If the coronavirus pandemic has taught us anything, it's the importance of keeping our hands clean. While we know to sanitise our hands after going to the toilet, we probably don't do the same after paying for our food.
But if you don't already do this you might want to start – because new research has revealed that cash is actually pretty filthy.
The study, by Merchant Machine analysed the movement of cash in the UK to work out the number and types of bacteria that can be found on individual banknotes.
And the results are shocking.
Despite studies revealing that cash usage in the UK has decreased drastically by 22% over the last ten years, and many businesses going cashless for safety reasons during the pandemic, it seems we're still at risk of handling germ-riddled notes.
We already knew germs spread relatively easily through touch, which means we can pick them up from touching door handles and shaking hands (hence the switch from hand shaking to elbow tapping during the coronavirus pandemic).
But turns out we can also pick up germs when we handle money.
The findings reveal that the humble £5 is the grubbiest UK banknote, with an average of 50.9 transactions, resulting in almost 153,000 bacteria in its 5 years of circulation.
Some of the nasties gathered on this type of note include Bacillus Pumilus, Coliforms, Listeria and Yeast.
Coliform can be found in human and animal waste and can cause symptoms including diarrhoea, stomach cramps and vomiting.
Listeria can be also found in human and animal faeces (grim) and in soil.
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The average £10 banknote is spent around 10.5 times in the course of its 5 year lifespan, gathering an average of 330 potentially harmful bacteria, including Listeria and Staphylococcus Aureus.
In a particularly concerning twist, the latter is known to be antibiotic resistant and it is considered extremely dangerous by the World Health Organisation (WHO). It can potentially cause skin infections and affect blood and intestinal organs.
Due to smaller usage, the £50 note is actually considered to be the ‘cleanest’ UK banknote, gathering on average only 120 potentially harmful bacteria, including Bacillus Pumillus, Micrococcus and Staphylococcus Aureus.
But Bacillus Pumilus can be particularly dangerous for children and can cause skin infections. Micrococcus is a type of bacteria typically found in soil and water, and people with a weaker immune system are more likely to be impacted by it.
“We all touch money on a day-to-day basis without much thought as to where it has been or who has handled it before," says Dr Richard Hastings, expert in microbiology and healthcare regulatory and technical manager for Hycolin. "However, money can carry viruses and bacteria, so it is important to protect yourself from spreading germs, especially during a pandemic."
Dr Hastings says money acts as a fomite, which means it is an inanimate vehicle that enables pathogens to spread.
"Therefore, if you handle money and then touch someone’s hand, you are able to pass on any bacteria or viruses that may be present," he continues.
"The simplest way to prevent this from happening is to remember to wash your hands thoroughly with soap and use hand sanitiser after touching any coins or notes when out and about. Temporarily wearing gloves when using money could also help to prevent infections spreading.”
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The good news is that previous research has found that plastic bank notes - like the new £5 and £10 - are far cleaner than cotton notes.
They are three times more hygienic, and bacteria is far less likely to survive on them. So in the long run, our notes could end up being marginally less gross.
But in the meantime, it's probably a good idea to wash or sanitise your hands after handling cash - bringing a whole new meaning to money laundering.