Electronic cigarette effectiveness and abuse liability: predicting and regulating nicotine flux

Estimating human pharmacokinetic parameters forelectronic nicotine delivery system products from chemical analyses of their aerosols

The ability of Electronic Nicotine Delivery Systems (ENDS) to deliver nicotine is central to their function to substitute for cigarettes, allowing people who smoke to switch away from smoking, thus reducing their exposure to harmful chemicals in cigarette smoke. The nicotine concentration in ENDS e-liquid has proved to be a poor predictor of nicotine uptake in users. Using meta-analytic methods to analyze 12 pharmacokinetic studies of nicotine-salt closed-system ENDS, this paper examines whether the mass of nicotine/puff of aerosol can predict Cmax in pharmacokinetic studies. Cmax values were available for 38 products, in 58 use conditions (including both controlled [3 s] and ad libitum puffing), comprising 1769 participant observations. Nicotine/puff data reflected chemical analyses of aerosol obtained under nonintense (3 s) or intense (6 s) machine puffing. Meta-regression analyses (weighted by reliability of Cmax estimate) assessed the relationship of nicotine/puff to Cmax. In some models, empirical data were used to impute the variation in Cmax or the nicotine/puff value under intense puffing. In simple linear models, Cmax was significantly associated with nicotine/puff under all combinations of intense/nonintense and controlled/ad-libitum conditions, with R2 values of 0.71-0.77. More complex models based on quadratic effects or log[nicotine/puff] did not generally improve upon more parsimonious linear models. Application of the model illustrates the divergence between nicotine concentration in e-liquids and expected Cmax when other ENDS parameters vary. The meta-analytic model may have utility in settings where clinical pharmacokinetic data are not available, including product development.

Factors Associated With Successful E-Cigarette Cessation Among a Convenience Sample of Adult Users

Background: A growing body of literature suggests that many people who use e-cigarettes become dependent and have difficulty quitting. Most people who use e-cigarettes have interest in quitting, yet there is currently a lack of evidence to inform interventions for e-cigarette cessation. Objective: The purpose of this study was to identify factors associated with successful e-cigarette quit attempts among a large sample of people who use e-cigarettes. Methods: Participants (n=586) were people who use e-cigarettes who reported at least one lifetime attempt to quit their e-cigarette use. Adjusted logistic regression models were performed to examine differences in e-cigarette use characteristics and quit methods between people who currently use e-cigarettes and who quit e-cigarettes. Results: Most participants were people who currently use e-cigarettes and only 27.5% reported successfully quitting. Most participants (90.6%) used e-cigarettes that contained nicotine, and over half (54.0%) used closed-system e-cigarette devices with replaceable pre-filled pods or cartridges. The quit method most commonly used overall (63.1%) and for people who quit e-cigarettes (70.8%) was cold turkey. Past 30-day cigarette use and past 30-day other tobacco use was significantly associated with reduced odds of quitting, and there were no e-cigarette characteristics significantly associated with successful cessation. Nicotine replacement therapy was the only e-cigarette cessation method that was significantly associated with increased odds of quitting after adjusting for past 30-day cigarette and other tobacco use. Conclusions: These results suggests that cigarette use, other tobacco use, and quit method used may significantly influence the likelihood of e-cigarette cessation. Future research is needed to determine the effectiveness of interventions for e-cigarette cessation using nicotine replacement therapy.

Transitions in device and liquid characteristic groupings among US adults frequently using electronic nicotine delivery systems (ENDS) over three timepoints, 2020-2021

INTRODUCTION

Electronic nicotine delivery system (ENDS) and liquid characteristics affect nicotine and toxicant exposure and use behaviors. Little is known about how adults who frequently use ENDS transition between ENDS device/liquid groupings.

METHODS

A total of 379 US adults (≥21 years) using ENDS frequently (≥5 days/week) self-reported and uploaded photos of their most used ENDS device and liquid in three waves of online surveys (May 2020 - November 2021). Device/liquid grouping was defined by device (i.e. disposable/refillable tank/refillable pod or cartridge/disposable pod or cartridge, adjustable/no adjustable settings) and liquid (i.e. salt/freebase) characteristics. Participants using the same grouping across waves were considered stable users.

RESULTS

The most prevalent wave (W) 1 grouping was tank (freebase, adjustable settings; 36.8%). From W1 to W3, the number of disposable device (salt, no adjustable settings) users increased 156.4% and the number of disposable pod/cartridge (salt, no adjustable settings) users decreased 15.2%. In W2 and W3, compared to stable users, participants using tank (freebase, adjustable settings) in W1 and another grouping in W2 and/or W3 reported significantly higher nicotine concentrations (mg/mL) (W2: 15.1 vs 5.5, p<0.001; W3: 22.9 vs 5.6, p<0.001) and lower device power (watt) (W2: 46.8 vs 58.7, p=0.02; W3: 34.0 vs 57.2, p<0.001).

CONCLUSIONS

Over a 1.5-year period, a rapid growth in disposable device (salt, no adjustable settings) use and a decrease in disposable pod/cartridge (salt, no adjustable settings) use were observed. Participants who transitioned from tank (freebase, adjustable settings) to other groupings were more likely to increase liquid nicotine concentration and reduce device power compared to stable users.

Nicotine flux as a powerful tool for regulating nicotine delivery from e-cigarettes: Protocol of two complimentary randomized crossover clinical trials

INTRODUCTION

Electronic cigarette (EC) use has increased rapidly in the last decade, especially among youth. Regulating nicotine delivery from ECs could help curb youth uptake and leverage EC use in harm reduction yet is complicated by varying device and liquid variables that affect nicotine delivery. Nicotine flux, the nicotine emission rate, is a parameter that incorporates these variables and focuses on the performance rather than the design of an EC. Nicotine flux therefore could be a powerful regulatory tool if it is shown empirically to predict nicotine delivery and subjective effects related to dependence.

