Chemical Constituents and Particle Size Distribution of Mainstream Emission from Electronic Waterpipe

Introduction An electronic waterpipe (electronic hookah) uses an electronic heating element to promote the vaporization and aerosolization of an e-liquid in a waterpipe. There is little or no published information characterizing the toxicant levels or particle size distributions (PSDs) of electronic waterpipe mainstream emission. Methods Controlled laboratory experiments were performed to evaluate electronic waterpipe mainstream emission for 40 test conditions: 10 e-liquid products × 2 power settings × 2 puffing topographies. Data were collected for amounts of three volatile toxicants and selected semi-volatile compounds, mass of total particulate matter, and PSD within the size range of 5-1000 nm. Results Amounts of the volatile toxicants acetaldehyde, acrolein, and benzene measured in mainstream emission were 33-505 μg/session, 27-415 μg/session, and 0.69-2.44 μg/session, respectively. The amounts of acetaldehyde and acrolein, when reported in units of μg/puff, are generally similar to some literature-reported amounts in e-cigarette mainstream emission and tobacco waterpipe smoke. A bimodal or trimodal PSD was typically observed, and substantial concentrations of nanoparticles were detected. The amounts (in μg/puff) of the volatile toxicants and several quantitative measures of PSD were significantly affected by power setting and puffing topography. Conclusions Given the hazards of acetaldehyde and acrolein and the distinctive toxicological profile of nanoparticles, electronic waterpipe use may present significant toxicity concerns. Operation of an electronic waterpipe is a complex process in which physics, fluid dynamics, and chemistry interact to yield mainstream emission for which the composition is sensitive to changes from various sources. Implications This publication, to our knowledge, is the first to report the amounts of toxicants and PSDs in electronic waterpipe mainstream emission. The results reported herein suggest that there may be significant toxicity concerns associated with electronic waterpipe use as indicated by the levels of volatile toxicants and the presence of nanoparticles in electronic waterpipe mainstream emission. This knowledge is valuable to support the research community and tobacco regulatory agencies in understanding the impact that electronic waterpipe use may have on public health.