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Bacterial Bills

Not only are there traces of cocaine lining your dollar bills, there is also a thriving microbial community. By analyzing genetic material found on dollar bills, researchers from New York University's Dirty Money Project have found some 3,000 types of bacteria on them, the Wall Street Journal reports.

The most common microbe they found is the one that causes acne, but the researchers also identified ones that linked to food poisoning, gastric ulcers, pneumonia, and staph infections as well as ones harboring antibiotic resistance genes. The Journal notes that the researchers were only able to identify the source of some 20 percent of the non-human DNA they collected.

"We're not trying to be fear mongers, or suggest that everyone goes out and microwave their money," Jane Carlton, director of genome sequencing at NYU's Center for Genomics and Systems Biology, tells NPR's Shots blog. "But I must admit that some of the $1 bills in New York City are really nasty."

Bills in the US are made of a blend of cotton and linen, though other countries like Canada and Bhutan have begun printing money on more durable flexible plastic polymer films. According to the Journal, one recent study found that fewer microbes lived on such plastic bills than on cotton-based ones, while another study found microbes could live longer on plastic polymer bills.

"Until the ideal material gets figured out, the best protection against money's invisible inhabitants is also the simplest one: Wash your hands after handling cash," NPR adds.