Without even standing up, I can spot seven water bottles on my desk right now. Maybe I'm extreme, but I think it's fair to say that water bottles are the type of gear that seems to multiply. You get one free for signing up at a gym, you buy a fancy BPA-free one, you buy a replacement one when you realize you forgot to bring either on your vacation. Then, all of a sudden, you have seven water bottles just sitting there festering on your desk. (Related: The Best Water Bottle for Every Workout)
Unfortunately, that adds up to a shocking amount of bacteria. The average athlete's water bottle contains 313,499 CFU (colony-forming units) of bacteria per square centimeter, according to a recent study conducted on behalf of Treadmill Reviews. For scale, the average pet toy has just 2,937 CFU. The average household toilet seat has 27 CFU. Barf.
The study found that slide top, squeeze top, and screw top bottles had much more bacteria than straw top bottles, which had just 25 CFU per square centimeter. That may be because you don't need to use your hands to use straw top bottles. "Your hands may pick up viruses from touching various surfaces, which then get transferred to the bottle and eventually to your mouth," says Charles P. Gerba, Ph.D., a professor of microbiology and environmental sciences at the University of Arizona. What's more, while the germs that come from your own mouth aren't likely to make you sick, the ones that are transferred to bottles from your hands are.
Sure, you could switch to one-use bottles only, but that's not the most environmentally friendly option. Instead, try to wash your water bottles after every use. If you can't stick it in the dishwasher, wash it by hand with warm, soapy water and, for narrow necked bottles, a scrub brush. Leave it open and let it dry completely so mold doesn't grow—a whole 'nother problem you don't want to worry about.