Money is genuinely filthy, but it’s not the dirtiest thing in the world. Kitchen sponges, toothbrush holders, and cell phones consistently carry higher bacterial loads than currency in comparative studies. That said, paper money is remarkably contaminated: 70% of banknotes sampled in one study carried more than 3,000 bacterial colonies per bill, with many too densely covered to even count. So while money doesn’t win the “dirtiest” title, it’s a serious contender.
What’s Actually Living on Your Cash
A global systematic review of currency contamination identified an astonishing range of organisms on paper money. Researchers found over 35 species of bacteria, more than 25 types of fungi, and roughly 20 parasitic organisms. The bacterial list includes well-known troublemakers like E. coli, Salmonella, Staphylococcus aureus (the species behind staph infections), and Pseudomonas aeruginosa, which can cause skin and wound infections. Fungi on banknotes include Aspergillus and Candida species, both of which can cause infections in people with weakened immune systems.
Perhaps more unsettling, researchers at Queen Mary University of London found that one in seven banknotes is contaminated with fecal organisms. Six percent of the notes they tested showed what they called “gross contamination,” meaning bacteria levels on par with a dirty toilet bowl. One in ten bank cards showed fecal contamination too, so going cashless doesn’t entirely solve the problem.
Money from certain environments is worse than others. Banknotes collected from fish markets showed colony counts above 3,000 in over 83% of samples. Coins fared somewhat better overall: about 77% of coin samples had fewer than 1,000 colonies, likely because of the metals they’re made from.
Why Paper Bills Are Worse Than Coins
The material money is made from matters enormously. Paper and cotton-blend banknotes are porous, providing tiny crevices where bacteria can lodge and moisture can linger. Coins, particularly those containing copper, have a built-in defense mechanism. Copper releases ions that generate reactive oxygen species, essentially unstable molecules that tear apart bacterial and viral membranes. This process destroys microbes on contact over time, which is why copper has been used as an antimicrobial surface for centuries.
Virus survival data tells a similar story. SARS-CoV-2 lasts about three hours on paper but can persist for up to seven days on plastic surfaces. Influenza survives six to eight hours on paper versus 24 to 48 hours on plastic and stainless steel. Banknotes fall somewhere in the middle of the durability scale, more hospitable to pathogens than copper or plain paper, but less so than plastic or glass. Polymer banknotes, which many countries now use, may actually harbor viruses slightly longer than traditional cotton-paper bills because of their smoother, less absorbent surface.
How Germs Actually Transfer From Money to You
Finding bacteria on a banknote is one thing. Getting sick from it is another. A detailed risk assessment of virus transmission through cash transactions found that the dose of pathogens you’d actually pick up is thousands of times lower than what you’d receive from direct exposure like a cough. When someone coughs on a banknote and hands it to you, the amount of virus that reaches a fingertip-sized area is about 400 times less than what was in the original cough. Transfer from the banknote to your finger reduces the count by another five to twenty times, depending on whether conditions are wet or dry. Then only about a third of what’s on your fingertip would transfer to your face if you touched it.
The researchers estimated that the risk of contracting COVID-19 from a single cash transaction was less than once per 107 years for an average person. Even cashiers handling money all day faced a risk of less than once per 21 months of working days. The takeaway: money carries germs, but the chain of events needed for those germs to actually infect you is long and inefficient.
What’s Dirtier Than Money
Several everyday objects consistently outperform currency in contamination studies. Kitchen sponges are the classic winner, harboring bacterial densities that can reach into the billions per cubic centimeter. Your phone screen, which you press against your face regularly, often carries more bacteria per square inch than a toilet seat. Cutting boards, dish towels, bathroom faucet handles, and computer keyboards all tend to surpass money in microbial load.
The reason money gets singled out is psychological as much as scientific. Cash passes through dozens or hundreds of hands, picking up skin cells, sweat, oils, and whatever those hands last touched. That journey feels uniquely gross. But objects that stay in warm, moist environments and rarely get cleaned, like that kitchen sponge sitting by your sink, are biologically far worse.
Practical Ways to Reduce the Risk
The single most effective thing you can do after handling cash is wash your hands before touching your face or food. This simple step breaks the transmission chain at its most vulnerable point. Hand sanitizer with at least 60% alcohol works as a backup when soap and water aren’t available.
If you work in food service or handle cash frequently, keeping hand-washing intervals short matters more than avoiding cash altogether. The contamination risk from money is real but manageable, and it’s no different in principle from the risk posed by touching door handles, shopping carts, or elevator buttons. Money is dirty, sometimes remarkably so, but the world is full of dirty surfaces. Your hands are the bridge between those surfaces and your body, and keeping that bridge clean is what actually protects you.