it would seem from a new analysis of 234 banknotes from 18 U.S. cities that found cocaine on 90 percent of the bills tested.
What might be more surprising is the fact that the percentage of contaminated bills seems to be rising; just two years ago, Zuo did a similar study that found cocaine on only 67 percent of banknotes in Massachusetts. "It is too early to draw a conclusion about why," Zuo says. "The economic downturn may partly contribute to the jump.
Levels of cocaine ranged from .006 micrograms to more than 1,240 micrograms—the equivalent of 50 grains of sand—on U.S. bills, and $5, $10 and $20 bills on average carried more contamination than $1 or $100 bills.
Cocaine can end up on US currency through direct contact with contaminated bills, as well as through the handling of bills by individuals who have recently handled drugs or drug paraphernalia.
It is unlikely that handling cocaine-contaminated currency would cause a positive drug test. The amount of cocaine present on bills is typically very small and may not be enough to trigger a positive result.
Cocaine residue can stay on US currency for varying lengths of time, depending on factors such as the amount of cocaine present, the type of surface the bill is on, and environmental conditions. In some cases, cocaine residue can remain on bills for several years.
There is a very low risk of health effects from handling US currency tainted with cocaine. The amount of cocaine present on bills is typically not enough to cause any significant health effects, especially with short-term exposure.
The presence of cocaine on US currency does not affect its monetary value. However, some businesses and individuals may refuse to accept or handle bills that are visibly contaminated with drugs.