Prediction of potential passive exposure from commercial electronic nicotine delivery systems using exhaled breath analysis and computational fluid dynamic techniques.

Introduction:
This article presents a study that measures the exhaled breath concentrations of various constituents from users of electronic nicotine delivery systems (ENDS) and cigarettes. The study aims to use this data as input parameters to predict temporal and spatial concentrations in an environmental chamber, office, restaurant, and car using different ENDS use scenarios. The ultimate goal is to estimate potential exposure of non-users to exhaled ENDS constituents.

Key Points:

* The study measured exhaled breath concentrations of glycerin, propylene glycol, nicotine, benzoic acid, formaldehyde, acetaldehyde, acrolein, menthol, and carbon monoxide from use of eight different commercial ENDS devices and a non-menthol and menthol cigarette.
* The mean minimum and maximum per puff exhaled breath concentrations of glycerin, propylene glycol, nicotine, and menthol from use of the ENDS products were used as input parameters for the CFD model.
* The CFD model predicted temporal and spatial concentrations of the measured constituents in an environmental chamber, office, restaurant, and car using different ENDS use scenarios.
* The car with closed windows resulted in the greatest concentrations while opening the car windows produced the lowest concentrations.
* The CFD predicted average maximum glycerin and propylene glycol concentration ranged from 0.25 to 1068 µg m−3 and 1.5 pg m−3 to 13.56 µg m−3, respectively.
* The CFD predicted maximum concentration of nicotine and menthol ranged from 0.16 pg m−3 to 4.02 µg m−3 and 0.068 pg m−3 to 2.43 µg m−3, respectively.
* There was better agreement for CFD-predicted nicotine concentrations than glycerin and propylene glycol with published reports.
* Maximum measured nicotine levels from environmental tobacco smoke in offices, restaurants, and cars exceeded the maximum average CFD predictions by 7-97 times.
* For all the measured exhaled breath constituents and CFD predicted constituents, except for propylene glycol and glycerin, concentrations were less from use of ENDS products compared to combustible cigarettes.

Main Message:
The study demonstrates that the exhaled breath of ENDS users is the source of the constituents measured in all the various environmental studies used to estimate potential exposure of non-users to exhaled ENDS aerosol. The use of exhaled breath data and computational fluid dynamic (CFD) modeling techniques can provide predictions of individual constituent concentrations in any indoor environment, which is a more efficient methodology than conducting actual exposure studies in each indoor environment. The study also highlights the importance of comparing CFD predictions with measured concentrations to account for experimental and computational variables. Overall, the study provides valuable insights into estimating potential exposure to exhaled ENDS constituents and emphasizes the need for further research in this area.

Oldham MJ, Bailey PC, Castro N, Lang q, Salehi a, Rostami aa. Prediction of potential passive exposure from commercial electronic nicotine delivery systems using exhaled breath analysis and computational fluid dynamic techniques. Journal of breath research. 2021;15(4). doi:10.1088/1752-7163/ac2884