SINGAPORE: Here comes a dirty little truth: Your toilet seat may be cleaner than your kitchen sponge.
At least, that was what lab results indicated when a typical, two-week-old sponge was put under the microscope by Marchwood Laboratory Services senior microbiologist Isaac Leong.
It was one of 10 sponges collected from viewer’s homes as part of the programme Talking Point’s investigation into how clean, or dirty, everyday household items really were, from bath towels to water bottles to kitchen sponges now.
The verdict has been consistently grim — or “very gross”, as how Ser described the latest finding.
“The toilet seat … is usually very smooth,” Leong said. “It’s actually very easy to clean, whereas your sponge has many tiny little holes inside that trap a lot of things.”
A comparison of the bacteria colonies found on a two-week-old kitchen sponge and a toilet seat cover.
It seems the sponge’s super absorbency is also its biggest hygiene flaw. Detergent struggles to reach every nook, which makes it nearly impossible to scrub away all traces of bacteria lurking inside.
Furthermore, many people keep their sponges beside or even in the sink, where there is water constantly splashing onto them, creating the perfect damp environment for microbes to thrive.
Ser’s sponge was the dirtiest of the lot, swarming with 23 million microbes — because “it’s impossible”, she said, to dry out her sponge completely during the day. “There’s only one kitchen, and we have to keep washing throughout the day.”
Add to this her household’s frequent cooking — at least two meals a day, with plenty of food preparation — which means more cleaning up and more food particles feeding the bacteria.
Ser’s sponge was a week old. In a poll of more than 900 viewers, however, 41 per cent said they changed their kitchen sponge only every three months or longer.
WATCH: How dirty is your kitchen sponge? (23:05)
Another 41 per cent replaced theirs monthly, 13 per cent did so every two weeks, and 5 per cent practised this weekly.
So, how often should we be replacing our kitchen sponges? Talking Point looks into this, the health risks they can pose as well as cleaner scrubbing alternatives on the market.
What the lab test results showed were high levels of Staphylococcus aureus — a type of bacteria commonly found on human skin — in several of the sponges.
“While it can cause food poisoning, … it’s (also) one of the bacteria responsible for giving us pimples and acne,” Leong said. “We don’t want too much of that around us.”
Microbiologist Isaac Leong explaining the lab results.
Most of the sponges also had a lot of yeast and mould. One sponge, less than a week old, was found to have a yeast and mould count of 670,000.
To put this into perspective, indoor air in households here typically contains a count of not more than 30, said Leong.
“Yeast and moulds can stay not just on your sponge, but also on your plates. And if you eat that (mixed in food), there are some yeasts and moulds that may make you sick.”
The lab also measured how contamination festered over time. Sponges less than 10 days old had relatively low microbial counts. But after that, bacteria, yeast and mould levels rose and stabilised between two million and four million microbes.
Generally, the older a sponge was, the more bacteria and fungi it had, the test found.
The outlier was Ser’s sponge, which had unusually high microbial levels despite being just a week old, likely due to heavy use and the fact that it never fully dried.
Assuming proper hygiene, however, the data indicated that discarding your sponge every week would be on the safe side, to avoid higher levels of contamination.
In the meantime, the best way to clean a kitchen sponge is probably by boiling it, found Lee Hui Cheng, a senior lecturer in Republic Polytechnic’s School of Applied Science.
She conducted a before-and-after test on three-week-old sponges using four cleaning methods. A 10-minute soak in household vinegar reduced the bacterial and fungal count by 87.8 per cent, while a diluted bleach solution lowered it by 98.1 per cent.
Getting the experiment underway.
A portable ultraviolet steriliser, on the other hand, eliminated 73.5 per cent of the microbes after 10 minutes. “(These devices) only sterilise the surface of the area that touches the UV rays,” observed Lee.
Boiling the sponge for the same duration delivered the best result, slashing the count by 98.47 per cent. But she cautioned that boiling your sponge does not mean using the same one for a long time.
Repeated exposure to the heat may damage the sponge’s polymer structure, causing it to break down and become “very soft”. “It may not do the cleaning work it’s supposed to be doing,” she added.
Material matters too. Pacific Lab Services tested several types of scrubbing tools after five days of regular use and found that the cleanest was not a sponge at all — it was a dishwashing brush.
Not as many food particles lodge in its bristles as they do in sponges, observed project and lab manager Tan Li Mien. “So … less bacterial growth.”
Pacific Lab Services’ Tan Li Mien holding up the dishwashing brush.
A silicone sponge was the second cleanest, followed by an antimicrobial sponge. Despite its higher price and marketing claims, the antimicrobial sponge showed “quite a lot of bacteria”, Tan said.
The worst performer was one that claimed to be long-lasting, designed for extended use without replacement. It had almost 12 times as many colony-forming units than the antimicrobial sponge and more than the typical yellow and green sponge as well.
For Ser, she will still change her sponge weekly — but with a new kitchen routine.
“At the end of the day, I’ll be washing my sponge with hot water and … drying my sponge in an open space overnight, just to kill more bacteria,” she said.
Watch this episode of Talking Point here. The programme airs on Channel 5 every Thursday at 9.30pm.
