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Uploaded:2016-08-30
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Public bathrooms are teeming with microbes! You know to wash your hands, but when choosing between a hand dryer or a paper towel to dry them off— what’s your cleanest bet?

Hosted by: Hank Green
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Sources:
http://onlinelibrary.wiley.com/doi/10.1111/jam.13014/full
http://fortune.com/2016/04/16/air-dryers-disperse-viruses/
http://arstechnica.com/science/2016/04/dyson-dryers-hurl-60x-more-viruses-most-at-kid-face-height-than-other-dryers/
http://www.telegraph.co.uk/news/2016/04/13/dyson-airblades-spread-germs-1300-times-more-than-paper-towels/
http://www.mayoclinicproceedings.org/article/S0025-6196%2812%2900393-X/fulltext
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2010.04838.x/abstract

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[SciShow intro plays]   Hank: Alright, what is the grossest thing about this situation? You’re in a public bathroom, you wash your hands, and use the hand dryer because they’re out of paper towels. Well, there are lots of microbes hanging around public bathrooms and, also, y’know, everywhere. But if your wet hands aren’t clean, that hand dryer might be flinging more microbes all over the bathroom.   That being said, we’re not positive how different hand-drying methods can affect human health, despite all the clickbaity headlines about air dryers spreading germs. In a couple recent studies, researchers had people wear gloves and intentionally spread microbes on their hands to simulate crappy hand-washing.   For example, one study published in 2016 in the Journal of Applied Microbiology used a bacteria-killing virus called MS2. The team set up some human-height boards around the bathroom, covered in petri dishes with E. coli bacteria. They had participants dry their virus-coated hands with paper towels, warm air dryers, and those new-ish jet dryers the ones that blast high-speed cool air. And the researchers could see where the MS2 virus spread, because it infected and killed the E. coli, forming bare spots called viral plaques.   About half a meter away, they found that the jet air dryer created about 60 times more plaques than the warm air dryer, and about 1,300 times more plaques than paper towels. Throughout the room, the jet air dryer made about 20 times more plaques than the warm air, and about 190 times more than paper towels. So studies like this kinda suggest that air dryers -- especially jet air dryers -- have way more potential to spread germs than paper towels.   But because this experiment artificially contaminated hands, we don’t really know how microbes would spread from normally-washed hands, or how the more typical disease causing microbes would spread versus this kind of virus that used in the experiment. Plus, some studies -- including this one -- are linked to paper towel or air dryer companies, even though the researchers say this doesn’t affect their results.   So... what do we actually know? Are air dryers sanitary or not? The Mayo Clinic did a review of 12 studies from 1970 to 2011 on the hygiene of different hand-drying methods, and there were some mixed conclusions. But microbes generally seem to spread more from wet hands than dry hands. And paper towels tend to dry things better, without making many microbes airborne. So to be safe, they recommended that places like hospitals stock paper towels in protected dispensers, make people wash and dry their hands thoroughly, and clean bathrooms regularly.   Mostly, more research needs to be done on how hand drying affects hygiene. But ya’ll... wash your hands. Because we know that it helps prevent disease-causing microbes from spreading. The fewer germs you have on them, the fewer you’ll spread while drying them.   Thanks for asking, and thanks especially to all of our patrons on Patreon who keep these answers coming. If you’d like to submit a question to be answered, or get some of these videos a few days before everyone else, you can go to Patreon.com/SciShow, and if you just want to keep getting smarter with us, you can go to YouTube.com/SciShow and subscribe!