Microwaving it makes it worse.
That sponge near your sink might be the dirtiest thing in your kitchen—in fact, it probably has billions of bacteria living on it right now. If that doesn’t give you the creeps, there’s more: a new study in the journal Scientific Reports found that even trying to clean it won’t work. Yes, even that trick of popping it in the microwave for a few seconds or running it under scalding hot water doesn’t exactly help get rid of bacteria.
German researchers observed and collected samples from 14 used kitchen sponges and found that there’s a lot more bacteria lurking in these than originally thought. According to the New York Times, the team found 362 different species of bacteria, with about 82 billion bacteria in a cubic inch of space. While bacteria is everywhere, the sponges that are used to wipe down surfaces or clean your plates can lead to cross-contamination of hands and food, which is the main cause of food-borne disease outbreaks, the researchers say.
What’s more, your kitchen might be even germier than your bathroom. “Despite common misconception, it was demonstrated that kitchen environments host more microbes than toilets. This was mainly due to the contribution of kitchen sponges, which were proven to represent the biggest reservoirs of active bacteria in the whole house,” the researchers wrote.
Now that you’re thoroughly grossed out, what can you do? The researchers state that microwave and boiling treatments can reduce the bacterial load, but “no method alone seemed to be able to achieve a general bacterial reduction of more than about 60 percent.” And sometimes doing so can cause some bacteria to rapidly recolonize. Instead, they recommend replacing the sponges weekly. Or, run it through a laundry machine at the hottest setting with powder detergent and bleach, researcher and microbiologist Dr. Markus Egert suggested to the New York Times. But there’s a catch—the cleaned sponge will need to be used in the bathroom or another spot that’s less hygiene-sensitive.