Toxicant content, physical properties and biological activity of waterpipe tobacco smoke and its tobacco-free alternatives

Abstract

Objectives: Waterpipe smoking using sweetened, flavoured tobacco products has become a widespread global phenomenon. In this paper, we review chemical, physical and biological properties of waterpipe smoke.

Data sources: Peer-reviewed publications indexed in major databases between 1991 and 2014. Search keywords included a combination of: waterpipe, narghile, hookah, shisha along with names of chemical compounds and classes of compounds, in addition to terms commonly used in cellular biology and aerosol sizing.

Study selection: The search was limited to articles published in English which reported novel data on waterpipe tobacco smoke (WTS) toxicant content, biological activity or particle size and which met various criteria for analytical rigour including: method specificity and selectivity, precision, accuracy and recovery, linearity, range, and stability.

Data extraction: Multiple researchers reviewed the reports and collectively agreed on which data were pertinent for inclusion.

Data synthesis: Waterpipe smoke contains significant concentrations of toxicants thought to cause dependence, heart disease, lung disease and cancer in cigarette smokers, and includes 27 known or suspected carcinogens. Waterpipe smoke is a respirable aerosol that induces cellular responses associated with pulmonary and arterial diseases. Except nicotine, smoke generated using tobacco-free preparations marketed for 'health conscious' users contains the same or greater doses of toxicants, with the same cellular effects as conventional products. Toxicant yield data from the analytical laboratory are consistent with studies of exposure biomarkers in waterpipe users.

Conclusions: A sufficient evidence base exists to support public health interventions that highlight the fact that WTS presents a serious inhalation hazard.

Keywords: Carcinogens; Non-cigarette tobacco products; Toxicology.

Figure 1

The head, body, bowl and hose are the primary components that make up a narghile waterpipe. To draw smoke through the water bubbler, the user must generate a vacuum sufficient to overcome the several centimetre water column residing above the submerged body outlet. The static head of the water is the primary flow resistance in the system felt by the smoker; adding or reducing the water level in the bowl modulates the drag experienced by the user. Some fraction of the drawn smoke volume (roughly one-third) remains in the head space of the water bubbler between puffs, and is displaced by fresh smoke in subsequent puffs. Flow passages are located at the base of the clay head to allow the smoke to pass into the central conduit of the body that leads to the water bowl. Because of the long path traversed by the smoke as it passes from the head, through the body, to the water bowl, and through the hose to the smoker, there are ample opportunities for gas and particulate phase deposition, diffusion, and evaporation/condensation processes to occur, as well as particle–particle coagulation. Adapted from ref. .