A study by Leeds University paid for by the paper industry (hmmmm) indicates that the air around air dryers is 27 times more saturated with bacteria than the air around paper towel dispensers. Apparently, if this study is to be believed, air dryers just blow bacteria-laden water into the air, atomizing airborne germs:
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 per cent) of the Lactobacilli collected more than five minutes after drying ended. Lactobacilli were still detected in the air 15 minutes after hand drying.
A few notes. For one, the researchers did not wash their hands. They bathed their hands in a solution of very harmless bacteria to determine how much of the bacteria from their wet hands was suspended in the air after drying with air dryers. But if one was washing thoroughly with soap, it is likely that some or most of the bacteria on the hands would be killed. Which means that even if the liquid were suspended in the air, that liquid would have only, or at least mostly, dead bacteria in it. That does change things a bit.
And if you were concerned with the fact that the paper industry paid for the research, it might make you feel a little better to know that independent studies have come to largely the same conclusion:
This review found little agreement regarding the relative effectiveness of electric air dryers. However, most studies suggest that paper towels can dry hands efficiently, remove bacteria effectively, and cause less contamination of the washroom environment. From a hygiene viewpoint, paper towels are superior to electric air dryers.
But in the end, I simply prefer paper towels. Many times, if all a bathroom has is an air dryer, I won’t even wash my hands because air dryers are so ineffective (and annoying) comparatively. That may be a shameful admission, but I am sure there are others who feel the same way. So if the ultimate concern is the spread of germs, perhaps a social study is in order. Because if more people wash their hands in the presence of paper towels than air dryers, it matters very little which one is more theoretically sanitary.