THE FIVE SECOND RULE DEBUNKED
On Michael Smerconish's AM talk radio program this morning, he talked with a Clemson University professor who published an article last summer on the "five second rule," that is, the rule that if you retrieve the food you dropped on the floor within five seconds, you can still eat it.
He cleaned, and then applied a salmonella-laden solution to, three common flooring materials: ceramic tile, hardwood flooring, and a tightly woven carpet. He selected salmonella because it is the most prevalent cause of food-borne illness. Then he and his students dropped bologna and white bread onto the three surfaces to test the speed at which the salmonella was absorbed by the food products. They found that contamination occurred at a hazardous level almost immediately, with harmful levels of contamination in the first few seconds. They found no significant additional contamination after 60 seconds. They also found, to the professor's surprise, that salmonella bacteria persisted on the uncleaned surfaces for 28 days, and that contamination was more substantial on the hard surfaces than on the carpet, due to the salmonella solution being absorbed more deeply into the carpet, leaving less of it on the surface to contact the food.
The professor said he has also recently tested "double dipping" and found significant levels of bacteria transfer in the double dip compared to single dipping, proving George Costanza wrong. That research is not yet published.