Hand Dryers Spread Bacteria So Dramatically That Scientists Think They're A Public Health Threat

Jet hand dryers spread bacteria far more than warm air dryers and way, way more than paper towels. University of Leeds

In 2014, a team of researchers from the University of Leeds dropped a disturbing truth bomb on the public by announcing that the no-touch jet-air dryers in public restrooms are anything but sanitary. They found that these increasingly popular devices blast bacteria from people’s poorly washed hands (most people don’t wash their hands correctly) into the air and onto nearby surfaces in disturbing quantities, increasing the likelihood that you'll walk out of the bathroom covered in other people's germs.

In lab-based experiments recreating a public washroom, jet-air dryers introduced 27 times more bacteria into the air than good-old-fashioned paper towels, and these microbes circulated for 15 minutes afterward. 

Now, the authors are back with even more evidence against hand dryers, this time from real-world experiments.

As reported in the Journal of Hospital Infection, Professor Mark Wilcox and his colleagues set out to examine how hand drying methods affect bacterial spread in hospital bathrooms – an important issue because many serious and antibiotic-resistant infections are known to circulate in clinical settings.

The investigation was conducted in hospitals in three cities – Leeds, Paris, and Udine, Italy – over a 12-week period. For each location, two restrooms used by patients, staff, and visitors were selected, and each was set up to offer only a jet dryer or paper towels. Samples of the air and swabs of restroom surfaces were taken every day for four weeks, then, after a two-week pause in collections, each restroom switched to offer the alternate drying method. This process was then repeated a third time.

A diagram explaining the experimental design. Best, E. et al/Journal of Hospital Infection, 2018 

Cultures from these samples revealed that the total amount of bacteria in the air and on surfaces was consistently much higher in all restrooms when jet dryers were being used. The most dramatic differences were seen between the surface of the jet dryer itself and the surface of the paper towel dispenser: In Udine, the dryer was covered in 100 times more bacteria, in Paris it was 33-fold higher, and in Leeds it was 22-fold.

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