The global hookah-smoking trend is so pervasive that in some nations’ towns, 70% of university students do it daily; small kids do it; parents and kids do it together. Hookah cafes range from Karachi to Kansas, Iran to Iowa.

The practice is escalating. The hookah has been around for 400 years. Yet among the 169 research papers on the topic listed with Pubmed, half were published since the start of 2012, 44 so far this year alone.

“The fact that parents and children smoke hookah together,” says Pradnya Kakodnar, a Patil Dental College and Hospital professor, describing what surprised her most during her 2013 study of rampant hookah use in Pune, India.

“Our 70% figure surprised me, for it is a concern and highlights the possible high addiction levels of users,” says Nicolette Roman, University of the Western Cape Senior Lecturer, referring to the part of her 2013 analysis finding that 70% of 389 students in a South African college smoke hookah daily.

Yet the most surprising part of her study, Roman says, was the discovery of “children’s exposure in the home … One of our South African studies indicates a small percentage of children younger than 10 years who smoke the hookah.”

An Addictive Behaviors study has called hookah/waterpipe smoking a “global epidemic.”

All this has occurred despite mounting evidence that hookah harms may be different from—but equal to/greater than—those of cigarette smoking. The most dramatic study was that of the World Health Organization (WHO), which found that smoke inhaled during an hour-long waterpipe session was the equivalent of 100 cigarettes.

But more studies are accumulating.

“It is scary how little has been done and how many people smoke a hookah regularly or even multiple times a day,” says Ryan Saadawi, a graduate student studying the subject with chemist Joseph Caruso of the University of Cincinnati (a hookah cafe hot spot.) (Saadawi reported on the work at the recent American Chemical Society (ACS) meeting).

The main quality distinguishing hookah from other tobacco trends is the degree to which people think it is unharmful. Aiding in this perception is the fact that the tobacco, or shisha, is generally mixed with kid-friendly ingredients, including molasses and honey, and given the flavors of bubble gum, apple, mint, cherry, chocolate, coconut, licorice, cappuccino and watermelon.

Its exotic nature is another draw for teens. The very names for hookah evoke mysterious foreign worlds: narghile, argileh (Jordan, Lebanon, Syria, Israel), shisha, borry, goza (Egypt, Saudi Arabia), shui yan dai (China) and hubble-bubble.

But with its spread to Western nations like the US—in particular, areas around US college campuses—more intensive study has begun, and the news is not good.

Saadawi reported at the ACS meeting that four metals—arsenic, lead, cadmium and chromium—are present in hookah tobacco, if less prevalently than in cigarettes. But other harmful substances are found at far higher levels, he and others have found.

In research published this year, the team of University of California, San Francisco research chemist Peyton Jacob found that two higher weight carcinogenic PAHs (polycyclic aromatic hydrocarbons), phenanthrene and pyrene, are higher in hookah than cigarette smoking. "Because higher molecular weight PAHs are generally the most carcinogenic (e.g., benzopyrene and benzanthracene), this trend suggests cancer risk from PAHs might be higher in water pipe smokers than in cigarette smokers,” reported Jacob’s team.

Ditto re: benzene, levels of which are “considerably higher” in hookahs than in cigarettes, and cause leukemias. his team noted. Ditto also re: carbon monoxide, levels of which are “much higher” in hookahs than cigarettes. Carbon monoxide is the gas people use to kill themselves with when they sit in garages and turn on the car.

Indeed, “If you go to hookah café without ventilation you will notice the carbon monoxide,” said the University of Cincinnati’s Traci Hanley at the ACS press conference, adding that her group is studying second-hand carbon monoxide poisoning via hookahs.

“Most surprising to me is the continuing appeal of tobacco products, even among well-educated young adults,” says Brown University Public Health professor Michael Carey. “Simple tricks, like using flavored tobacco or semi-exotic practices (a hookah pipe) coupled with the open-mindedness and curiosity of emerging adults lead to the initiation of a harmful, often addictive process that can have dramatic health consequences.”

Carey is coming out with a paper in November’s Addictive Behaviors showing that pre-college hookah use predicts cigarette smoking, and pre-college marijuana use predicts hookah smoking.

Estimates of lifetime hookah use among US college students range between 41 and 48 percent, according to the American Lung Association. In a recent survey of US 12^th graders, 17 percent reported hookah use in the past year.

Hookah “pens” have also become popular recently.