METHODS AND ANALYSIS

This project consists of two complementary clinical trials. In Trial I, we will examine the relationship between nicotine flux and the rate and dose of nicotine delivery from ECs, hence, impacting abuse liability. It will also examine the extent to which this relationship is mediated by nicotine form (i.e., freebase versus protonated). At Yale School of Medicine (YSM), study participants will puff EC devices under conditions that differ by flux and form, while arterial blood is sampled in high time resolution. In Trial II, we will assess the relationship between nicotine flux, form, and subjective effects. At the American University of Beirut (AUB), participants will use EC devices with varying nicotine fluxes and forms, while dependency measures, such as the urge to use ECs, nicotine craving, and withdrawal symptoms, will be assessed. We will also monitor puffing intensity and real-time exposure to toxicants.

ETHICS AND DISSEMINATION

The protocol of Trial I and Trial II was approved by YSM and AUB IRBs, respectively. We will disseminate study results through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION

NCT05706701 for Trial I and NCT05430334 for Trial II.

Bigger, stronger and cheaper: growth in e-cigarette market driven by disposable devices with more e-liquid, higher nicotine concentration and declining prices

OBJECTIVE

Given the evolving changes in the disposable e-cigarette market, we explore patterns of sales in the USA by e-liquid volume capacity, nicotine strength and real sales-weighted average prices by both e-cigarette unit and volume of e-liquid.

METHODOLOGY

We used NielsenIQ retail scanner data from January 2017 to September 2022 to examine changes over time for average product volume capacity in millilitres, nicotine strength (%) and both sales-weighted average price per disposable unit and per millilitre of e-liquid for each 4-week period.

RESULTS

Among disposable e-cigarettes sold between January 2017 and September 2022, average volume capacity increased 518% from 1.1 mL to 5.7 mL and average nicotine strength increased 294% from 1.7% to 5%. Sales-weighted average price per disposable unit and millilitres of e-liquid both remained relatively constant until January 2020. From January 2020 through September 2022, average unit prices increased 165.7% from US$8.49 to US$14.07, while the average price of 1 mL of e-liquid decreased 69.2% from US$7.96 to US$2.45.

CONCLUSIONS

The current regulatory regime around e-cigarettes has resulted in disposable e-cigarette manufacturers providing consumers with bigger, cheaper disposable e-cigarettes that come in increasingly higher nicotine strengths. Tobacco policy recommendations such as restricting e-liquid capacity and minimum price laws as well as regulations on product characteristics that affect nicotine emissions and delivery such as nicotine strength, nicotine output, device power, and puff duration should be considered in regulating the e-cigarette market.

The Substitution of Fifty Percent of Combustible Tobacco Smoke Exposure With Either Electronic Cigarettes or Heated tobacco Products Did Not Attenuate Acute Lung Injury in an Animal Model

BACKGROUND

To reduce the harmful health effects of combustible cigarette smoke (CS), some (CS) users attempt to substitute CS with electronic cigarettes (ECIG) and/or heated tobacco products (HTP). In this animal study, we evaluated the acute effects of substituting CS consumption with ECIG or HTP thus mimicking the dual users' approach, on the lungs of a mouse model.

METHODS

C57BL/6 mice were divided into Control, ECIG, HTP, CS, ECIG + CS, HTP + CS, and HTP + ECIG groups. Animals were exposed for 3 hours in AM and PM sessions to either air, CS, ECIG, or HTP for seven days. Lung injury was assessed by: wet to dry (W/D) ratio, albumin concentration in bronchoalveolar lavage fluid, expression of IL-1β, IL-6, and TNF-α, histopathology examination, reactive oxygen species (ROS) production, and assessment of cellular apoptosis.

RESULTS

W/D ratio was significantly increased in mice exposed to CS only. Albumin leak and expression of IL-1β, IL-6, and TNF-a were elevated in CS, ECIG + CS, and HTP + CS. Histological examination revealed significant inflammatory cells infiltration, as well as collagen deposit in CS, ECIG + CS, HTP + CS. ROS production was significantly increased in CS, ECIG + CS, HTP + CS. Finally, cell death was also significantly increased in CS, ECIG + CS, and HTP + CS.

CONCLUSION

In this animal model, substituting 50% of daily CS exposure by either ECIG or HTP exposure did not result in significant attenuation of acute lung injury.

Appeal of e-cigarette flavors: Differences between never and ever use of combustible cigarettes

BACKGROUND

Characterizing the appeal of flavored e-cigarette solutions by tobacco product use status can inform regulations to reduce vaping in those who never smoked without discouraging adopting e-cigarettes as a quit-smoking aid.

METHODS

Adults aged 21+ who currently use tobacco products (N = 119) self-administered standardized puffs of eight non-tobacco flavored and two tobacco-flavored e-cigarette solutions using a pod-style device. Participants rated appeal (0-100 scale) following each administration. Mean differences in flavor appeal ratings were compared between four groups: people who never smoked/currently vape, formerly smoked/currently vape, currently smoke/currently vape, and currently smoke/do not vape (with interest in vaping).

RESULTS

The Global Flavor (all non-tobacco vs. tobacco)×Group interaction (p = .028) revealed higher appeal for non-tobacco vs. tobacco flavors in adults who never smoked/currently vape (B[95 %CI] = 13.6[4.1-23.1]), formerly smoked/currently vape (B[95 %CI] = 11.6[4.2-18.9]), and currently smoke/currently vape (B[95 %CI] = 9.3[2.5-11.6]), but not adults who currently smoke/never vaped (B[95 %CI] = -0.1[-5.1 to 4.9]). In flavor-specific analyses, adults who never smoked/currently vape rated strawberry (p = .022), peppermint (p = .028), and menthol (p = .028) more appealing than tobacco flavors. Among adults who formerly smoked/currently vape, strawberry (p < .001), peppermint (p = .009), and vanilla (p = .009), were more appealing than tobacco. Adults who currently smoked/currently vape rated peppermint (p = .022) and vanilla (p = .009) as more appealing than tobacco. No non-tobacco flavors were more appealing than tobacco in adults who currently smoke/never vaped.

