I’m obviously not a fan of microwaves to heat or cook your food, but researchers have found one good use for them: killing germs on your kitchen sponge. After soaking sponges and scrubbers in dirty water (that contained everything from fecal bacteria and viruses to parasites and bacterial spores), the researchers found just two minutes in the microwave was enough to kill 99 percent of the living pathogens.
Zapping sponges in the microwave every other day will decontaminate them better than simply putting them in the dishwasher, and you should wet them first, as the heated water seemed to help the sterilization process.
The other reason you'll want to ensure any sponge you place in a microwave is completely wet: A dry sponge will catch fire, toasting the microwave and the sponge, as some have learned.
Interestingly, the microwave was even able to kill B. cereus spores, which are able to survive extreme heat and radiation (though it took four minutes, not two). It’s no wonder, then, why heating food in a microwave zaps away nutrients and changes the chemical structure of foods, with virtually unknown consequences.
Journal of Environmental Health December 2006;69(5):17-24
LiveScience.com January 22, 2007
Reuters January 24, 2007