For a study that appears in the current issue of the journal Pediatrics, scientists in Montreal mailed questionnaires in 2007 and 2008 to 1,208 people ages 18 to 24 who had participated in an earlier study of nicotine use by teenagers. Three-quarters completed the questionnaires.
In the United States, studies of college students have estimated that 9 to 20 percent have used a hookah in the previous month.
The senior author of the paper, Jennifer O'Loughlin, a professor of epidemiology at the University of Montreal, said there were several widespread myths that water pipes are safer than cigarettes.
"One myth is that because the texture is smoother, it is less toxic, and the water filters out the toxins," O'Loughlin said. "That is not at all true."
In fact, she said, the pipes may expose smokers to higher amounts of nicotine and heavy metals than cigarettes.