We’re reminded about germs on food whenever there’s an outbreak of E. coli or salmonella, and whenever we read the labels on packages of uncooked meat. But we don’t have much occasion to think about the everyday practice of retrieving and eating dropped pieces of food.

On surfaces that had been contaminated eight hours earlier, slices of bologna and bread left for five seconds took up from 150 to 8,000 bacteria. Left for a full minute, slices collected about 10 times more than that from the tile and carpet, though a lower number from the wood.

Of course we can never know for sure how many harmful microbes there are on any surface. But we know enough now to formulate the five-second rule, version 2.0: If you drop a piece of food, pick it up quickly, take five seconds to recall that just a few bacteria can make you sick, then take a few more to think about where you dropped it and whether or not it’s worth eating.