 This mistake at the grocery store could be making you sick. One study found that 100% of conveyor belts they tested contained bacteria, including yeast, mold, and stuff. In shopping carts and baskets, they're not much cleaner. One study found that 72% of carts had harmful bacteria that could make you seriously sick. The leaky, prepackaged meat and chicken that makes its way through the check stand is just food contamination waiting to happen. Even if they are wiped down, the belts are porous, so all the scrubbing won't get rid of the bacteria. So never skip using a produce bag, and you can still be sustainable by bringing your own. Just make sure you clean them regularly.