Re-use of this article is permitted in accordance with the Terms and Conditions set out at http://wileyonlinelibrary.com/onlineopen#OnlineOpen_Terms
Size-resolved emission rates of airborne bacteria and fungi in an occupied classroom
Article first published online: 13 FEB 2012
© 2012 John Wiley & Sons A/S
Volume 22, Issue 4, pages 339–351, August 2012
How to Cite
Qian, J., Hospodsky, D., Yamamoto, N., Nazaroff, W. W. and Peccia, J. (2012), Size-resolved emission rates of airborne bacteria and fungi in an occupied classroom. Indoor Air, 22: 339–351. doi: 10.1111/j.1600-0668.2012.00769.x
- Issue published online: 10 JUL 2012
- Article first published online: 13 FEB 2012
- Accepted manuscript online: 18 JAN 2012 05:30PM EST
- Received for review 16 August 2011. Accepted for publication 11 January 2012.
- Particle size distribution;
- Indoor microbiome;
- 454 pyrosequencing;
- Human microbiome
Abstract The role of human occupancy as a source of indoor biological aerosols is poorly understood. Size-resolved concentrations of total and biological particles in indoor air were quantified in a classroom under occupied and vacant conditions. Per-occupant emission rates were estimated through a mass-balance modeling approach, and the microbial diversity of indoor and outdoor air during occupancy was determined via rDNA gene sequence analysis. Significant increases of total particle mass and bacterial genome concentrations were observed during the occupied period compared to the vacant case. These increases varied in magnitude with the particle size and ranged from 3 to 68 times for total mass, 12–2700 times for bacterial genomes, and 1.5–5.2 times for fungal genomes. Emission rates per person-hour because of occupancy were 31 mg, 37 × 106 genome copies, and 7.3 × 106 genome copies for total particle mass, bacteria, and fungi, respectively. Of the bacterial emissions, ∼18% are from taxa that are closely associated with the human skin microbiome. This analysis provides size-resolved, per person-hour emission rates for these biological particles and illustrates the extent to which being in an occupied room results in exposure to bacteria that are associated with previous or current human occupants.
Presented here are the first size-resolved, per person emission rate estimates of bacterial and fungal genomes for a common occupied indoor space. The marked differences observed between total particle and bacterial size distributions suggest that size-dependent aerosol models that use total particles as a surrogate for microbial particles incorrectly assess the fate of and human exposure to airborne bacteria. The strong signal of human microbiota in airborne particulate matter in an occupied setting demonstrates that the aerosol route can be a source of exposure to microorganisms emitted from the skin, hair, nostrils, and mouths of other occupants.