TORONTO - Nearly nine out of 10 Canadian banknotes examined by a team of U.S. researchers contained trace amounts of cocaine.

In a study presented Sunday at the National Meeting of the American Chemical Society, researchers looked at banknotes from more than 30 cities in Canada, the U.S., Brazil, China, and Japan.

Twenty-seven Canadian bills, taken mostly from Toronto and the Sarnia, Ont., area, were analyzed, said lead researcher Yuegang Zuo, a chemistry and biochemistry professor at the University of Massachusetts Dartmouth.

Of the Canadian bills, 85 per cent were laced with cocaine. The amount of coke found on the banknotes ranged from 2.4 micrograms to upwards of 2,530 micrograms -- approximately 100 grains of sand.

The results in the U.S. were similar. The researchers examined 234 bills from 17 U.S. cities and found that nearly 90 per cent of the notes contained trace amounts of cocaine.

Scientists have long known that money can become contaminated with cocaine during drug deals or by snorting the drug through rolled bills.

Bills that are not involved in drug deals can also be contaminated as they are processed by banks.

Such studies can be useful for police, said Zuo, because they can help identify drug traffic patterns in a particular community.

But he also said an analysis of 27 Canadian banknotes is not enough to make sweeping generalizations about cocaine use in the country.

"It doesn't really represent the whole of Canadian currency," said Zuo.

"The number is too small. More substantive research is needed."

Law enforcement agencies might look to research like Zuo's to help boost the number of drug-related arrests, but that alone won't lower addiction rates, said University of Ottawa criminology professor Irvin Waller.

"The real issue is how much money you're putting into prevention," said Waller.

"Even if you know where (the cocaine) is flowing, this isn't a lot of help unless you're going to be putting money into reducing demand for it in that area."

The rates of North American bills laced with cocaine was significantly higher in Zuo's research than banknotes from China and Japan.

Of the 112 Chinese banknotes researchers analyzed, only one in five contained any sign of the drug. Only two of the 16 Japanese banknotes were contaminated with cocaine.

Despite the study's findings, Zuo said people shouldn't have any health or legal concerns about handling drug-tainted paper money.

In most of the notes examined, the amount of cocaine found was too small to interfere with drug tests or cause any health problems, he said.