CONCLUSIONS

E-cigarette sales restrictions on non-tobacco flavors, including menthol, may eliminate products preferred by adults who vape, including those who never smoked, without discouraging adults who currently smoke and never vaped from trying e-cigarettes.

Interactive effects of protonated nicotine concentration and device power on ENDS nicotine delivery, puff topography, and subjective effects

Electronic nicotine delivery systems (ENDSs) produce an aerosol by heating a liquid that often contains nicotine. The nicotine can be protonated that may make the aerosol easier to inhale than freebase nicotine. This study's purpose is to determine, in cigarette smokers and ENDS users, the effects of three concentrations of protonated nicotine aerosolized at two different power settings. Forty-five participants (22 cigarette smokers and 23 ENDS users) completed some or all of six sessions that varied by liquid nicotine concentration (10, 15, or 30 mg/ml protonated nicotine) and device power (15 or 30 W). Participants took 10 puffs from each product and then used each product for 90 min ad libitum. Plasma nicotine concentration, subjective effects, and puff topography were measured. Results showed increases in plasma nicotine concentration in all conditions, with greater plasma nicotine increases in higher watt, higher nicotine concentration conditions, as well as greater nicotine delivery for ENDS users compared to cigarette smokers. For puff topography, puff duration and volume decreased as nicotine concentration and power increased, and ENDS users took longer and larger puffs than cigarette smokers. Participants rated the higher watt, higher nicotine concentration conditions as harsher and with more throat hit. Overall, these results suggest that device characteristics and liquid constituents interact to influence users' plasma nicotine delivery and should be considered together when regulating ENDS. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Electronic Cigarette Nicotine Flux, Nicotine Yield, and Particulate Matter Emissions: Impact of Device and Liquid Heterogeneity

INTRODUCTION

Electronic cigarettes (ECIGs) heat a nicotine-containing liquid to produce an inhalable aerosol. ECIG power (wattage) and liquid nicotine concentration are two factors that predict nicotine emission rate ("flux"). These factors can vary greatly across devices and users.

AIMS AND METHODS

The purpose of this study was to examine ECIG device and liquid heterogeneity in "real world" settings and the association with predicted nicotine flux, nicotine yield, and total particulate matter (TPM) emissions. Past 30-day ECIG users (n = 84; mean age = 23.8 years [SD = 9.6]) reported device and liquid characteristics. Device power was measured via multimeter, device display screens, or obtained via labeling. Liquid nicotine concentration was obtained via labeling or through chemical analysis. Predicted nicotine flux, nicotine yield, and TPM associated with 10 4-second puffs were calculated for participants' primary devices.

RESULTS

Participants' primary devices were box mods (42.9%), disposable vapes (20.2%), and pod mods (36.9%). Most participants (65.5%) reported not knowing their primary device wattage. Rebuildable/box mods had the greatest power range (11.1-120.0 W); pod mod power also varied considerably (4.1-21.7 W). Unlike device wattage, most participants (95.2%) reported knowing their liquid nicotine concentration, which ranged from 3.0 to 86.9 mg/ml (M = 36.0, SD = 29.3). Predicted nicotine flux varied greatly across products (range =12.0-160.1 μg/s, M = 85.6 μg/s, SD = 34.3). Box mods had the greatest variability in wattage and predicted nicotine flux, nicotine yield, and TPM yield.

CONCLUSIONS

ECIG device and liquid heterogeneity influence nicotine and other toxicant emissions. Better measurement of ECIG device and liquid characteristics is needed to understand nicotine and toxicant emissions and to inform regulatory policy.

IMPLICATIONS

ECIG device and liquid heterogeneity cause great variability in nicotine flux and toxicants emitted. These data demonstrate the need to examine device and liquid characteristics to develop empirically informed, health-promoting regulatory policies. Policies may include setting product standards such that ECIG products cannot (1) have nicotine fluxes much greater than that of a cigarette to decrease the risk of dependence, (2) have nicotine fluxes that are very low and thus would have minimal appeal to cigarette smokers and may serve as starter products for youth or nontobacco users, and (3) emit large amounts of particulate matter and other toxicants.

Predictors of electronic cigarette dependence among non-smoking electronic cigarette users: User behavior and device characteristics

INTRODUCTION

ECIGs differ in their ability to deliver nicotine to the user and, consequently, they may differ in their ability to produce dependence. This study examined individual device characteristics, device type, and user behaviors as predictors of ECIG dependence in a sample of never-smoking ECIG users.

METHODS

Participants (N = 134) completed an online survey that assessed demographics, ECIG use behavior, and ECIG dependence as measured via the Penn State Electronic Nicotine Dependence Index (PSECDI) and E-cigarette Dependence Scale (EDS-4). Participants uploaded a picture of their personal ECIG device/liquid, which was coded by raters to identify product features. Multivariable linear regressions examined device characteristics (e.g., adjustable power, nicotine concentration) and device type (e.g., vape pen, mod, pod, modern disposable) as predictors of dependence controlling for demographics and user behaviors (e.g., ECIG use duration and frequency, other tobacco use).

RESULTS

Longer durations of ECIG use and more use days/week were associated significantly with higher PSECDI (β's = 0.91 and 1.90, respectively; p's < 0.01) and EDS-4 scores (β's = 0.16 and 0.28, respectively; p's < 0.01). Higher nicotine concentrations were associated with higher PSECDI scores only (β = 0.07, p =.011). Dependence scores did not differ as a function of ECIG device types after controlling for covariates.

CONCLUSIONS

ECIG dependence was observed among the never-smoking ECIG users in this sample, regardless of their ECIG device/liquid features. Findings suggest that regulatory efforts aimed at reducing the dependence potential of ECIGs in never smokers should focus on overall nicotine emissions rather than product features.

Development of pulsed intravenous nicotine infusions as a model for inhaled nicotine in humans

RATIONALE

Although nicotine from cigarettes is delivered in puff-sized amounts, most preclinical and human intravenous (IV) nicotine studies have used bolus or continuous infusions.

OBJECTIVES

To determine the feasibility of a pulsed-nicotine infusion model in smokers.

