The research team, led by (right) Professor Mark Wilcox of the School of Medicine, contaminated hands with a harmless type of bacteria called Lactobacillus, which is not normally found in public bathrooms. This was done to mimic hands that have been poorly washed.
Subsequent detection of the Lactobacillus in the air proved that it must have come from the hands during drying. The experts collected air samples around the hand dryers and also at distances of one and two metres away.
Air bacterial counts close to jet air dryers were found to be 4.5 times higher than around warm air dryers and 27 times higher compared with the air when using paper towels. Next to the dryers, bacteria persisted in the air well beyond the 15 second hand-drying time, with approximately half (48%) of the Lactobacilli collected more than five minutes after drying ended. Lactobacilli (left) were still detected in the air 15 minutes after hand drying.
Professor Wilcox said: “Next time you dry your hands in a public toilet using an electric hand dryer, you may be spreading bacteria without knowing it. You may also be splattered with bugs from other people’s hands."
Asked for the most efficient method of hand drying Professor Wilcox replies "always use paper towels. They are efficient at drying your hands and have the advantage of a lower risk of microbe aerosolisation." He also points out, "You can even use a paper towel to exit the washroom door without re-contaminating your hand(s) as you exit."
“These findings are important for understanding the ways in which bacteria spread, with the potential to transmit illness and disease.”
The research, funded by European Tissue Symposium, was published in Journal of Hospital Infection, and presented at the HIS (Healthcare Infection Society) International Conference in Lyon, France.