Your wallet is likely carrying traces of cocaine and bacteria

Wealth & Business · Published 18 October 2026 Swipe more like this →

In short: It is a startling reality of modern circulation: most banknotes are tainted with illicit drugs. From Los Angeles to London, studies show that cocaine is remarkably persistent on paper currency, spreading through financial institutions via simple proximity and mechanical sorting.

The prevalence of drug traces on paper money is well-documented across several continents. In the United States, studies have found cocaine on as much as 92% of randomly collected one-dollar bills, with some estimates for the Chicago suburbs reaching 80% or even as high as 94%. In London, a 1999 study revealed that out of 500 notes tested, only four were free of cocaine. While cocaine is the most common contaminant due to its stability, other substances like heroin, methamphetamine, and PCP have also been detected. Interestingly, researchers note that while the presence of drugs is high, it is virtually impossible for cocaine to rub off on your hands simply by handling the bills.

The mechanism of contamination is often a matter of passive transfer rather than direct use. While some notes may be used directly for snorting drugs, much of the spread occurs in enclosed environments like banks. When contaminated notes are stacked or processed through counting machines, the substance moves to clean currency. This phenomenon has even led to legal complexities; in the U.S., the presence of drugs on a note is often too low for a criminal prosecution but high enough to trigger a reaction from drug-sniffing dogs, leading to legal disputes over what constitutes 'unusual' levels of contamination.

Beyond narcotics, banknotes act as reservoirs for various microbes. Research in New York City has identified human skin and oral bacteria, such as Staphylococcus epidermidis, on paper money. Even more surprising is the presence of bacteria typically associated with dairy production, like Lactococcus lactis. There are also significant public health concerns regarding bloodborne pathogens. The Hepatitis C Trust has warned that sharing notes used in drug use could facilitate the transmission of Hepatitis C, a virus that can remain dormant for decades and lead to chronic liver disease.

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