METHODS

Following overnight abstinence, 12 adult smokers underwent 5 laboratory sessions. Using a crossover design, in each session, participants were assigned to 1 of 5 conditions: (1) high/fast: 1.0 mg nicotine delivered over 5 pulsed-infusions, then 15 saline infusions; (2) high/slow: 1.0 mg nicotine delivered over 20 pulsed-infusions; (3) low/fast: 0.2 mg nicotine delivered over 5 pulsed-infusions, then 15 saline infusions; (4) low/slow: 0.2 mg nicotine delivered over 20 pulsed-infusions; and (5) placebo: Saline delivered over 20 pulsed-infusions. Subjective drug effects, urges to smoke, nicotine withdrawal, and cognitive performance were measured in each session.

RESULTS

Both the high/fast and high/slow conditions were associated with greater "head rush" and "high" (p < 0.05). The high/fast condition also provided greater suppression of urges to smoke and nicotine withdrawal (p < 0.05), indexed by the Questionnaire of Urges to Smoke-Brief, and the Minnesota Nicotine Withdrawal Scale, respectively. The high/fast and high/slow conditions produced greater increases in heart rate (p < 0.01) than saline. Finally, there were no main effects of dosing conditions on cognitive performance, indexed by the continuous performance test.

CONCLUSIONS

These findings demonstrate the feasibility of pulsed-nicotine infusions to model nicotine delivery by smoking. This model could inform future studies testing novel smoking cessation therapies and tobacco regulatory studies testing the impact of nicotine reduction approaches.

Novel Nicotine Concentration Labels Improve Adolescents' and Young Adults' Understanding of the Nicotine Strength of Electronic Nicotine Delivery System Products

INTRODUCTION

E-cigarette liquid nicotine concentrations typically are labeled as mg/mL or percent, which poorly convey nicotine strength to users. We evaluated whether four novel nicotine concentration labels better convey information about nicotine strength and addictiveness.

METHODS

Adolescents and young adults (N = 826) completed an online survey in 2020. Participants rated nicotine concentrations (3, 6, 18, 30, 40, and 50 mg/mL) from "no nicotine" to "very high nicotine" communicated using current market labels (mg/mL, percent) and four new labels (text-based, caution sign-shaped, horizonal stoplight, vertical thermometer) which used color, symbols, and verbal strength descriptors. Participants reported on perceived addictiveness for all labels viewed and rank-ordered labels on perceived ability to convey information accurately.

RESULTS

Participants ranked the vertical (77%) and horizontal (70%) labels in first or second place and mg/mL (59.1%) and percent (47.2%) in last or second-to-last place. All new labels conveyed nicotine strength more accurately than did market labels (M[SD] correct of 6: percent = 1.50[1.08]; mg/mL = 2.14[1.52]; caution = 5.23[1.37]; vertical thermometer = 5.28[1.51]; text = 5.33[1.36]; horizontal stoplight = 5.47[1.14]), with the horizontal label also outperforming the thermometer and caution labels. Underestimating nicotine strength was uncommon among all new labels (4.7-6.8%). The new labels also were associated with increased perceived addictiveness at higher concentrations (30, 40, and 50 mg/mL), although the thermometer label underperformed the others. When considering perceived nicotine strength, rates of strength underestimates, perceived addictiveness, and rank ordering, the horizontal stoplight label performed best.

CONCLUSIONS

Novel labeling could improve understanding of nicotine strength and e-cigarette-related risk.

IMPLICATIONS

Extending prior research showing that adolescents and young adults who use Electronic Nicotine Delivery Systems (ENDS) have difficulty understanding nicotine concentrations labeled using mg/mL and percent nicotine, the current study demonstrates that novel nicotine concentration labels can improve understanding of nicotine strength and influence perceptions of addictiveness among young ENDS users. While four novel labels were tested, each outperforming current market labeling, the novel label that resembles a horizontal stoplight performed best. The study provides proof-of-concept that creating an easy-to-understand nicotine concentration label is possible and that new labeling better conveys information about nicotine strength and addictiveness.

Impact of delivery rate on the acute response to intravenous nicotine: A human laboratory study with implications for regulatory science

Faster delivery rate enhances the abuse potential of drugs of abuse, yet systematic studies on the impact of delivery rate on the acute effects of nicotine in humans are lacking. Using an intravenous (IV) nicotine infusion procedure that allows precise control of rate of delivery, we examined the impact of nicotine delivery rate on the positive subjective drug effects, smoking urges, withdrawal, heart rate, blood pressure and attention function in smokers. Twenty-four male and female (ages 21-35) dependent smokers attended five experimental sessions, following overnight abstinence from smoking. Using a crossover design, participants attended five sessions, where they were assigned to a random sequence of saline infusion or 1 mg nicotine delivered over 1, 2.5, 5 or 10 min at rates of 1, 0.4, 0.2 or 0.1 mg/min, respectively. The positive subjective effects of nicotine were most robust under the two faster delivery rate conditions, 1- and 0.4-mg nicotine/min. In contrast, all nicotine delivery rates were equally more effective than saline in alleviating urges to smoke. Likewise, nicotine-induced heart rate increases did not vary with the rate of nicotine delivery. Lastly, the cognitive enhancing effects of nicotine were observed only under the two slowest delivery rate conditions-0.1- and 0.2-mg nicotine/min. Collectively, these findings support the critical role of delivery rate in optimizing nicotine's abuse potential versus potential therapeutic effects and have timely implications for developing novel therapeutics for nicotine dependence, as well as for tobacco regulatory science.

Comparison of nicotine emissions rate, 'nicotine flux', from heated, electronic and combustible tobacco products: data, trends and recommendations for regulation

INTRODUCTION

Tobacco smoking is a major cause of disease and premature death worldwide. While nicotine is recognised as the main addictive component in tobacco smoke, the total nicotine amount emitted (nicotine yield) and the rate of nicotine emission per second ('nicotine flux') contribute to the abuse liability of a given product. These variables can be regulated for public health ends and conveniently so for electronic cigarettes or electronic nicotine delivery systems (ENDS).

