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

Introduction:
This text summarizes a scientific study examining the chemical constituents and particle size distribution of the mainstream emission from electronic waterpipes (also known as e-hookahs or electronic hookahs). The study aimed to provide new knowledge to support the research community and tobacco regulatory agencies in understanding the impact that electronic waterpipe use may have on public health.

Key Points:

* The study used controlled laboratory experiments to evaluate electronic waterpipe mainstream emission for 40 test conditions, including 10 e-liquid products, two power settings, and two puffing topographies.
* Data were collected for amounts of three volatile toxicants (acetaldehyde, acrolein, and benzene) and selected semi-volatile compounds, mass of total particulate matter, and particle size distributions (PSDs) within the size range of 5--1000 nm.
* Amounts of the volatile toxicants in mainstream emission ranged from 33--505 µg/session for acetaldehyde, 27--415 µg/session for acrolein, and 0.69--2.44 µg/session for benzene.
* A bimodal or trimodal PSD was typically observed, and substantial concentrations of nanoparticles were detected.
* 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.
* The amounts (in µg/puff) of the volatile toxicants and several quantitative measures of PSD were significantly affected by power setting and puffing topography.

Main Message:
The study highlights that electronic waterpipe use may present significant toxicity concerns due to the hazards of acetaldehyde and acrolein and the distinctive toxicological profile of nanoparticles. The 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. This knowledge is valuable for tobacco regulatory agencies to consider when evaluating the potential public health impact of electronic waterpipe use.

Theodore P Klupinski, Anna Adetona, Alexander Ivanov, Aaron Richardson, Erich D Strozier, Laura L S Aume, Hani Karam, Stephanie D Makselan, Martha McCauley, Larry Mullins, Billie Stiffler, Eric A Lucas, Hyoshin Kim, Chemical Constituents and Particle Size Distribution of Mainstream Emission From Electronic Waterpipe, Nicotine & Tobacco Research, Volume 27, Issue 7, July 2025, Pages 1265–1273, https://doi.org/10.1093/ntr/ntaf028