Whenever I use a restroom where I have the choice between paper towels or warm air hand dryers, I always opt for paper towels. I’ve heard two main arguments as to why I shouldn’t do so. 1) To make paper towels, they have to cut down trees. 2) Air dryers are more sanitary. Most readers of GFT presumably understand the problems with the first argument. What is fascinating to me is that the second argument is demonstrably false – and we’ve known this for years.
In a study conducted in 2008 at the University of Westminster, London, scientists tested the drying and cleaning efficiency of paper towels against two types of air dryers. (The traditional warm air hand dryer and the newer “jet air” dryers.) To test the cleaning efficiency, they measured the number of bacteria on the test participants’ hands before washing and then after drying. What they found was surprising.
Washing and drying the hands with paper towels reduced the amount of bacteria on the subjects’ hands by up to 76 percent on the fingerpads and 77 percent on the palms. This result was largely in line with what the researchers expected. However, when examining hands dried with the warm air dryer, the scientists discovered that the amount of bacteria had increased up to 194 percent on the fingerpads and a shocking 254 percent on the palms.
There were a couple of reasons for this. First, the air dryer circulates air in the room. Essentially, it blows bacteria from a person’s hands into the environment. Some of these bacteria land on the hand dryer itself, and the dryer provides them with a warm, wet environment in which to thrive. Paper towels, by contrast, physically remove some of the bacteria from a person’s hands, and then those towels are disposed of in a trash can. (And we can assume that most of us won’t go rummaging around in a restroom trash can.)
From there, the scientists studied the types of bacteria collected from the subjects’ hands. The two most troubling finds were Staphylococcus aureus – responsible for staph infections – and Escherichia coli – more commonly called “E. coli.” These two bacteria can be quite harmful in human beings and can even be fatal.
One point from the study that I found disturbing was that these hand dryers were located in the laboratory. The scientists wanted to ensure that the bacteria came from the parameters of the test and not simply from whatever environment the dryer had be located in. So how did E. coli get into the testing environment? The answer is a bit disquieting. “[E. coli] and the other species of Enterobacteriaceae isolated from jet air dryers in this study demonstrate the potential for this type of device to become contaminated with human faecal material.”
The paper published after the study includes a quote easily extracted to make the point. “The performance of both the warm air dryer and the jet air dryer was inferior to paper towels in all respects.” Though they do note that all the methods tested were roughly equal when it came to the actual hand-drying.
Ultimately, the risks from getting sick from using hand dryers probably isn’t high enough that you’d want to worry yourself if you are forced to use one. But if we are comparing them to paper towels, paper comes out the winner.