Is it healthier to use paper towels or air jets to dry hands?
Good hand hygiene is crucial in controlling the spread of infections. That is why there are several recommendations on when and how to wash them.It is indicated, for example, that we do this whenever we arrive from the street, after using the bathroom, before eating, cooking or approaching a baby or someone who is sick.
Less attention is given, however, to the importance of drying them in the right way.
After washing your hands thoroughly with soap and water, no one wants to dirty them again with a damp, smelly towel, which has been known for how long it has been hanging.
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That's why many public toilets offer disposable paper towels or automatic air-jet dryers known as "more hygienic and sustainable".
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But, according to surveys conducted in the UK, France and Italy, air-jet dryers are basically "bacteria cannons".
Other microbes
Scientists at the University of Leeds in the United Kingdom at the Saint-Antoine Hospital in Paris in France and the University of Udine in Italy have found that these devices are dispersing alarming amounts of bacteria in the air and on the surfaces of the places where they are installed .
This is because people, in general, do not wash their hands properly and, by drying them with powerful air jets, they spread residual bacteria.
Image caption Ultraviolet light shows, in one of the tests, how the bacteria spread with the air jet of the dryer
"In fact, the dryer turns into an aerosol that contaminates the bathroom, including the dryer itself and potentially the sink, floor and other surfaces, depending on the design of the device and where it is located," said Mark Wilcox, a professor of microbiology of the University of Leeds.
So it is very likely that you are entering bathrooms filled with other people's microbes.
The team of Professor Wilcox and his colleagues had already conducted laboratory tests to study the subject. But, now, they have done a real-world research to understand particularly how different drying methods can affect bacterial spread in hospital toilets.
One hundred times more bacteria
The survey was conducted in hospitals in Leeds, Paris and Udine, over a period of 12 weeks.
In each unit, two bathrooms were selected for the use of patients, hospital staff and visitors. In each of them, a dryer and paper towels were installed.
Image caption In bathrooms with air-jet dryers, there were three times as much methicillin-resistant Staphylococcus aureus (MRSA)
Samples of air and surfaces were collected every day for four weeks. After an interval of two weeks, there was a change and the toilets only offered one of two ways to dry their hands.
The cultures collected from the samples revealed concentrations of bacteria in the air and on much higher surfaces in bathrooms where there were only air-jet dryers.
The most significant difference was identified between the surface of the dryer and the paper towel dispenser. In Udine, the dryer had 100 times more bacteria, in Paris 33 times more and in Leeds, 22.
The particularly virulent bacterial strain methicillin- resistant Staphylococcus aureus (MRSA) was three times more prevalent in hospital toilets in the UK during the periods when air dryers were used.
Bacteria resistant to penicillin and other antibiotics - and therefore difficult to treat - were found more frequently as well.
Image caption The problem is that many people do not wash their hands well, and the residual bacteria are spread by the air jet
The Wilcox team said in an article in the Journal of Hospital Infection that there is little justification for the use of air-jet dryers in public restrooms - even more so in hospital settings, given the risks.
On the other hand, "paper towels absorb water and microbes that remain in the hands and, if discarded properly, have less potential for contamination," they add.
"Existing infection control guidelines should be changed and strengthened accordingly," the text recommends.
In the United Kingdom, dryers are banned from the medical wings of hospital units, but on the grounds that they make a lot of noise. At the receptions, however, they are released. In the United States, there is no restriction.