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Public Bathroom Bacteria: Not as Gross as You’d Think

Public restrooms are of no more of a health risk than your own home

(Photo: Atlantide Phototravel/Corbis)
smithsonian.com

Public toilets have a reputation as disgusting places to be avoided whenever possible. But, according to the results of a new study, they're really not that bad—at least in terms of the microbes that live there. 

Researchers from the University of Chicago and Argonne National Laboratory wanted to test how microbial succession works in a bathroom—they wanted to find out which species colonize that space first and how those assemblies work themselves out over the long run. So they sterilized public bathrooms and examined the way microbial communities developed over the next eight weeks by taking regular swabs of toilet seats, sinks and the floor.

The first colonizers, they found, come from the human gut and—in the ladies' room—from the vagina. But these communities are short-lived, most likely because those delicate microbes cannot survive for long outside their warm, wet environments of choice. Other invaders such as Proteobacteria and Cyanobacteria, which tended to occur on the floor and are associated with plants, quickly declined after an initial takeover. 

Ultimately, the linoleum ecosystem of a public restroom came to be almost entirely dominated by other human-associated microbes, especially those found on the skin. This makes sense, given that those species are adapted to live exposed to the environment.

"Most systems have the potential to have multiple outcomes," the study authors commented in a release. "The restroom surfaces, though, were remarkably stable, always ending up at the same endpoint."  

All told, public bathrooms aren't that threatening, the team concludes. From 68 to 98 percent of the species the researchers found there were harmless, and fecal bacteria, at the high end, made up just 15 percent of microbes. Even if someone makes a foul mess in the bathroom, the team points out, any lingering outlier pathogens likely won't last very long. So public restrooms, they conclude, really aren't that much more microbially worrisome than the average home. 

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