U.S. Currency Contaminated with Cocaine

The vast majority of U.S. paper money in circulation contains traces of cocaine, a new study finds.

CNN reported Aug. 18 that researchers found that 90 percent of $1, $5, $10, $20 and $50 bills tested had detectable cocaine residue. Bills from major cities were more likely to test positive than those from smaller cities.

Some of the bills had only tiny traces of drugs, suggesting that they may have simply come into contact with tainted bills in currency-counting machines. And $1 bills were the least likely to test positive for cocaine. “Probably $1 is a little too less to purchase cocaine,” said researcher Yuegang Zuo of the University of Massachusetts at Dartmouth. “I don’t know exactly [why]. It’s an educated guess.”

Zuo’s research was unveiled at a recent meeting of the American Chemical Society. A similar study found nearly identical results a decade ago, and researcher Adam Negrusz of the University of Chicago said that while the contaminated bills don’t pose a health risk, they can create other types of problems, such as false positives on drug tests.

“Imagine a bank teller who’s working with cash-counting machine in the basement of the bank,” Negrusz said. “Many of those bills, over 90 percent, are contaminated with cocaine. There is cocaine dust around the machines. These bank tellers breathe in cocaine. Cocaine gets into system, and you can test positive for cocaine … That’s what’s behind this whole thing that triggered testing money for drugs.”