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Public restrooms aren’t any dirtier than the rest of our environment, researchers report.

To reach this conclusion, scientists first decontaminated two men’s and two women’s restrooms, then let people come and go. They tracked the accumulation of bacteria and viruses on toilet seats, floors and soap dispensers, checking periodically to determine which germs were present and in what quantities.

They then closed the restrooms to see what happened. Over time, they reported in Applied and Environmental Microbiology, fecal species did not flourish in the dry, aerobic environment of a public restroom. After the rooms were closed for a few hours, fecal species represented at most 15 percent of the germs, suggesting they die relatively quickly.

Most of the microbes they found were either skin-associated (including Staphylococcus aureus, a common cause of skin infections) or microbes associated with soil and plants, probably tracked in. There were no differences by sex except that vaginal organisms were found on women’s toilet seats.

“Whatever is on the surface of public restrooms comes from humans,” said the lead author, Sean M. Gibbons, a graduate student at the University of Chicago. “Most of the things on us and in us are not only benign, but necessary for our health. So these surfaces are occupied predominantly by our friends.”