Almost all euro banknotes circulating in Germany contain traces of cocaine, German researchers say.
Some cocaine users snort the drug through rolled bank notes
Cocaine users commonly use a rolled-up banknote to inhale the drug through the nose, and experts say such notes can contaminate the cash system in cash counting machines in banks.
"Nine out of 10 banknotes show clearly measurable amounts of cocaine," Professor Fritz Soergel of the Institute for Biomedical and Pharmaceutical Research in Nuremberg was quoted as saying by Reuters news agency.
However, Professor Soergel - who tested some 600 notes - said his study was only a "social detector" and could not provide conclusive evidence of the drug usage in Germany and other euro zone countries.
The concentrations of cocaine on Spanish euro notes were almost a hundred times that of what we recorded in Germany
The professor has been studying banknotes on highly sensitive drug-testing equipment for years.
Soon after the euro went into circulation in January 2002, his team found that two out 70 notes had traces of cocaine.
The latest figures were based on the study carried out in August last year.
Professor Soergel said there was a clear correlation between the findings and levels of recorded cocaine use in the 12 countries of the euro zone.
"Studies have shown that the amount of cocaine found on banknotes in countries where there is less cocaine usage, such as France, Finland and Greece, is much lower than in countries where it is more widespread," he said.
Professor Soergel said that his team was "almost knocked flat" by results of yet another recent study in Barcelona.
"The concentrations of cocaine on Spanish euro notes were almost a hundred times that of what we recorded in Germany," he said.