Up to 90 percent of paper money in the United States contains traces of cocaine, according to a study by the American Chemical Society released Monday.
Scientests analyzed currency in more than 30 cities in five countries, and the US and Canada posted the highest levels of contamination, according to the study. China and Japan posted the lowest levels of contamination, between 12 and 20 percent.
On a global level, cocaine traces jumped almost 20 percent compared to a similar study conducted two years ago, said Yuegang Zuo of the University of Massachusetts in Dartmouth.
"I'm not sure why we've seen this apparent increase, but it could be related to the economic downturn, with stressed people turning to cocaine," Zuo said in a press release.
The scientists studied 234 bills from the US, which came from 17 cities. Money from larger cities, such as Boston and Washington, D.C., contained the most cocaine.
Although a high percentage of the money was contaminated, the amount was not significant enough to raise any health concerns, Zuo said.
"For the most part, you can't get high by sniffing a regular banknote, unless it was used directly in drug uptake or during a drug exchange," he said.