it's an image much beloved of hollywood directors: the head lowered over a mirror, a crisp greenback tightly rolled and inserted in a nostril, then applied at the other end to a line of white powder.
researchers from the american chemical society in washington have discovered that the practice of consuming cocaine through rolled up paper money is far more than just a cinematic cliché. they found that in big cities in the us, up to 90% of the notes tested positive for traces of the drug.
in washington itself, the percentage of notes with cocaine residue reached 93%, a prevalence almost matched by other urban areas such as boston, detroit and baltimore.
though some of the contamination can be blamed on cocaine crystals being rubbed from one note onto others in bundles of currency, the researchers did find an apparent growth in the phenomenon. similar tests conducted two years ago found that only 67% of us banknotes had cocaine traces.
the study put that growth down to a probably increase in cocaine consumption in america, where there are thought to be as many as 6 million regular users of the drug.
for the first time, the researchers compared the results with tests on banknotes from other parts of the world. after the us and canada, brazil recorded almost as high a frequency of cocaine residue, at 80% of its paper money.
china (20%) and japan (16%) were notably lower on the scale.
any film directors hoping to be authentic in their portrayal of cocaine snorting should note that the researchers found that in the us the bills of choice of cocaine consumers were $5, $10, $20 and $50. both the modest dollar note, and the more elusive $100 note appear to be rarely deployed as an aid to nasal intoxication.
好莱坞导演都喜欢这样一个场景：一个人把头低到一张玻璃茶几上，卷紧一张挺括的美钞，然后把一段插入鼻孔，另一端则探到一线白色粉末里。
来自华盛顿美国化学协会（american chemical society）的研究员们发现，人们通过卷美钞吸食可卡因的做法绝不只在电影中出现。他们发现在美国的大城市里，多达90%的美钞被检测出有毒品的痕迹。
在华盛顿，沾染可卡因的美钞比例达到93%，而其它城区如波士顿、底特律和巴尔的摩大，也几乎与之并驾齐驱。
尽管造成污染的原因部分可以归咎于，可卡因晶体在成堆的现金里摩擦时，从一张钞票沾到了其他钞票上，研究人员确实发现了该现象的显著增长。而两年前进行的类似测试中，只在67%的美钞里找到可卡因的痕迹。
研究人员将这种增长归因于美国可卡因吸食者数量的增多，他们认为经常吸食毒品的美国人多达6百万。
研究人员首次把研究结果与世界其它地方进行比较，紧随美国和加拿大之后，巴西沾染过可卡因的纸币比例也高达80%。而中国（20%）和日本（16%）的比例则明显要小很多。
任何力求真实再现鼻吸可卡因场景的电影导演都应该注意了：研究人员发现，美国的瘾君子们会选择5美元、10美元、20美元和50美元面额的钞票购买毒品。而这里面最小面值的美钞（5美元），以及更少见的百元美钞似乎都很少被用作享受毒品的辅助手段。