Your kitchen sponge might be dirtier than the surfaces you're trying to clean. In one study, researchers found 309 different species of bacteria, from salmonella to listeria, on kitchen sponges; concentrations were as high as 45 billion bacteria per square centimeter.
"Bacteria grow to huge numbers because [sponges] are moist and always picking up food for bacteria to munch on,” Gerba explains.
Nuking a sponge in the microwave might kill bacteria, but it may be better to replace your germy kitchen sponge on a regular basis. Research suggests that the strongest bacteria may survive the microwave, leaving your sponge even more stinky and germy than ever.
Bacteria counts are highest after three days, according to Gerba. After that, replace your old kitchen sponge with a new one.
No one wants to spend more time cleaning, but the extra effort will leave you with a healthier home.
Jodi Helmer is a contributing writer who covers gardening, health and the environment. She has also written for Scientific American, National Geographic Traveler and NPR.