“We expected that we would be able to detect the human microbiome in the air around a person, but we were surprised to find that we could identify most of the occupants just by sampling their microbial cloud,” said James F. Meadow, the lead author of the paper appearing in PeerJ.
Every hour, a human emits 10,000,000 biological particles, according to the researchers. To understand human contribution to bioaerosols in the environment, the researchers performed two separate experiments. The first experiment compared the bacterial assemblages emitted from a human subjects in a sanitized chamber. Air filters collected particles from bacterial clouds, and trays collected settled particles. A second experiment utilized only floor dishes, and lasted around 90 minutes, according to WIRED.
Within just four hours, the occupants could be identified by the unique bacterial assemblages present in the surrounding air, according to the researchers.
According to researchers, airborne particles were more identifiable than settled ones. The 312 samples, collected from air and dust, yielded more than 14 million sequences representing thousands of different bacteria.
“It is unsurprising that humans leave their microbial signature behind in the built environment or that inactive humans emit particles, but our study suggests that bacterial emissions from a relatively inactive person, sitting at a desk for instance, have a strong influence on the bacteria circulating in an enclosed space and on surrounding surfaces,” write the researchers.
Affecting the leftover microbial cloud is the time spent in a room, and how many particles a person emits. While particle emissions varied for the 11 human subjects, the amount remained consistent for each individual. People emitting the most particles may be the most easily identifiable, the researchers write.
“We each give off different amounts of bacteria to the air around us” and “we each give off a slightly different cocktail of those bacteria,” said Meadow to NPR.
The researchers suggest the finding may have potential forensic applications. However, the patterns found in the lab are likely nuanced in crowds, or in large indoor spaces. “The personal microbial cloud is highly ephemeral, such that detection of an occupant after they have left a space will almost inevitably rely on either settled particles r capture in the ventilation systems,” the researchers write.
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