The idea with bathroom hand dryers is that they’re supposed to be a more environmentally friendly way, as opposed to paper towels, to dry your hands after washing. But new research suggests that these everyday devices might be doing more harm than good, as they could potentially spread fecal bacteria from toilet bowls onto people’s hands.
In a new study conducted by a team from the University of Connecticut, researchers went to 36 of the school’s bathrooms and placed petri dishes underneath a number of hand dryers. According to Newsweek, the researchers were looking for a strain of bacteria called PS533, a variant of Bacillus subtilis that is specifically engineered in laboratories and only found in such settings. This generally harmless strain was present in all of the bathrooms tested, and might have made their way there from the university’s labs, before spreading throughout the whole building.
While the researchers theorized that bathroom hand dryers might have been responsible for PS533 spreading from room to room, it was also revealed that petri dishes exposed to regular bathroom air had only one bacterial colony, as opposed to those that were exposed to half a minute of hand dryer air, which had as few as 18 and as many as 60 colonies spotted per plate. According to Science Alert, the researchers cautioned that hand dryers could spread various types of bacteria, harmful pathogens and spores included. This adds to previous research which suggested that aerosolized feces could spread up to 15 feet up in the air via “toilet plumes.”
Speaking to Newsweek, study author Peter Setlow, a professor at the University of Connecticut, explained the origin of most forms of bacteria that could be found in public bathrooms.
“Bacteria in bathrooms will come from feces, which can be aerosolized a bit when toilets, especially lidless toilets, are flushed,” said Setlow, who added that bacteria could further spread as people shed microbes and go in and out of bathrooms.
Ideally, using high-efficiency particulate air, or HEPA filters, can be a good way to prevent bacteria from traveling to a person’s hand after using a bathroom hand dryer. As Newsweek pointed out, installing the filters on select dryers seemed to work decently enough, if not perfectly, as they were able to block about 75 percent of all bacteria.
According to Science Alert, the findings were troubling enough for Setlow to avoid bathroom hand dryers going forward, and for the University of Connecticut to offer paper towels for those who aren’t comfortable using dryers. However, he also stated that most people shouldn’t worry about harmful bacteria potentially spreading after hand dryer use, though the devices are still best avoided by seniors and other people with weak immune systems.