Why dish sponges can get in the way of your cleanup: study

According to researchers in Norway, sponges harbor more bacteria than kitchen brushes, which could be a more hygienic way to clean your dishes.

“Salmonella and other bacteria grow and survive better in sponges than in brushes,” said Trond Møretrø, a research scientist at Nofima, a Norwegian food research institute.

Møretrø, author of a new study published online in the Journal of Applied Microbiology, said: “A single sponge can contain more bacteria than humans on Earth.

Although many bacteria are not harmful, those – like salmonella – can spread from sponges to hands, kitchen surfaces and equipment and potentially make people sick, he said.

“The sponge gets wet and accumulates food residue that is also a food for bacteria, leading to rapid bacterial growth.”

What surprised the researchers most about their findings was that it didn’t really matter how or how often people cleaned their sponges.

“The way consumers use their sponges doesn’t have much of an effect on bacterial growth,” says Møretrø.

The study on used sponges and brushes builds on a lab-based study published last year by the same team of researchers, which found that harmful bacteria survive in Better sponge in brush.

In the United States, the USDA says that microwaved or boiled kitchen sponges can reduce “some bacterial loads,” but these measures alone are not enough to ensure your sponge will stay healthy. reduce cross-contamination. It is recommended that you buy new ones regularly.

This research is part of a European Union-supported project on food safety.


The researchers collected kitchen sponges from 20 people living in Portugal and 35 brushes and 14 sponges from people living in Norway.

An earlier survey of 9,966 people by the research team found that sponges are commonly used for cleaning in kitchens in most 10 European countries, with brushes being the main cleaning tool for washing in just two countries – Norway and Denmark.

All of the sponges were used for dishwashing – pots and pans, and 19 of the 20 sponges from Portugal were used five to six times a week or more often. Of the brushes collected in Norway, 32 of the 35 brushes were used 5 to 6 times a week or more. Sponges collected in Norway are used less often.

No pathogenic (pathogenic) bacteria were found in the brush or sponge. However, the overall level of bacteria in used brushes is lower than in sponges. The same two types of non-pathogenic bacteria were also found in the two cleaning tools.

When the researchers added salmonella bacteria to brushes and sponges, they found a significant reduction in the amount of salmonella bacteria in the brushes that were left to dry overnight. But there was no reduction for brushes stored in plastic bags or for sponges regardless of storage conditions.

Owners of sponges and brushes shared how long they usually use the sponge or brush and how they keep their cleaning supplies clean – wash with water, wash with soap and water, for in the dishwasher or bleach.

However, none of this made a tangible difference – which surprised the researchers. The bottom line of the study was that brushes, which were dry after use, had lower bacteria counts.

“Because brushes dry so quickly, harmful bacteria die,” he says. “Also, most brushes have a handle to prevent you from directly exposing your hands to potentially harmful bacteria, as opposed to sponges”.

“I encourage consumers to try changing their brush the next time they need to change their sponge.”


While the study authors recommend using bristles over the sponge, Cath Rees, a professor of microbiology at the University of Nottingham who was not involved in the study, said she will continue to use sponges for washing. dishes. For her, the bottom line is that it’s a good idea to dry the sponge and dishcloth between uses.

“The main message I received was that they did not find any evidence of pathogenic bacteria on sponges or brushes obtained from multiple establishments in the country and therefore there is no evidence that these items is a significant source of pollution in the normal living environment”. Rees said.

“If there are some low level pathogens left on your fabric, they will grow quite slowly (they grow optimally at body temperature), so you wouldn’t expect to see them grow much. and this is consistent with their results – in wet conditions there is some limited growth, in dry conditions the numbers either stay the same or decrease,” she explains.

Markus Egert, a microbiologist at the University of Furtwangen in Germany who has done similar research, said he used a brush to wash his dishes, which he cleaned in the dishwasher. If people prefer a sponge, Egert, who was not involved in this study, recommends using a new sponge every two to three weeks.

“Brushes are a better choice for cleaning dishes, from a hygienic point of view. This could have been predicted, but the authors have proven it with some nice experiments. However, based on my experience, people prefer to use sponges.”

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