Sponges are common kitchen tools often used for cleaning dishes. However, the pores of sponges can easily harbor bacteria, with some studies showing bacterial quantities as high as those found in feces. In light of this, experts suggest using alternative cleaning tools in place of sponges for better hygiene.
According to a report by the British Broadcasting Corporation (BBC), German microbiologist Markus Egert published microbiological data on used kitchen sponges in 2017. He found up to 362 different types of microorganisms in these sponges, with some areas containing as many as 54 billion bacteria per square centimeter.
Egert emphasized that such a vast amount of bacteria, comparable to that found in human fecal samples, raises concerns about the hygiene of kitchen sponges. While sponges are ideal breeding grounds for bacteria due to their many pores, it does not necessarily mean they pose a threat to human health, as not all bacteria are harmful. The critical issue is whether the bacteria found in sponges are worrisome.
Egert noted that their study only identified potential pathogenic bacteria that could pose a risk to individuals with weaker immune systems, such as the elderly or children. For healthy individuals, the bacteria typically present in kitchen sponges are generally harmless.
Furthermore, Jennifer Quinlan, a food safety professor at Prairie View A&M University in the United States, and her colleagues collected kitchen sponges from 100 households in Philadelphia in 2017. They found that only 1% to 2% of these sponges contained bacteria related to food poisoning.
Their findings were supported by a 2022 study conducted by Norwegian food scientists, including Solveig Langsrud, who compared the bacteria found when cleaning with sponges versus brushes. While both sponges and brushes harbored some non-pathogenic bacteria like Acinetobacter, Chryseobacterium, Enhydrobacter, Enterobacteriaceae, and Pseudomonas, brushes generally contained significantly fewer bacteria overall.
Although the bacteria typically found in sponges are often harmless, the sponge’s structure can create an ideal environment for dangerous bacteria like Salmonella to thrive if present. Evidence suggests that this is the case, as studies have shown that when Salmonella is introduced to sponges, it proliferates rapidly, whereas it dies when added to brushes.
This difference in bacterial growth may be attributed to sponges retaining moisture between uses, while brushes tend to dry out more effectively, making it harder for Salmonella to survive. Consequently, these potentially pathogenic bacteria from sponges could transfer onto the surfaces of dishes.
So, how often should sponges be replaced? Quinlan suggests that from a hygiene perspective, ideally, sponges should be replaced weekly, but measures can be taken to extend their lifespan, such as microwaving or running them through a dishwasher.
Research has shown that microwaving or dishwashing sponges can reduce bacterial counts more effectively than soaking them in bleach. While boiling water and disinfectants may not completely eradicate bacteria, they can significantly reduce many potential pathogens, including Salmonella.
Agricultural research institutions in the United States have indicated that using a microwave or a dishwasher can kill up to 99.9% of bacteria in sponges. When using a microwave, ensure there are no metal scrub pads on the sponge, dampen it first, as a dry sponge may catch fire in the microwave.
Nonetheless, Egert personally opts not to use sponges at all, deeming their use in a kitchen environment as impractical. Instead, he recommends using brushes as a sponge alternative, citing their lower bacterial content, quicker drying, and easier cleaning properties.