What The Germs On Dollar Bills Can Tell Scientists About Human Activity

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Dirty money isn't just dirty — it can divulge an interesting lot about human activity. According to a team of biologists from New York University, you can learn a lot about human behavior and movement by studying the microbes found on paper currency in New York City.

On Monday, CNN reported on the findings, highlighting the presence of a variety of bacteria on paper money. In turn, these organisms create "molecular echoes" that can be used to track and trace human movements and activities. In the official NYU report, "Molecular echoes" refers to the microbial interaction between humans and their physical environments. For instance, the everyday exchange of microbial content between your skin and an ATM keypad could produce a molecular echo.

The paper, titled Filthy Lucre, is a metagenomics study. In simpler terms, it's dedicated to understanding genetic material found and recovered from humans' physical environments. By studying the surface of $1 bills in New York City, the team of biologists found interesting things present on the external layer of hard cash circulating in the Big Apple.

If you are a germaphobe, you might not want to know the nitty gritty of undoubtedly icky findings — for example, two commonly-occurring bacteria on the dollar bills were the acne-inducing Propionibacterium acnes and mouth bacteria like Streptococcus oralis.

The research isn't exactly new. Metagenomic studies centering on money and our human hands goes back to the late 1800s. The primary reason for wanting to understand this interaction was to comprehend and improve the hygienic conditions in handling and holding money.

By understanding the human-microbe exchange, researchers have attempted to develop cleaning mechanisms for money before people hold cash in their hands. A cleaning method like that — otherwise known as "fluid cleaning" — would involve exposing banknotes to temperature-specific carbon dioxide and removing excess oil and dirt from the notes. As research indicates, it's a tricky process because you don't want to harm the delicate security elements in the note that protect from counterfeiting.

Metagenomic studies like the one from NYU are helpful on several frontiers. On an immediate level, the study can help Americans better understand exposure to disease-enabling bacteria passed by way of dollar notes. Although the paper does not say that cash is responsible for spreading disease (it's very rare for it to happen), it can still explain how human-microbe interfaces provide environments for bacteria to stay alive. It can also assist in tracking drug use; elements of cocaine, morphine, and heroin — among other substances — are frequently found on dollar notes.

Your money might be dirty, but there's no reason to panic: these microbes are not fatal. In fact, they live just about everywhere. As long as you keep your hands clean and don't carry cash in your mouth, you don't have to worry.