Dirty Money: Cash Has More Disease-Causing Bacteria Than You Think


Dirty money often refers to money obtained illegally, but it turns out that it can be taken far more literally. According to a new study published in Frontiers in Microbiology, cash can become home to harmful bacteria and spread disease quickly.

Courtesy: Andy/Flickr

Due to the exchange of so many hands, it is often said that paper money and coins should be handled carefully, and washing one’s hands after handling money is recommended, especially for food service employees. However, these aren’t the only people who should be mindful of what they touch after using cash.

A group of researchers from Hong Kong exposed the true depth of dirtiness, finding cold hard cash to be an effective medium for transmitting harmful, disease-causing bacteria.

“In short, banknotes act as a medium ‘absorbing’ bacteria from other environments and the potential pathogens live quite well on the banknote surface,” said Jun Li co-author of the study and a researcher from the University of Hong Kong.

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To gather evidence, these researchers collected 20 dollar Hong Kong banknotes from 12 different hospitals and three metro stations and scraped them for bacteria. They found that not only was the cash very much a carrier of bacteria, but the bacteria they found contained especially dangerous strains such as E. coli and the cholera-causing bacteria, V. cholerae.

20 Dollar Hong Kong Banknote. Courtesy: Banknote World

Compared with people’s hand, the banknotes had a much larger variety of bacteria accumulated; they contained even more bacteria than drinking water, the air from a metro station, and marine sediment. Additionally, the bacteria found on the banknotes was more resistant to antibiotics than bacteria found in any of the other tested sources.

This is not the first time that money has been found to contain traces of bacteria — and more. In one study in Scientific American in 1998, even small amounts of cocaine and fecal matter were discovered on paper bills. In their estimation, smaller bills were more likely to be contaminated. Ones, fives, and tens were the dirtiest, while larger denominations saw less handling in general and therefore remained cleaner.

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The Hong Kong researchers believe that the first step to solving this matter is to promote a cash-free society, using only plastic money to conduct transactions.

Li told reporters, “The most important recommendation we could raise is that before a cashless society develops, the banks and government should pay extra attention to the hygiene problem of the currency, which is still frequently used in our daily life. We recommend some routine disinfection of the currency from the bank, some public service ads reminding people to pay attention to wash the hands after touching currencies and the promotion of more electronic payment service, like mobile payment. We particularly would like to see the politicians and policy-makers inspired by this study.”