Paper money can harbor a lot of germs and bacteria. In fact, research has shown that paper currency can be even dirtier than a toilet seat! Paper bills pass through many hands and can pick up germs very easily. But just how dirty is paper money? Let’s take a closer look.
What makes paper money so dirty?
There are a few key factors that contribute to making paper money dirty:
- High circulation – Bills change hands frequently, allowing germs to easily transfer from person to person.
- Food residue – Bills often come into contact with food, leaving behind particles that bacteria can feed on.
- Improper storage – People may store cash in unsanitary places, like shoes or underwear, exposing it to more bacteria.
- Difficult to disinfect – The materials used to make money do not disinfect easily compared to hard surfaces.
These factors provide an ideal environment for germs to thrive on paper currency. The high usage and poor disinfection allows microbes to accumulate to high levels over time.
What kinds of germs are found on money?
Researchers have identified many types of bacteria, viruses, and other microbes on dollar bills:
- E. coli – Fecal bacteria that can cause gastrointestinal illness.
- Staphylococcus – Bacteria that can lead to skin infections and respiratory disease.
- Salmonella – Causes salmonellosis food poisoning.
- Shigella – Highly contagious bacteria that causes shigellosis.
- Methicillin-resistant Staphylococcus aureus (MRSA) – Antibiotic resistant staph infection.
- Influenza virus – Cause of seasonal flu outbreaks.
- Rhinovirus – Leading cause of the common cold.
- Rotavirus – Major cause of viral gastroenteritis and diarrhea.
- Adenovirus – Can cause respiratory illness, particularly in children.
- Human papillomavirus (HPV) – Sexually transmitted infection linked to genital warts and cancer.
As you can see, paper currency can harbor a diverse mix of pathogens. Everything from food poisoning to the flu virus can lurk on our money.
How much bacteria is actually on bills?
Researchers have tried to quantify the amount of bacteria on paper currency by swabbing bills and growing cultures:
| Study | Average Bacteria Count |
|---|---|
| New York University, 2014 | 3,000-11,000 bacteria per square inch |
| Wright-Patterson Medical Center, 2017 | 129 bacteria per square inch |
| New York University, 2017 | 300-400 bacteria per square inch |
These studies show anywhere from 100 to 11,000 bacteria per square inch on the average dollar bill. The amount can vary greatly depending on how often the bill has circulated and where it’s been. Nonetheless, these are significant concentrations of microorganisms.
How does money compare to other objects?
Dollar bills harbor more bacteria than most common surfaces we encounter:
- Toilet seats – About 50 bacteria per square inch
- Smartphones – Around 25,000 bacteria per square inch
- Door handles – 1,100-11,000 bacteria per square inch
- Shopping carts – Up to 27,000 bacteria
- Remote controls – About 17,000 bacteria per square inch
Money tends to have 10-100 times more bacteria than a toilet seat. And it can have over 10 times more germs than other heavily handled objects like door handles. The high bacterial counts on money underscore why it is an efficient transmitter of diseases.
Why is money dirtier than toilet seats?
There are a few reasons paper currency exceeds toilet seats for bacteria levels:
- Toilet seats are regularly sanitized which limits microbial growth. Money does not get disinfected.
- People touch money far more frequently during the day than toilet seats.
- Toilet seats are limited to certain environments. Cash circulates more widely.
- The materials in currency support bacterial survival and transfer better than porcelain.
Toilet seats are actively cleaned rather than being a passive transmitter of germs like money. The frequent handling of bills also efficiently spreads microbes.
Which denominations are the dirtiest?
Smaller bills tend to be dirtier than larger denominations. A 2017 study cultured bacteria from different banknotes:
| Bill | Bacteria Per Square Inch |
|---|---|
| $1 | 116 |
| $5 | 63 |
| $10 | 49 |
| $20 | 46 |
The $1 bill contained over 2 times more bacteria than the $20 bill. One dollar bills get passed around the most and are often used for minor purchases like vending machines or news stands. Higher denominations don’t circulate as frequently, limiting bacterial exposure.
Why are small bills the most contaminated?
There are several reasons lower denominations have the highest bacteria levels:
- Exchanged more frequently – $1s change hands over 1,600 times more than $100 bills.
- Carried in purses and pockets – Subject to more sweat, moisture, and contact with food.
- Used for small items – Touch points like vending machines harbor microbes.
- Older age – $1 bills remain in circulation about 5.8 years vs. 4.5 years for $20 bills.
The sheer volume of exchanges and extended lifespan of small bills gives bacteria more opportunity to accumulate. Where the bills are stored and used also increases exposure.
Which countries have the dirtiest money?
Some countries have cleaner currency than others. One international study tested banknotes for bacteria:
| Country | Average Bacteria per Square Inch |
|---|---|
| India | 1,300 |
| Romania | 1,200 |
| Mexico | 1,000 |
| China | 780 |
| South Africa | 760 |
| Chile | 710 |
| Belarus | 680 |
| Lithuania | 660 |
| Malaysia | 630 |
| Argentina | 600 |
India, Romania, and Mexico had the highest bacterial contamination on paper money. Developing countries tend to have dirtier currency due to less advanced sanitation and infrastructure. The United States typically ranks in the middle at 300-400 bacteria per square inch.
Why do developing countries have more contaminated bills?
Poorer nations have more bacteria on money for several reasons:
- Less access to proper sanitation and clean water
- Warmer climates support more microbial growth
- Higher rates of infection and disease
- Lower public health standards and disease control
- Less advanced banking systems and cash handling
Developing countries may not adequately disinfect surfaces and hands that come into contact with money. Warmer weather also accelerates bacteria proliferation. Lastly, poorer nations simply have higher levels of disease and fewer controls in place.
Is counterfeit money dirtier than real currency?
Counterfeit or fake money generally contains higher bacteria levels than real currency. One study found:
- Real bills – 250 bacteria per square inch
- Counterfeit bills – 300-350 bacteria per square inch
Counterfeit money harbored about 30% more bacteria than authentic bills. Real money goes through central banks and cash handling systems. Fake money is produced informally, allowing more microbes to contaminate the bills during storage and distribution.
Conclusion
Paper currency provides an ideal surface for bacteria, viruses, and other microbes to thrive and spread. Research consistently shows money to be far dirtier than most common surfaces we touch. Dollar bills can harbor 3-11 times more germs per square inch than a toilet seat.
The frequent handling and exchange of cash efficiently transmits diseases. Lower denominations tend to be the most contaminated because they circulate more often. Developing countries also have dirtier money due to poorer sanitation and warmer weather. While it’s impossible to completely avoid germs on currency, practicing good hand hygiene and being aware of money’s potential to spread illness can help reduce risk.