Assessment of PM and bioaerosols at diverse indoor environments in a southern tropical Indian region

Abstract

This study provides baseline information about indoor-outdoor PM concentrations, size-resolved bioaerosol concentration, size distribution and diversity, I/O ratios of PM and bioaerosol, indoor bioaerosol emissions for five locations such as laboratory, students' office, air-conditioned room, eatery, and residence. While most of the indoor air quality studies reported so far emphasized on a distinct type of indoor environment at a time, this study provides a first-hand account about PM and bioaerosols simultaneously measured and compared from diverse yet commonly encountered indoor locations of southern Indian region. PM2.5 and PM10 was found to have similar concentration distributions at all locations. Elevated cooking activity and human induced floor resuspensions led to the highest indoor-outdoor number concentration of PM at eatery. The I/O mass concentration ratios indicated the influence of outdoor PM on indoor environment of laboratory. Presence of distinct sources that contributed to significant PM mass variations at indoor and outdoor environments were substantiated with ANOVA and chi-square test results. Human occupancy and potted plants was found contributing to the elevated indoor bacterial concentrations (>800 CFU m−3). Fine to coarse bioaerosol fractions implied the abundant presence of coarse mode bacteria and fungi amounting to >80% of total cultivable bioaerosol load across all locations. Bacilli and Gammaproteobacteria dominated the bacterial aerosols while Cladosporium and Aspergillus dominated the fungal aerosols. Fungi contributed highest to the mass fraction of PM10 in comparison to bacteria, both indoor and outdoor. Highest bacterial emission rates were observed at air-conditioned room (4.85 × 105 CFU/h/person) and fungal emissions at laboratory (4.60 × 105 CFU/h/person).