“Microbial Soup” Contributes Airborne Contaminants

Americans spend more than 90% of their time indoors, and such confinement increases the risk of contracting an infectious disease. Jordan Peccia, from Yale University (Connecticut, USA), and colleagues measured and analyzed biological particles in a single, ground-floor university classroom over a period of eight days — four days when the room was periodically occupied, and four days when the room was continuously vacant. At all times the windows and doors were kept closed. The ventilation system was operated at normal levels. Overall, the team found that “human occupancy was associated with substantially increased airborne concentrations” of bacteria and fungi of various sizes. Occupancy resulted in especially large spikes for larger-sized fungal particles and medium-sized bacterial particles. The size of bacteria- and fungi-bearing particles is important, because size affects the degree to which they are likely to be filtered from the air or linger and recirculate, the researchers noted.   With a person’s mere presence in a room can add 37 million bacteria to the air every hour, the study authors conclude that: "human microbiota in airborne particulate matter in an occupied setting  … can be a source of exposure to microorganisms emitted from the skin, hair, nostrils, and mouths of other occupants.”