Though often perceived as harmless - and even considered suitable for children by some - water pipe smoking may be associated with significant harms, according to a new study published in the journal Cancer Epidemiology, Biomarkers & Prevention.

"Water pipes" typically consist of a head that is connected to a water jar, with an attached hose and mouthpiece. Tobacco and a moist fruit preparation are placed below burning charcoal in the head of the contraption.

When a smoker inhales through the mouthpiece, the air from the burning charcoal is pulled through the layer of tobacco and then through the water - where it is cooled - as bubbles, before being breathed in through the hose and mouthpiece.

This is a traditional smoking method going back centuries, known across various cultures as hookah, shisha, sheesha, hubble-dubble and many other names.

Studies report that in some regions, such as the US, Europe and the eastern Mediterranean, there has been a significant recent increase in water pipe smoking, particularly among the young. Research suggests that as many as 40% of college students in the US report ever having used a water pipe, with 20% reporting having smoked using a water pipe in the past 30 days.

New study challenges perception of water pipe smoking as 'safe'

Despite a popular opinion that water pipe smoking is less harmful than cigarette smoking, water pipe users are exposed to significant levels of carbon monoxide, nicotine, tobacco-specific nitrosamines (TSNA), carcinogenic polycyclic aromatic hydrocarbons and volatile aldehydes over the duration of the smoking session.

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As many as 40% of US college students report ever having used a water pipe, with 20% reporting having smoked using a water pipe in the past 30 days.

The new study, funded by the National Institutes of Health and the California Tobacco-related Disease Research Program, used biomarkers to investigate the extent to which smokers are exposed to nicotine, TSNAs and volatile organic compounds over the course of one evening's smoking at a hookah bar.

The team recruited 55 healthy and experienced water pipe smokers for the study, who were aged 18-48. The participants provided a urine sample before smoking water pipes at a hookah bar of their choice in the San Francisco Bay area. They were also asked to refrain from any form of smoking for a week before the experiment.

Both immediately after the visit and the morning after smoking, the participants again provided the researchers with urine samples. They also filled in questionnaires providing details on total time spent smoking, number of bowls smoked and number of shared users.

On average, the people in the study spent 74 minutes smoking and smoked an average of 0.6 bowls of water pipe tobacco each.

Elevated levels of nicotine, cotinine and 4-(methylnitrosamino)-1-(3-pyr- idyl)-1-butanol were found in the participants' urine immediately after smoking. In the next-day urine sample, these substances also remained in significant levels.

The researchers say the average increase in nicotine levels was comparable to the increase in nicotine a person would get after smoking at least one cigarette.

What policy implications might this research have?

Lead author Gideon St. Helen, PhD - from the Center for Tobacco Control Research and Education at the University of California, San Francisco - told Medical News Today that the study has clear policy implications:

"One public health concern is the use of water pipes among adolescents and young adults and whether it leads to nicotine dependence. This is an area that warrants further research, as the answer is not clear. However, our study showed substantial intake of nicotine in users of water pipes in the hookah bar setting."

Dr. St. Helen said that previous studies suggest that the average increase in nicotine levels the team measured in these water pipe users were high enough to cause physiological changes in the brain that can sustain nicotine addiction.

"Also important is the exposure to cancer-causing compounds in water pipe smoke such as benzene, which is known to cause leukemia, the most common cancer in children and teens," said Dr. Helen, who claims to have seen entire families - including young children - smoking water pipes in the belief that they are "totally safe."

"Thus, restrictions on sale to minors and banning the use of water pipes by minors in public places or commercial establishments are sensible public health policies," he said.

Although the study did not assess cancer risk from water pipe smoking, Dr. St. Helen told us that the team "believe that smoking water pipes increases the user's risk for cancer, depending on the frequency of use and lifetime smoking duration."

"Our study provides important exposure data that can help epidemiologists determine the magnitude of the cancer risk," he concluded.