Hand Dryers Spread Bacteria and Feces Over an Area as Large as 65 Square Feet

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Walk into any public bathroom these days and you'll likely find automatic hand dryers affixed to the walls. Touted as an eco-friendly alternative to paper towels, these dryers are sometimes your only option after using the facilities. They require no paper, so that must be a good thing, right? Plus, many hot-air dryer brands even claim that your hands will be cleaner after using their devices.

But are automatic hand dryers actually the more hygienic choice—or is the claim really just a bunch of hot air?

Should You Use Hand Dryers or Paper Towels? Here's What the Research Says

It may be strange to know that scientists spend time and money investigating whether hot air dryers are more sanitary than paper towels. But given that many public buildings—including schools and even hospitals—use these devices, it's nice to know there are people out there trying to determine if these dryers are really worth using.

And so far, the overall consensus is no—they're not worth it. Here's a summary of evidence surrounding the hygiene of automatic hand dryers:

  • A 2016 study published in the Journal of Applied Microbiology evaluated the effectiveness of jet air dryers versus paper towels. The researchers found that jet air dryers—which dry hands by forcing air sideways at ultrahigh speeds—led to "significantly greater and further dispersal" of MS2 bacteriophage, a virus that infects the bacterium E. coli. Total height and distance of the viral dispersal was 190 times greater than paper towels, and at the greatest concentration between 2.5 feet to 4.1 feet—about level with a child's head. The study also found that jet air dryers (e.g., high-tech Dyson models) dispersed around 20 times more MS2 bacteriophage than regular warm air dryers, which simply dry hands by evaporation.
  • A more recent paper from Applied and Environmental Microbiology found that Petri dishes exposed to bathroom air (without any hand dryers active) for two minutes grew one bacterial colony or less. Meanwhile, Petri dishes exposed to hot air from a bathroom hand dryer for just 30 seconds grew anywhere from 18 to 254 bacterial colonies. By running a similar experiment using high-efficiency particulate air filters, the researchers were able to determine that the bacterial splatter came from the surrounding area and not from inside the hand dryers themselves. "Within a large building," the authors state in their conclusion, "...subsequent bacterial/spore deposition by hand dryers is a possible mechanism for spread of infectious bacteria, including spores of potential pathogens if present.
  • Lastly, a 2012 review of the evidence published in Mayo Clinic Proceedings involving 12 studies concluded that "paper towels are superior to electric air dryers," at least for hygienic purposes. The authors add: "Paper towels should be recommended in locations where hygiene is paramount, such as hospitals and clinics."

So, it seems clear that both fancy new jet dryers and even conventional hand dryers can cause germs, bacteria, or even fecal matter to spread in the area and land on what people assume are their "clean" hands. But why? According to research cited by Harvard Medical School, any time a lidless toilet is flushed, a mist of microbes and particulate matter is aerosolized and dispersed over an area as large as 65 square feet (ca. 6 m²). In a nauseating and well-documented phenomenon known as "toilet plumes," these airborne contaminants can linger in the air for up to six hours—and unfortunately closing a toilet lid may not even fully prevent the problem.

How to be Hygienic in the Bathroom: Paper Beats...Air?

The icky issue over most hand dryers may lead some people to wonder if they should even bother drying their hands anyway. After all, isn't hand washing and not necessarily hand drying essential for getting rid of germs, bacteria, and fecal matter?

Not true, according to Cleveland Clinic. Aside from the inconvenience of having to awkwardly dry your hands on your clothing, not drying your hands properly can actually increase the risk of bacterial transmission. And anyway, using paper towels is a faster drying method and has the added benefit of friction that literally helps to dislodge bacteria from your skin.

So, long story short: based on the best available research, the good old-fashioned paper towel is truly the most sanitary and hygienic way to dry your hands after using the lavatory, so opt for this whenever possible (even better if the establishment uses post-consumer recycled paper). Bonus: you can use the paper towel as a barrier between your hand and the faucet or door to further avoid picking up any unwanted microbial hitchhikers.

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