METHODS

In this study we computed nicotine flux from previously reported values of yield and puff topography for a wide range of tobacco products.

RESULTS

We found that nicotine flux varied widely across tobacco products, from less than 0.1 µg/s to more than 100 µg/s, and that since 2015 the upper limit of the ENDS nicotine flux range has risen significantly and is now approaching that of combustible cigarettes. We also found that products that differ in nicotine flux may exhibit similar nicotine yields due to differences in user puffing behavior. Nicotine flux is a tool that can be used to regulate nicotine emissions of tobacco products, including ENDS.

E-cigarette device and liquid characteristics and E-cigarette dependence: A pilot study of pod-based and disposable E-cigarette users

BACKGROUND

E-cigarette device and liquid characteristics, such as electrical power output and liquid nicotine concentration, determine the rate at which nicotine is emitted from the e-cigarette (i.e., nicotine flux), and thus are likely to influence user nicotine dependence. We hypothesize that nicotine flux would be associated with the E-cigarette Dependence Scale (EDS) among pod-based and disposable e-cigarette products.

METHODS

Data were obtained from online panel participants between 18 and 65 years of age, who had indicated that they were either former or current e-cigarette users and resided within the United States (N = 1036). To be included in these analyses, participants had to provide information regarding device type (pod-based or disposable), power (watts), and nicotine concentration (mg/mL), from which we could determine nicotine flux (µg/s) (N = 666). To assess the relationship between nicotine flux and EDS, a series of multivariable linear regressions were conducted. Each model was separated by device type and adjusted for by age and past 30-day e-cigarette use.

RESULTS

Greater nicotine flux was associated with higher EDS scores among pod-based e-cigarette users (beta = 0.19, SE = 0.09, p-value = 0.043), but not users of disposable e-cigarettes. Neither power nor nicotine concentration were associated with EDS scores among users of either e-cigarette device type.

CONCLUSION

Results support the hypothesis that nicotine flux is positively associated with nicotine dependence in a sample of current users of pod-based and disposable e-cigarettes.

Effect of Electronic Nicotine Delivery Systems on Cigarette Abstinence in Smokers with no Plans to Quit: Exploratory Analysis of a Randomized Placebo-Controlled Trial

INTRODUCTION

The extent to which use of electronic nicotine delivery systems (ENDS) for smoking reduction leads to cigarette abstinence in smokers with no plans to quit smoking is unclear. This exploratory analysis examined the effects of ENDS delivering different amounts of nicotine on cigarette abstinence up to 24-week follow-up, in comparison to placebo or a behavioral substitute.

METHODS

This four-arm parallel-group, randomized, placebo-controlled trial took place at two academic medical centers in USA (Penn State Hershey and Virginia Commonwealth University). Participants were current adult smokers (N=520) interested in reducing but not planning to quit. They received brief advice and were randomized to one of four 24-week conditions, receiving either an eGo-style ENDS paired with 0, 8 or 36 mg/ml nicotine liquid (double-blind) or a cigarette-shaped tube, as a cigarette substitute (CS). Self-reported daily cigarette consumption and exhaled carbon monoxide (CO) were measured at all study visits. Outcomes included intent-to-treat, self-reported 7-day cigarette abstinence, biochemically confirmed by exhaled CO at 24 weeks after randomization.

RESULTS

At 24 weeks, significantly more participants in the 36 mg/ml condition (14/130, 10.8%) than in the 0 mg/ml condition (1/130, 0.8%) and the CS condition (4/130, 3.1%) were abstinent (relative risk = 14 [95% CI=1.9-104.9] and 3.5 [95% CI=1.2-10.4], respectively). The abstinence rate in the 8 mg/ml condition was 4.6% (6/130).

CONCLUSIONS

When smokers seeking to reduce smoking tried ENDS, few quit smoking in the short term. However, if smokers continued to use an ENDS with cigarette-like nicotine delivery, a greater proportion completely switched to ENDS, as compared with placebo or a cigarette substitute.

IMPLICATIONS

The extent to which use of electronic nicotine delivery systems (ENDS) for smoking reduction leads to cigarette abstinence in smokers with no plans to quit smoking was unclear. This randomized trial found that ENDS with nicotine delivery approaching that of a cigarette are more effective in helping ambivalent smokers to quit cigarette smoking.

Adults who use e-cigarettes have difficulty understanding nicotine concentrations presented as mg/ml and percent nicotine

INTRODUCTION

Nicotine in e-cigarettes typically is labeled as mg/ml or percent nicotine, but these metrics may be difficult to understand. We examined whether adults who use e-cigarettes accurately can compare nicotine concentrations presented as mg/ml and percent and/or can identify the strength of concentrations presented using these metrics.

METHODS

310 adults completed an online survey in 2020. Participants viewed nicotine concentration pairs (e.g., 24 mg/ml vs 3%) and indicated which concentration was stronger or if they were equal. Participants also categorized nicotine concentrations presented as mg/ml (0-60 mg/ml) and percent (0-6%) into strength categories (no nicotine, very low, low, medium, high, very high). "Correct" answers for the strength of each concentration (e.g., 30 mg/ml is "high" nicotine) were based on the subjective opinion of e-cigarette researchers.

RESULTS

When making direct comparisons, adults correctly identified that one concentration was stronger or that both were equivalent about half of the time (8.30 [5.08] of 19). Adults answered correctly more often when the stronger concentration was presented in mg/ml (4.75 [2.74] of 8) than percent (2.54 [2.60] of 8), p < .001). Adults "correctly" identified the strengths of 8.90 (3.22) of 18 nicotine concentrations, with more "correct" responses for mg/ml (5.27 [2.15]) than percent (3.63 [1.71], p < .001). Adults classified concentrations presented as percent as weaker than equivalent concentrations presented as mg/ml.

CONCLUSIONS

Adults had difficulty understanding nicotine concentrations labeled using the most common metrics, especially percent nicotine. A singular, easy-to-understand labeling system may increase public knowledge about the nicotine concentration/strength of vaping products.

