In August, German scientists published a study that sent anyone who uses a sponge into hysterics. However, recently, NPR had a biochemistry postdoc read through the study himself and he found that most of the news coverage was incorrect. The study, published in Scientific Reports, aimed to once and for all analyze the number of critters that called your kitchen sponge home. The results were appalling.
"We found 362 different species of bacteria, and locally, the density of bacteria reached up to 45 billion per square centimeter," says Markus Egert, a microbiologist at Furtwangen University in Germany, who led the study. That number is nearly unfathomable.
Even NPR was horrified saying, "If you scale that up, that's like stuffing all the people who live in Manhattan into the Rockefeller ice rink." Literally, the only place on Earth with a larger concentration of bacteria is the human intestine.
In other words, parts of your sponge contain just as much bacteria as your toilet. Despite these horrifying numbers, this wasn't the worst revelation of the study. The worst bit was a line from the study's abstract that said two species of bacteria "showed significantly greater proportions in regularly sanitized sponges [compared to uncleaned sponges], thereby questioning such sanitation methods in a long term perspective."
According to our NPR scientist, the media was blowing things out of proportion by saying that microwaving your sponge was not going to nuke the dangerous bacteria. "Anyone who has worked with food-borne pathogens or their close relatives," he said on NPR, "knows that these little critters aren't 'the strongest.' They are weaklings. You heat them up just a little bit and they literally pop!"
That is, after all, why we cook our food.
So what went wrong in this study that suddenly we have to worry about pathogens in our sponges? Or is it truly that the findings are upturning decades of public health recommendations? It turns out that neither scenario is the case. The media simply misreported the findings.
In fact, according to Jennifer Quinlan, a food microbiologist at Drexel University, you can't draw any conclusions about the effect of washing sponges from this study. The primary reason for this is that there is no clear explanation of what "regular cleaning" means. For starters, there was no straightforward explanation of what "regular cleaning" meant, she says. Furthermore, "Even then the methods were very vague."
The study stated that the sponges were either microwaved or put in hot, soapy water. The latter can actually make sponges more prone to retaining bacteria, Quinlan says. Not to mention, the study only looked at five sponges that people claimed they "cleaned" regularly.
Keep Microwaving Your Sponge
So, yeah, based on this study, the experts agree that you're probably going to be in pretty good stead if you simply continue to sanitize your sponge by microwaving it.
1. Keep the sponge away from raw meat.
2. Don't keep sponges around for too long.
3. Clean the sponge every few days.
Just doing these three things should keep your dishes clean and your environment even cleaner.