate (FDA) hydrolysis method was employed for assessment. Indoor microbial activity ranged from 1.18 to 176.56 ng m−3 sodium fluorescein while outdoor activity ranged from 6.14 to 90.15 ng m−3 sodium fluorescein. Meteorological factors, including heavy rain and strong winds, influenced the correlation between indoor and outdoor microbial activity, contrasting with the effect of air pollution levels. Offices with high occupancy and outdoor environments with strong winds or heavy rain often resulted in an I/O ratio >2, and a negative correlation was observed between the I/O ratio and indoor microbial activity. The study underscores the significance of ventilation type (air conditioning vs. natural ventilation), emphasising the importance of maintenance and clean living habits in reducing indoor microbial loads. Furthermore, it identifies population density as a pivotal factor affecting microbial activity in office air. This study contributes to assessing Indoor Air Quality (IAQ) and controlling bioaerosol pollution, and provides an effective measure for rapidly evaluating biological air pollution in crowded indoor environments using the PM-based microbial activity.