First e-cigarette flavor and device type used: Associations with vaping persistence, frequency, and dependence in young adults

INTRODUCTION

Type of e-cigarette flavoring and device during first use might differentiate later e-cigarette use and dependence. This retrospective cross-sectional study examined associations of recalled first nicotine vaping device and flavor used with current vaping frequency/dependence.

METHODS

A young adult cohort from Los Angeles, California, USA completed web-based surveys (N=2553). Using cross-sectional data from 971 reporting ever vaping nicotine, multivariable hurdle regressions tested associations between recalled first flavor (fruit/sweet, menthol/mint, other) and device (Juul, disposable, mod, box, pod, pen, other) vaped with past-30-day vaping status (yes/no) and frequency (1-30 days), and with any vaping dependence symptoms (yes/no) and count (1-10 symptoms).

RESULTS

The most common first-flavor was sweet (71%); the most common first-device was a vape pen (37%), then Juul (22%). First-flavor of mint/menthol (vs. other; adjusted odds ratio [AOR]: 2.22[95%CI=1.16-4.25]), and first-device mod (AOR=2.40[95%CI=1.34-4.31]) and non-Juul pod (2.64[95% CI=1.41-4.92]) (vs. pen) were associated with past-30-day vaping, and twice as many vaping days (ARRs [Adjusted rate ratios] range: 1.96-2.12;ps<0.05). First flavor of mint/menthol (vs. other; AOR: 1.95[95% CI=1.003-3.79) and first device mod, box, non-juul pod and other (AORs range: 2.36-4.01;ps<0.05) were associated with nicotine dependence. First device Juul, mod, box and non-Juul pod were also associated with more dependence symptoms (ARRs range:1.38-1.59;ps<0.05).

CONCLUSIONS

Exposure to mint/menthol and certain devices (mod, box, Juul and non-juul pods) at first e-cigarette use may be associated with more frequent e-cigarette use and nicotine dependence symptoms in young adulthood. Mint/menthol and certain devices warrant consideration in regulation of e-cigarettes based on product characteristics.

IMPLICATIONS

Characteristics (flavor and device type) of first e-cigarette product used were associated with higher usage and more dependence. Pending replication with prospective designs, the findings suggest certain flavors (mint/menthol) and devices (pods, mods) merit consideration in regulation because of their possible link with continued use and dependence among young people.

Electronic nicotine delivery systems: the need for continued regulatory innovation

The recent surge in electronic nicotine delivery systems (ENDS) or electronic cigarette use among both adolescents and adults challenged tobacco regulatory frameworks worldwide. In this article, we review recent US Food and Drug Administration regulatory approaches to tobacco products, including attempts to regulate nicotine concentration and address youth use. We examine recent drives to promote a harm reduction approach in other product markets such as opioids, where the use of methadone and related therapies promote the public health. We describe the potential of a harm reduction framework for ENDS regulation based on tiered nicotine exposure standards coupled with risk-based product distribution controls that would enable ENDS products to meet the 'Appropriate for the Protection of the Public Health' standard required for tobacco product market entry. A harm reduction approach to ENDS regulation could help countries achieve the laudable public health goals of transitioning existing combustion cigarette users to ENDS products while preventing adolescent ENDS use and subsequent nicotine addiction.

Historical Perspective of Proactive and Reactive Regulations of E-cigarettes to Combat Nicotine Addiction

Cigarettes and electronic cigarettes (e-cigarettes) are major sources of exposure to nicotine, an addictive chemical. Although these products are being regulated by the Food and Drug Administration (FDA) under the Tobacco Control Act, specifications about the nicotine content in these products have not been established yet. In e-cigarettes, nicotine concentration ranges from 0 to > 50mg/mL, and the recent e-cigarette devices provide control to change nicotine flux for higher nicotine delivery. Due to the lack of robust regulations in manufacturing, distribution and marketing, e-cigarettes have already infiltrated the market with youth appealing flavors and devices. As a result, the country is facing a youth epidemic of e-cigarette use. The unregulated nicotine levels in both cigarettes and e-cigarettes can lead to repeated and overexposure of nicotine to youth which can lead to the addiction and detrimental effects on their cognitive functions. Over the past decade, the corrective measures being taken by the FDA for cigarette and e-cigarette regulations also should focus on nicotine exposure levels. Before it is too late to prevent youth from lifetime addiction to nicotine, it is important to address the issues of nicotine concentration, nicotine flux and the e-cigarette device regulations while offering adults with smoking disorder less harmful alternatives to cigarettes.

Differences in Switching Away From Smoking Among Adult Smokers Using JUUL Products in Regions With Different Maximum Nicotine Concentrations: North America and the United Kingdom

Introduction

Electronic nicotine delivery systems (ENDS) may improve public health if they facilitate smokers switching away from cigarettes. Conceptually, switching is facilitated when ENDS provide adequate nicotine delivery. Switching rates among smokers who purchased the JUUL System (“JUUL”) were compared in the United Kingdom (UK), where regulations limit nicotine concentration to 20 mg/mL versus North America (N.Am.; United States and Canada), where higher concentrations are available.

Aims and Methods

Adult established smokers (age ≥21, smoked ≥100 cigarettes, smoking some days or every day at baseline) who newly purchased JUUL were recruited into a longitudinal study (UK: N = 1247; N.Am.: N = 8835). Complete switching (no smoking for ≥30 days) was assessed 1, 3, and 6 months after purchase; propensity score matching (PSM) and logistic regression compared switching after adjusting for baseline characteristics.

Results

In both N.Am. and UK, ≥82% of participants reported using the highest JUUL nicotine concentration available (UK: 18 mg/mL; N.Am.: 59 mg/mL). Unadjusted switching rates did not differ at 1 month (17%–18%); unadjusted and adjusted rates were significantly higher in N.Am. (vs. UK) at 3 and 6 months. In the PSM sample, after additional covariate adjustment, rates were significantly higher in N.Am. (vs. UK) at 3 months (31.5% vs. 22.7%; odds ratio [95% confidence interval, CI] = 1.59 [1.25, 2.02]) and 6 months (38.0% vs. 26.0%; odds ratio [95% CI] = 1.79 [1.37, 2.35]).

