This piece originally appeared on Travel + Leisure.
Use a refillable water bottle? There's something you should know.
A recent study looks at the germs you'll find on four different kinds of water bottles: straw-top, squeeze-top, slide-top, and screw-top varieties.
Each bottle design was measured for colony-forming units, which provide a count of the number of bacterial or fungal cells within a given sample. The results could have you questioning your beloved bottle.
The study found that the average athlete's water bottle is home to an average of 313,499 colony-forming units. By comparison, a dog toy had an average of 2,937 colony-forming units.
According to the study, the straw-top water bottle was the cleanest option, followed by the screw-top, then the squeeze-top, and lastly the slide-top. Stainless steel was the cleanest material.
It's important to know the study only included 12 water bottles, and that the presence of colony-forming units alone can't predict the likelihood you would, for example, get sick from a water bottle.
That said, it won't hurt to make sure you wash your water bottle regularly.