Dirty money typically implies some illegal activity. But in this instance, it’s literally the gross situation going down in your wallet. Is there any truth to those urban legends about the unpleasant stuff hitching a ride on the backs of your Benjamins? Let’s just say we recommend carrying credit over cash.
Dolla Dolla Germ Ya’ll
Paper money does a lot of traveling from person to vending machine to grocery store to piggy bank and beyond. Along the way, these bills pick up a lot of hitchhikers. A 2017 study published in PLoS ONE highlights all the, uh, disturbing details.
The study, performed by New York University and IBM Almaden Research Center researchers, looked at $1 circulating around New York City in February (Winter) and June (Summer) 2013. The study identified more than 100 different strains of bacteria on the dollar bills, the most common being Propionibacterium acnes (a bacterium known to cause acne) and Streptococcus oralis (a common bacterium found in our mouths).
There’s a lot of non-human associated stuff crawling around on there too, though. The study also detected DNA from our pets, disease-causing viruses and bacteria, and Lactococcus lactis and Streptococcus thermophilus on the bills, microbes typically associated with dairy production and fermentation.
As for the urban legend stuff, yes, a significant percentage of paper currency also carry traces of drugs. In 1996, it was reported that cocaine was present on 79 percent of currency samples analyzed. Most had just a teeny tiny amount (0.1 micrograms), but still, you catch our drift. A 2001 study found that morphine, heroin, methamphetamine, and amphetamine can also be found on bills, though less commonly than cocaine.
This study found how money can have “molecular echoes” of human activity. Not unlike how strontium in your teeth can tell scientists where you’ve lived, ATMs can reveal differences in culture from different geographic regions. A 2016 study published in Applied and Environmental Science identified the “urban microbiome” found on ATM keypads from different New York City neighborhoods. By recovering traces of DNA from the keypads, researchers found that people in central Harlem ate more chicken than those in Flushing and Chinatown, who ate more species of bony fish and mollusks.
We’re not just trying to gross you out. As reported by The Washington Post, identifying foods that people eat or the drugs people use based on interactions with money might seem random and useless, but it’s not. Scientists can use this data to understand patterns of disease. The good news is that most of the microbes the researchers in New York identified do not cause disease. A 2002 study suggests that disease-causing strains of bacteria or virus could be passed along with our currency. Just wash your hands well and often, please.