How Dirty Is Your Money?

How Dirty Is Your Money?

Find out which germs—and illegal drugs—reside on your cash.

We think about money constantly—one survey showed Americans think about their finances even more than sex—but have you ever really thought about what’s actually on your cash?  

Money hosts pathogens and poop
Many studies have shown that money is home to a wide range of bacteria—about 3,000 types of bacteria, in fact—and many common viruses, including influenza. One report from the Southern Medical Journal revealed that 94 percent of dollar bills tested hosted pathogens like staphylococcus, the cause of staph infections, and streptococcus, the bacteria responsible for strep throat and scarlet fever.

Think switching to plastic will help avoid bugs? Unfortunately, your credit and debit cards aren’t so sanitary either; one study found that 1 in 10 bankcards had traces of fecal matter and bacteria like E. coli and another discovered that 50 percent of credit cards in their sample tested positive for methicillin-resistant Staphylococcus aureus, more commonly known as MRSA.

If you’re otherwise healthy, it’s unlikely that the germs on money will actually make you sick, but it’s a good idea to wash your hands after handling cash. 

Most US currency is contaminated with cocaine
An analysis of paper money from 17 US cities showed up to 90 percent of bills tested were contaminated with cocaine. If you have a $5 bill, $10 bill or $20 bill in your wallet, it’s more likely to have trace amounts of cocaine; $1 bills and $100 bills averaged less contamination.

The study also examined banknotes from China, Japan, Brazil and Canada. While China and Japan’s currencies had lower levels of cocaine contamination, 80 percent of Brazilian money and 85 percent of Canadian money had been contaminated.

It’s unclear whether or not most contamination comes from drug use or from contaminated bills mingling with uncontaminated bills, but researchers believe bills with larger amounts of cocaine were used to consume cocaine or exchanged in a drug deal.

Soiled money can influence your spending
Do you have any old, tattered bills in your wallet? One study discovered that you’re more likely to reach for those worn out bills when making a purchase. Why? We want to ditch ugly, dirty banknotes, in favor of crisp, clean currency you’d be proud to spend in front of your friends. This suggests the physical appearance of money can seriously influence your finances—we spend more when using worn bills and less when using crisp ones.

The Federal Reserve uses the “soil content” of money to determine whether or not a banknote is fit to remain in circulation. Based on soil content and general wear, about 95 percent of the money printed today is produced solely to replace worn, old bills.

Medically reviewed in August 2018.

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