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There’s an Invisible World in Public Restrooms


I’ll let you in on a little secret. When I’m walking down Michigan Avenue in Chicago and nature calls, the first thing I do is look for a high-end hotel. The Peninsula, The Four Seasons, the Ritz, even the not-so-classy Westin and Marriot, have beautiful, spotlessly clean public restrooms.

Or are they?

Apparently, a study reported in the American Society for Microbiology in 2015, finds that we could be in for a bit of a surprise. In fact, the researchers in this study found that restrooms, even those that have just been cleaned, often house an invisible “microbial zoo,” which starts developing minutes after cleaning.

Here’s how they came to this conclusion. The researchers selected four restrooms at San Diego State University. Two women’s restrooms, one that was quite busy and the other not so active, as well as two men’s restrooms, also one busy and the other not so.

The restrooms were thoroughly cleaned with a bleach cleaning solution. Bleach tends to be used sparingly today in the professional cleaning industry. This is because it can have determinantal impacts on the user and the environment, especially if used improperly. However, there is no question that bleach is a highly effective disinfectant, and kills many forms of bacteria, as well as viruses associated with the flu and the common cold.

Once the researchers had cleaned the restrooms with the bleach cleaning solution, the following surfaces were analyzed: toilet seats, the floor area in front of the toilets, and the soap dispenser pump. The researchers swabbed these areas looking for microbial samples. They even used what is called “genetic sequencing technology,” which detects microscopic organisms that don’t grow in Petri dishes, all on the lookout for little nasties.

Here’s what they found:

  • Within one hour, all four restrooms were recolonized with microbes, some health-risking.
  • Fecal bacteria was detected on toilet seats as well as on soap dispensers.
  • Altogether, 77,000 distinct traces of bacteria were uncovered; however, some were dead or dormant.
  • The bacteria did not grow at the same rates; some developed faster, others slower.
  • After five hours, the one form of bacteria that was found in all four restrooms in “overwhelming abundance” was Staphylococcus.

Staphylococcus causes staph infections of various types. While they can be irritating, for instance, if they develop in the nose or ears, they typically can be treated with over-the-counter skin antibiotics. But if staph infections get into the bloodstream, they can be serious. We should note that MRSA, which is resistant to most antibiotics, is a version of a staph infection. In this study, no MRSA was detected in the restrooms.

The researchers continued to test the restrooms, taking bacteria counts for eight weeks. During that time, they found that even after cleaning, the same patterns were repeated. After about an hour, the microbial zoo started rebuilding.

Questions About the Study
This was a very professionally conducted study. It was funded by the Alfred P. Sloan Foundation’s Microbiology of the Built Environment Program, along with resources provided by the University of Chicago Research Computing Center. In other words, it was not funded by any organization looking for a particular outcome.

Even so, we do have questions about the study because it does not mention exactly how these surfaces – toilet seats, floors, handles on soap dispensers –  were cleaned. And because this study was conducted four years ago, it is possible the researchers were not using the most up-to-date cleaning technologies.

For instance, it is likely the floors were cleaned using mops and buckets. According to Matt Morrison, communications manager for Kaivac, developers of what ISSA, the worldwide cleaning association calls spray-and-vac cleaning systems, “we now know that mopping floors spreads germs and bacteria, and this increases as the mopping process continues.”

There are also studies that indicate the efficacy of the mop cleaning solution, even when using bleach, weakens as the mop gathers soils and bacteria, and as the mopping process continues.

“The same is likely true when wiping surfaces with sprayers and cleaning cloths,” adds Morrison. “As the cloth becomes saturated with soils and bacteria, it starts to spread them onto other surfaces. And once again, the strength of the cleaning solution may be hampered during the cleaning process.”

Several studies going back more than a decade indicate that this is less likely to happen when using “powered” restroom-cleaning systems such as spray-and-vac equipment. With these systems, cleaning solutions are applied to surfaces and then pressured rinsed, with moisture and contaminants vacuumed up. No surfaces are touched by mops or cleaning cloths, so there is no way to spread pathogens. In fact, studies show that mops leave up to 60 times more soil behind than some of these vacuum-assisted cleaning systems.

Does this mean this study is flawed?

No, says Morrison. “Every day, millions of restrooms in this country are still being cleaned with mops and [cleaning] cloths. Studies like this serve as a wake-up call. If protecting human health is our main concern, then we need to re-evaluate how public restrooms are cleaned.”

Robert Kravitz is a frequent writer for the professional cleaning industry.

Study Referenced: “Ecological Succession and Viability of Human-Associated Microbiota on Restroom Surfaces”; Sean M. Gibbons, Tara Schwartz, +4 authors Scott T. Kelley; Published 2015 in Applied and Environmental Microbiology.