"In April, a new study identified over a hundred different strains of bacteria on dollar bills circulating in New York City. Some of the most common bugs on our bills included Propionibacterium acnes, a bacteria known to cause acne, and Streptococcus oralis, a common bacteria found in our mouths.The research team, led by biologist Jane Carlton at New York University, also discovered traces of DNA from domestic animals and from specific bacteria that are associated only with certain foods.A similar study recovered traces of DNA on ATM keypads, reflecting the foods people ate in different neighborhoods.
People in central Harlem ate more domestic chicken than those in Flushing and Chinatown, who ate more species of bony fish and mollusks. The foods people ate transferred from fingers to touchscreens, where scientists could recover a bit of their most recent meals.
We don’t leave only food behind. Traces of cocaine can be found on almost 80 percent of dollar bills. Other drugs, including morphine, heroin, methamphetamine and amphetamine, can also be found on bills, though less commonly than cocaine."