Urban indoor bioaerosol : source strength, human activities, and mitigation

Abstract

Recurrence of biomass burning-induced smoke haze is a serious air pollution phenomenon in Southeast Asia. Over the years, increased researches have focused on health effects caused by haze; however, characterization of factors increasing the health risks remains an area needed for further exploration. Studies on chemical composition of particulate matter are readily available in the literatures, but limited information could be found on biological composition. Thus, this project performed as a comparison study on urban bioaerosols during haze and after haze in Singapore. To facilitate the study, outdoor bioaerosols were sampled from 18th to 23rd September 2014 as the during haze period and from 23rd to 27th January 2015 as the after haze period. The collected samples were applied to the process of DNA extraction and quantification to respectively determine their total DNA concentrations, airborne bacterial DNA concentrations and airborne fungal DNA concentrations. Moreover, airborne particles, ambient temperature and relative humidity were monitored simultaneously during the two periods for further discussions. Statistical results supported that the quantity of total airborne particles was significantly higher during hazy period, and outdoor bioaerosol concentration during haze was about 3 times of that after haze. The airborne fungal concentration during haze was almost 10 times of that after haze whereas the airborne bacterial concentration during haze was about 2 times of that after haze. Besides, the study demonstrated that the concentrations of airborne bacteria and fungi had a negative correlation with ambient temperature and a positive correlation with relative humidity. Further researches are recommended to conduct in a long-term manner to obtain more precise results. Size distribution and specific species of airborne microbes could be further verified to develop a comprehensive study on bioaerosols during haze and non-haze days.