If an item is handled by the public, whether it's a library book, a subway pole, or an ATM, you can count on it being filthy. One of the worst offenders is something most people carry around wherever they go: money. As TIME reports, a new study confirms that paper money is a magnet for germs and other microorganisms.

For their paper, which appears in the journal PLOS One, researchers swabbed dozens of $1 bills collected from New York City banks over the course of 2013. The results showed microbes from numerous sources living within the fibers. Most came from the human body, like skin bacteria, oral bacteria, and even vaginal bacteria. But non-human DNA was also prevalent. In the summer, researchers were most likely to find traces from pets like dogs and horses, while microbes from indoor fungi were more common in the winter. Skin break out lately? The bacteria to blame for acne were the most common microorganisms detected.

That list alone is enough to make you feel squeamish when leafing through your wallet, but it doesn't end there. American paper currency is 75 percent cotton and 25 percent linen; this composition makes it a cozy environment for other microorganisms like viruses. According to SmartMoney, the flu can survive on paper money for more than 10 days under the right conditions. E. coli and salmonella have also been detected on paper bills.

While these facts make a good case for washing your hands after each transaction, there's no reason to make the full switch to plastic. The same properties that make money such a good home for bacteria also make it hard to spread those germs to people. When microbes settle into the woven material of a dollar, they tend to stay there, even when you take it out and pass it to someone else. And if some microbes do rub off on you, your skin does a great job of keeping them from getting inside your body where they can do real harm. But you should still remember to use hand sanitizer before eating that burger you just paid for.

Unfortunately, objects touched by strangers aren't the only germ-infested environments to be aware of. Here are some of the dirtiest surfaces lurking in your home.

[h/t TIME]