In the largest study of its kind, researchers analyzed bank notes from countries around the world and reported that cocaine is present in up to 85 per cent of Canadian notes, and 90 per cent of notes from the United States. Of the samples taken from 30 cities in five countries—Brazil, Canada, China, Japan and the United States—the U.S. and Canada had the highest rate of contamination. Contaminated notes from Canada had a range of 2.4 micrograms to over 2,530 micrograms of coke per bank note. China and Japan had the lowest levels of contamination, between 12 and 20 per cent. The authors say the study suggests that cocaine abuse is still rampant and may even be on the rise in some cities.