Conclusions

These results suggest availability of ENDS in nicotine concentrations greater than 20 mg/mL may be associated with increased switching among adult smokers. Differences in smoking and ENDS use characteristics did not explain associations of location and switching; however, between-country differences may be affected by unmeasured factors.

Implications

Switching rates were lower among smokers who purchased the JUUL System (“JUUL”) in the UK, where regulations limit nicotine concentration to 20 mg/mL versus N.Am. (United States and Canada), where higher concentrations are available—before and after controlling for differences in smoking and ENDS use characteristics. These results suggest availability of ENDS in nicotine concentrations greater than 20 mg/mL may be associated with increased switching among adult smokers. Between-country differences may be affected by unmeasured factors; future research should consider these factors and the extent to which regulatory policy environments may explain differences in switching among adult smokers.

A numerical study on capillary-evaporation behavior of porous wick in electronic cigarettes

A mathematical model based on heat and mass transfer processes in the porous wick of electronic cigarettes was established to describe the atomization of e-liquids according to max liquid temperature, vaporization rate and thermal efficiency in a single puff. Dominant capillary-evaporation effects were defined in the model to account for the effects of electrical power, e-liquid composition and porosity of the wick material on atomization and energy transmission processes. Liquid temperature, vaporization rate, and thermal efficiency were predicted using the mathematical model in 64 groups, varying with electrical power, e-liquid composition and wick porosity. Experimental studies were carried out using a scaled-model test bench to validate the model’s prediction. A higher PG/VG ratio in the e-liquid promoted energy transfer for vaporization, and the e-liquid temperature was comparatively reduced at a relatively high power, which was helpful to avoid atomizer overheating. Compared with the other factors, wick porosity affected the thermal efficiency more significantly. The vaporization rate increased with a higher wick porosity in a certain range. The modelling results suggested that a greater wick porosity and a higher PG ratio in e-liquids helped to improve the overall thermal efficiency.

JUUL 'new technology' pods exhibit greater electrical power and nicotine output than previous devices

In 2019, JUUL Labs began marketing in the European Union 'new technology' pods that incorporated a new wick that it claimed provided 'more satisfaction'. In this study, we compared design and materials of construction, electrical characteristics, liquid composition and nicotine and carbonyl emissions of new technology JUUL pods to their predecessors. Consistent with manufacturer's claims, we found that the new pods incorporated a different wicking material. However, we also found that the new pod design resulted in 50% greater nicotine emissions per puff than its predecessor, despite exhibiting unchanged liquid composition, device geometry and heating coil resistance. We found that when connected to the new technology pods, the JUUL power unit delivered a more consistent voltage to the heating coil. This behaviour suggests that the new coil-wick system resulted in better surface contact between the liquid and the temperature-regulated heating coil. Total carbonyl emissions did not differ across pod generations. That nicotine yields can be greatly altered with a simple substitution of wick material underscores the fragility of regulatory approaches that centre on product design rather than product performance specifications.

Effect of an electronic nicotine delivery system with 0, 8, or 36 mg/mL liquid nicotine versus a cigarette substitute on tobacco-related toxicant exposure: a four-arm, parallel-group, randomised, controlled trial

BACKGROUND

Electronic nicotine delivery systems (ENDSs) are used by some smokers to reduce cigarette consumption, but their effectiveness is uncertain. We aimed to examine the extent to which ENDSs or a non-nicotine cigarette substitute influence tobacco-related toxicant exposure and cigarette consumption in smokers interested in smoking reduction.

METHODS

We did a four-arm, parallel-group, randomised controlled trial at two sites in the USA (Penn State University, Hershey, PA, and Virginia Commonwealth University, Richmond, VA). We enrolled adults aged 21-65 years who smoked more than nine cigarettes per day (for at least the past year), with exhaled CO of more than 9 parts per million at screening, who were not currently using an ENDS, and who were interested in reducing smoking but not quitting. Participants were randomised (site-specific with allocation concealment; 1:1:1:1) to receive either a cartomiser-based, pen-style ENDS (eGo-style) paired with 0, 8, or 36 mg/mL liquid nicotine (participants and researchers masked to concentration) or a non-ENDS cigarette-shaped plastic tube that delivered no nicotine or aerosol (cigarette substitute; unmasked) for 24 weeks. Conditions were chosen to reflect a range of nicotine delivery including none (cigarette substitute and 0 mg/mL ENDS), low (8 mg/mL), and cigarette-like (36 mg/mL), and all conditions were paired with smoking reduction instructions. The primary outcome was concentration of the tobacco-specific carcinogen metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL; urinary total) collected at randomisation and at 4, 12, and 24 weeks. Multiple imputation with and without covariate adjustment was used in addition to sensitivity analyses. This trial is registered with ClinicalTrials.gov, NCT02342795.

FINDINGS

Between July 22, 2015, and Nov 16, 2017, 684 individuals were screened and 520 (76%) were enrolled and randomised. 188 (36%) of 520 participants were lost to follow-up by week 24; attrition did not differ by study group (39 [30%] of 130 in the cigarette substitute group, 56 [43%] of 130 in the ENDS with 0 mg/mL nicotine group, 49 [38%] of 130 in the ENDS 8 mg/mL group, and 44 [34%] of 130 in the ENDS 36 mg/mL group). Urinary total NNAL at 24 weeks in the ENDS with 36 mg/mL nicotine group was 210·80 pg/mg creatinine (95% CI 163·03-274·42) compared with 346·09 pg/mg creatinine (265·00-455·32) in the cigarette substitute group (p=0·0061). No other significant differences between groups were observed for any time point for urinary total NNAL. Serious adverse event frequency was similar across groups (12 events in 12 participants [9%] in the ENDS with 36 mg/mL nicotine group, seven events in six participants [5%] in the 8 mg/mL group, 11 events in ten participants [8%] in the 0 mg/mL group, and 13 events in 13 participants [10%] in the cigarette substitute group), and all of these were deemed unrelated or unlikely to be related to study product use. There was one death between randomisation and 24 weeks (suicide; in the ENDS with 0 mg/mL nicotine group).

