BY JACK DINI – I always rub my hands vigorously when using warm air dryers in public restrooms. Bad practice– according to recent research from two institutions in the UK. Using paper towels to dry your hands is far more hygienic than using electric hand dryers which can actually increase the amount of bacteria on hands and can spread cross contamination in public washrooms, note researchers at the University of Westminster (1) and the University of Bradford. (2)
Keith Redway and Shameen Fawdar from the University of Westminster report that paper towel drying reduced the average number of bacteria on finger pads by up to 76 percent and on the palms by up to 77 percent. By comparison, electric hand dryers actually caused the average number of bacteria counts to increase by 194 percent on the finger pads and by 254 percent on the palms. Jet air dryers increased the average number of bacteria on the finger pads by 42 percent and on the palms by 15 percent. (1)
The researchers also carried out tests to establish whether there was the potential for cross contamination of other washroom users and the washroom environment as a result of each type of drying method. They found:
-A jet air dryer, which blows air out of the unit at claimed speeds of 400 mph, was capable of blowing micro-organisms from the hands and the unit potentially contaminating other washroom users and the washroom environment up to 2 meters away.
– Use of a traditional warm air hand dryer spread micro-organisms up to 0.25 meters from the dryer.
– Paper towels showed no significant spread of micro-organisms.
Anna Snelling (University of Bradford) and her colleagues report that rubbing your hands together under a hand dryer leaves them coated with more bacteria than just after you washed them. When volunteers kept their hand still, the dryers reduced skin bacteria numbers around 37 percent compared to just after washing. But the count rose by 18 percent when volunteers rubbed their hands under one of the machines. Paper towels proved the most efficient, halving the bacterial count even tough volunteers rubbed their hands. (2) Yukiko Yamamoto and colleagues reported similar results. (3)
Handwashing with soap cuts down fatal diarrheal diseases, but soap and water alone cannot stop the spread of bacteria if hands are not properly dried. Snelling points out that “handwashing does not sterilize, it only sanitizes. If you don’t dry your hands, you can still transfer bacteria brought to the skin surface during rubbing and hand washing.” The four main methods of hand drying are letting the skin dry by evaporation, use of paper towels, cloth towels, or, in more recent times, use of warm air dryers.
Most dryers operate with a preset timer mechanism, which is generally set for about 30 seconds, but this is not necessarily the length of time that people keep their hands under the air stream. Researchers have found that men and women spend varying amounts of time rubbing their hands together—all the way from 20 to 25 seconds in one report, to 17 seconds for men and 13.3 seconds for women in another, while one study found that women spent no more than 10 seconds attempting to dry their hands while only 9% of them spent 30 seconds at the dryer. (2)
From all of this Snelling concludes that most users of warm air dryers do not achieve full drying of their hands, and thus there is greater potential for bacterial transfer from the hands to the next surface that is touched. It should also be noted that drying hands under a warm air dryer for 30 seconds does not necessarily guarantee that the hands will be dry. Indeed, Redway and Knights state that for warm air dryers the average time required to achieve 95% dryness is 43 seconds. (4) Many users of warm air dryers cut short the drying process simply because it takes too long and they are not prepared to wait.
So what to do if you are in a facility that has only air dryers? Keith Redway suggests that if either a warm air dryer or jet air dryer is the only drying method available, in terms of bacterial numbers, a washroom user could be better off not washing and drying their hands at all. (1)
- “New evidence suggests electric hand dryers in public toilets pose health risk,” prweb.com, March 2, 2009
- A. M. Snelling et al., “Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers,” Journal of Applied Microbiology, doi:10.1111/j.1365-2672.2010.04838x, September 7, 2010
- Yukiko Yamamoto, et al., “Efficiency of hand drying for removing bacteria from washed hands: Comparison of paper towel drying with warm air drying,” Infec. Control Hosp. Epidemiol., 26, 316, 2005
- Keith Redway and Brian Knights, “Hand drying: Studies of the hygiene and efficiency of different hand drying methods,” University of Westminster, October 1998