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

Abstract

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 = 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.

Fate of pyrazines in the flavored liquids of e-cigarettes

“…AcP represented well the behavior of the pyrazines in the commercial samples since it was the most abundant in the tested liquids. We observed complete evaporation of AcP from the sample holder at 130 °C, which was considered a lower temperature than the reported temperatures in the vicinity of the ECIG heating element (Geiss et al 2016, Talih et al 2017). …”

“…PG and VG were quantified using a previously reported method (Talih et al 2017). In brief, 2 µL of liquid was dissolved in 1 mL of ethyl acetate and sonicated for 30 min.…”

Electronic cigarette user plasma nicotine concentration, puff topography, heart rate, and subjective effects: Influence of liquid nicotine concentration and user experience.

“…In light of results from the present study and other results (Wagener et al, 2017), policies aimed at limiting ECIG nicotine delivery to the user likely will need to account for more factors than liquid nicotine concentration alone: user behavior and device power are also relevant. A mathematical model is available that predicts the rate of ECIG nicotine emissions (e.g., nicotine flux; Shihadeh & Eissenberg, 2015) and it takes into account many factors, including liquid nicotine concentration, user behavior, and device power (Talih et al, 2017). Such models are potentially valuable regulatory tools.…”

“…These device components were selected after preliminary testing revealed that their nicotine emissions approached those of a tobacco cigarette under some conditions (see Talih et al, 2015; 2017). The cartomizer was pre-loaded with 1 ml of a flavored liquid (tobacco or menthol; chosen by participants at screening), that was comprised of 70% PG and 30% VG (AVAIL Vapor, Richmond, VA).…”

Assessing electronic cigarette effects and regulatory impact: Challenges with user self-reported device power

“…With regard to users, higher power devices may increase abuse liability and nicotine dependence as higher power devices produce more nicotine-containing aerosol for inhalation (e.g., Sleiman et al, 2016; Talih et al, 2017) and may also increase adverse health effects as the aerosol produced by these higher power devices also can be more toxicant-laden than low power devices (Gillman et al, 2016; El-Hellani et al, 2016). With regard to policymakers, the availability of higher power devices limits the impact of regulations regarding nicotine liquid concentration.…”