Transport phenomena governing nicotine emissions from electronic cigarettes: Model formulation and experimental investigation

Project description

Electronic cigarettes (ECIGs) electrically heat and aerosolize a liquid-containing propylene glycol
(PG), vegetable glycerin (VG), flavorants, water, and nicotine. ECIG effects and proposed methods to
regulate them are controversial. One regulatory focal point involves nicotine emissions. We describe
a mathematical model that predicts ECIG nicotine emissions. The model computes the vaporization
rate of individual species by numerically solving the unsteady species and energy conservation
equations. To validate model predictions, yields of nicotine, total particulate matter, PG, and VG
were measured while manipulating puff topography, electrical power, and liquid composition
across 100 conditions. Nicotine flux, the rate at which nicotine is emitted per unit time, was the
primary outcome. Across conditions, the measured and computed nicotine flux were highly
correlated (r D 0.85, p < .0001). As predicted, device power, nicotine concentration, PG/VG ratio,
and puff duration influenced nicotine flux (p < .05), while water content and puff velocity did not.
Additional empirical investigation revealed that PG/VG liquids act as ideal solutions, that liquid
vaporization accounts for more than 95% of ECIG aerosol mass emissions, and that as device power
increases the aerosol composition shifts towards the less volatile components of the parent liquid.
To the extent that ECIG regulations focus on nicotine emissions, mathematical models like this one
can be used to predict ECIG nicotine emissions and to test the effects of proposed regulation of
factors that influence nicotine flux.


First name Last name Gender Rank Affiliated Institution Country
Dean Alan Shihadeh Male American University of Beirut Lebanon

Bio: Dr. Shihadeh earned his undergraduate degree from the University of Texas at Austin and his doctorate in sciences in mechanical engineering from the Massachusetts Institute of Technology (MIT) in the field of combustion in 1998. He taught at Birzeit University before joining AUB as an assistant professor of Mechanical Engineering.
At AUB, he conducted a systematic study of emissions from waterpipe tobacco smoking, the first in a series of ground-breaking studies on the chemistry, human behavior, and health effects of the practice. Evidence produced by what became the AUB Aerosol Research Laboratory (ARL) – now a leading center that develops and exports scientific instruments to research laboratories in North America, Europe, and the Middle East – led the World Health Organization (WHO) to issue its first International Advisory warning in 2005, compelling regional and international governments to include waterpipes in tobacco control efforts.
Dr. Shihadeh serves as an advisor to the Food and Drug Administration (FDA), a scientific expert to the World Health Organization (WHO), and a Project Director and Executive Leadership Committee member of the Center for the Study of Tobacco Products at Virginia Commonwealth University. He is a member of the Air Quality Research Unit, an AUB-Saint Joseph University collaboration, and a member of the Editorial Advisory Board of the American Chemical Society’s Chemical Research in Toxicology journal. He co-directs the Collaborative for Inhaled and Atmospheric Aerosols and the Tobacco Control Research Group at AUB, and sits on the Tobacco-Free AUB 2018 Task Force.



Scientific field

Engineering and technology

Start Year


End Year


Funding Agency

Funding Agency Funding Agency Type Country of Funding Agency
National Institute on Drug Abuse in the U.S. Department of Health and Human Services Governmental Organization United States of America

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