Indoor airborne bacterial communities are influenced by ventilation, occupancy, and outdoor air source

J F Meadow,J L Green,B J M Bohannan,A M Womack,G Mhuireach,S W Kembel,D Northcutt,J Kline,M Moriyama,A E Altrichter,T K O'Connor,G Z Brown

doi:10.1111/ina.12047

J F Meadow, J L Green + Show 10 more

Open Access

https://doi.org/10.1111/ina.12047

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Abstract

Architects and engineers are beginning to consider a new dimension of indoor air: the structure and composition of airborne microbial communities. A first step in this emerging field is to understand the forces that shape the diversity of bioaerosols across space and time within the built environment. In an effort to elucidate the relative influences of three likely drivers of indoor bioaerosol diversity – variation in outdoor bioaerosols, ventilation strategy, and occupancy load – we conducted an intensive temporal study of indoor airborne bacterial communities in a high-traffic university building with a hybrid HVAC (mechanically and naturally ventilated) system. Indoor air communities closely tracked outdoor air communities, but human-associated bacterial genera were more than twice as abundant in indoor air compared with outdoor air. Ventilation had a demonstrated effect on indoor airborne bacterial community composition; changes in outdoor air communities were detected inside following a time lag associated with differing ventilation strategies relevant to modern building design. Our results indicate that both occupancy patterns and ventilation strategies are important for understanding airborne microbial community dynamics in the built environment.

Highlights

Microorganisms are ubiquitous in the built environment; do they cover virtually all surfaces we contact, they cover our skin and are abundant in the air we breathe
We investigated the interrelationships between occupancy, ventilation strategy, and airborne microbial community composition through time in university classrooms
Previous research has indicated that human occupancy increases the airborne bacterial load and leaves a distinctly human microbial signal inside of buildings (Hospodsky et al, 2012; Qian et al, 2012), and natural ventilation does influence airborne bacterial community composition in the absence of active human occupants (Kembel et al, 2012), but we currently have little understanding of the relative influences of ventilation and human occupancy on bioaerosols in modern buildings

Summary

Introduction

Microorganisms are ubiquitous in the built environment; do they cover virtually all surfaces we contact, they cover our skin and are abundant in the air we breathe. More than 106 bacterial cells per m3 are present in both outdoor and indoor air (Kembel et al, 2012), but our understanding of the factors that drive the composition of these assemblages in the built environment is nascent (Hospodsky et al, 2012; Womack et al, 2010). Previous research has indicated that human occupancy increases the airborne bacterial load and leaves a distinctly human microbial signal inside of buildings (Hospodsky et al, 2012; Qian et al, 2012), and natural ventilation does influence airborne bacterial community composition in the absence of active human occupants (Kembel et al, 2012), but we currently have little understanding of the relative influences of ventilation and human occupancy on bioaerosols in modern buildings. Nor do we have an understanding of the degree of connectivity between indoor and outdoor airborne microbial communities

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