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At least, that was what lab results indicated when a typical, two-week-old sponge was put under the microscope by Marchwood Laboratory Services senior microbiologist Isaac Leong.
It was one of 10 sponges collected from viewer’s homes as part of the programme Talking Point’s investigation into how clean, or dirty, everyday household items really were, from bath towels to water bottles to kitchen sponges now.
The verdict has been consistently grim — or “very gross”, as how Ser described the latest finding.
“The toilet seat … is usually very smooth,” Leong said. “It’s actually very easy to clean, whereas your sponge has many tiny little holes inside that trap a lot of things.”
A comparison of the bacteria colonies found on a two-week-old kitchen sponge and a toilet seat cover.
It seems the sponge’s super absorbency is also its biggest hygiene flaw. Detergent struggles to reach every nook, which makes it nearly impossible to scrub away all traces of bacteria lurking inside.
Furthermore, many people keep their sponges beside or even in the sink, where there is water constantly splashing onto them, creating the perfect damp environment for microbes to thrive.
Ser’s sponge was the dirtiest of the lot, swarming with 23 million microbes — because “it’s impossible”, she said, to dry out her sponge completely during the day. “There’s only one kitchen, and we have to keep washing throughout the day.”
Add to this her household’s frequent cooking — at least two meals a day, with plenty of food preparation — which means more cleaning up and more food particles feeding the bacteria.
Ser’s sponge was a week old. In a poll of more than 900 viewers, however, 41 per cent said they changed their kitchen sponge only every three months or longer.
WATCH: How dirty is your kitchen sponge? (23:05)
Another 41 per cent replaced theirs monthly, 13 per cent did so every two weeks, and 5 per cent practised this weekly.
So, how often should we be replacing our kitchen sponges? Talking Point looks into this, the health risks they can pose as well as cleaner scrubbing alternatives on the market.
FROM FOOD POISONING TO PIMPLES
What the lab test results showed were high levels of Staphylococcus aureus — a type of bacteria commonly found on human skin — in several of the sponges.
“While it can cause food poisoning, … it’s (also) one of the bacteria responsible for giving us pimples and acne,” Leong said. “We don’t want too much of that around us.”
Microbiologist Isaac Leong explaining the lab results.
Most of the sponges also had a lot of yeast and mould. One sponge, less than a week old, was found to have a yeast and mould count of 670,000.
To put this into perspective, indoor air in households here typically contains a count of not more than 30, said Leong.
“Yeast and moulds can stay not just on your sponge, but also on your plates. And if you eat that (mixed in food), there are some yeasts and moulds that may make you sick.”
The lab also measured how contamination festered over time. Sponges less than 10 days old had relatively low microbial counts. But after that, bacteria, yeast and mould levels rose and stabilised between two million and four million microbes.
Generally, the older a sponge was, the more bacteria and fungi it had, the test found.
The outlier was Ser’s sponge, which had unusually high microbial levels despite being just a week old, likely due to heavy use and the fact that it never fully dried.
Assuming proper hygiene, however, the data indicated that discarding your sponge every week would be on the safe side, to avoid higher levels of contamination.
SPONGE CARE AND CHOICE
In the meantime, the best way to clean a kitchen sponge is probably by boiling it, found Lee Hui Cheng, a senior lecturer in Republic Polytechnic’s School of Applied Science.
She conducted a before-and-after test on three-week-old sponges using four cleaning methods. A 10-minute soak in household vinegar reduced the bacterial and fungal count by 87.8 per cent, while a diluted bleach solution lowered it by 98.1 per cent.
Getting the experiment underway.
A portable ultraviolet steriliser, on the other hand, eliminated 73.5 per cent of the microbes after 10 minutes. “(These devices) only sterilise the surface of the area that touches the UV rays,” observed Lee.
Boiling the sponge for the same duration delivered the best result, slashing the count by 98.47 per cent. But she cautioned that boiling your sponge does not mean using the same one for a long time.
Repeated exposure to the heat may damage the sponge’s polymer structure, causing it to break down and become “very soft”. “It may not do the cleaning work it’s supposed to be doing,” she added.
Material matters too. Pacific Lab Services tested several types of scrubbing tools after five days of regular use and found that the cleanest was not a sponge at all — it was a dishwashing brush.
Not as many food particles lodge in its bristles as they do in sponges, observed project and lab manager Tan Li Mien. “So … less bacterial growth.”
Pacific Lab Services’ Tan Li Mien holding up the dishwashing brush.
A silicone sponge was the second cleanest, followed by an antimicrobial sponge. Despite its higher price and marketing claims, the antimicrobial sponge showed “quite a lot of bacteria”, Tan said.
The worst performer was one that claimed to be long-lasting, designed for extended use without replacement. It had almost 12 times as many colony-forming units than the antimicrobial sponge and more than the typical yellow and green sponge as well.
For Ser, she will still change her sponge weekly — but with a new kitchen routine.
“At the end of the day, I’ll be washing my sponge with hot water and … drying my sponge in an open space overnight, just to kill more bacteria,” she said.
Watch this episode of Talking Point here. The programme airs on Channel 5 every Thursday at 9.30pm.
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