INTERPRETATION

Use of an ENDS with cigarette-like nicotine delivery can reduce exposure to a major pulmonary carcinogen, NNAL, even with concurrent smoking. Future ENDS trials should involve products with well characterised nicotine delivery, including those with nicotine delivery approaching that of a cigarette.

FUNDING

National Institutes of Health, US Food and Drug Administration.

Potential factors affecting free base nicotine yield in electronic cigarette aerosols

BACKGROUND

The free base and protonated nicotine forms in e-cigarette aerosol have shown different absorption profiles in users. Therefore, it is also important to identify the factors which can affect the ratio of these nicotine forms in the aerosol. Such factors may include nicotine concentrations, flavors, PG:VG ratios, types of nicotine chemical compounds and e-cigarette battery power outputs. The current study attempts to identify such factors using a controlled experiment.

RESEARCH DESIGNS AND METHODS

The aerosol was generated using validated aerosol generating model. Various factors were tested for their effect on nicotine forms. Additionally, a degradation study of one of the nicotine compounds, nicotine salicylate, was also carried out using mass spectrometry.

RESULTS

The free base nicotine in the aerosol was found to be affected by flavors, battery power output, nicotine compound type and PG:VG ratios. Based on the preliminary mass spectrometry data, degradation of nicotine salicylate was found to be one of the significant factors affecting free base nicotine in aerosol.

CONCLUSIONS

Potential factors affecting free base nicotine in e-cigarette aerosol have been identified in this study. These findings would help in understanding the nicotine delivery better and assist for better regulations.

Nicotine pharmacokinetics of electronic cigarettes: A pooled data analysis from the literature

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Evaluating the pharmacokinetics of nicotine absorption from electronic cigarettes.

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Nicotine absorption into the blood is influenced by several factors.

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These include e-liquid composition, user behavior and device characteristics.

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Any regulation of nicotine levels in e-liquids should reflect this heterogeneity.

Several regulatory initiatives around the world restrict the amount of nicotine permitted in electronic cigarette liquids in an attempt to reproduce the nicotine delivery of combusted tobacco products, such as cigarettes, and or reduce the risk of consumers absorbing too much nicotine into their body at one time. Such an approach, however, assumes that (i) there is a strong correlation between the levels of nicotine in electronic cigarette liquids and nicotine intake into the body and (ii) that this correlation holds true across the various different types of electronic cigarette devices currently available on the market. In order to test these hypotheses, this study examines the available scientific literature on nicotine intake from electronic cigarettes, as measured by levels in the blood. Analysis of the published data reveals that nicotine absorption into the body is influenced by a combination of many factors, including electronic cigarette liquid composition, user behavior and device characteristics. Notably, it was observed that open-tank (refillable) electronic cigarettes, which often enable users to vary device power, can deliver high nicotine levels to consumers, sometimes at greater doses than a conventional tobacco cigarette, even at the lower nicotine liquid concentrations typically available. For electronic cigarettes to be viable alternative choices to smoking, they should provide consumers with an equally satisfying experience, including in terms of nicotine absorption into the body. Therefore, any regulation seeking to restrict the amount of nicotine in electronic cigarette liquids should take all the factors influencing nicotine intake into account.

Abuse liability assessment of the JUUL system in two nicotine concentrations compared to combustible cigarette, nicotine gum and comparator electronic nicotine delivery system

BACKGROUND

To assess the abuse liability of the JUUL System (JS) in 5.0 % (59 mg/mL) and 3.0 % (35 mg/mL) nicotine concentrations.

METHODS

Adult smokers (N = 146; 45.9 % female; mean age = 41.29 years) were randomized to one of four study flavor arms and then to a within-subjects cross-over sequence for five test product categories: (1) JS 5.0 % nicotine concentration; (2) JS 3.0 % nicotine; (3) usual brand (UB) cigarette; (4) 4 mg mint nicotine gum; (5) comparator ENDS (VUSE Alto 5.0 % nicotine). Products were tested by ad libitum use (5 min for ENDS and cigarette; 30 min for gum); nicotine pharmacokinetic (PK) parameters and subjective effects were assessed following use.

RESULTS

Maximum plasma nicotine concentration (C_max-BL), rate of plasma nicotine rise and total nicotine exposure (AUC_0-60-BL) of UB cigarette were significantly greater than all other test products. The comparator ENDS was significantly greater than 5.0 % and 3.0 % JS and nicotine gum on C_max-BL, rate of plasma nicotine rise, and AUC_0-60-BL; C_max-BL of JS 5.0 % was significantly greater than JS 3.0 % and nicotine gum. Product liking and satisfying effects were significantly highest for the UB cigarette; JS products and comparator ENDS did not significantly differ and were rated higher than nicotine gum on most subjective measures.

CONCLUSIONS

These results suggest that the abuse liability of both 5.0 % and 3.0 % JS is: (1) substantially lower than UB cigarette; (2) somewhat lower than comparator ENDS; and (3) higher than nicotine gum. Additionally, the abuse liability of JS 5.0 % is somewhat higher than JS 3.0 %.

Abuse liability assessment of the JUUL system in four flavors relative to combustible cigarette, nicotine gum and a comparator electronic nicotine delivery system among adult smokers

BACKGROUND

The abuse liability of the JUUL System (JS) in four flavors were evaluated compared to combustible cigarettes, nicotine gum, and a comparator electronic nicotine delivery system (ENDS) with pharmacokinetics (PK) and subjective effects.

METHODS

Adult smokers (N = 66; 50.0 % female; mean age = 41.1; 63.6 % white) completed a 7-arm within-subjects cross-over product-use study while confined to a clinical laboratory. Participants used JS in four flavors (Virginia Tobacco, Mango, Mint, Creme, [5.0 % nicotine; 59 mg/mL]), their usual brand (UB) cigarette, a comparator ENDS (VUSE Solo; 4.8 % nicotine, tobacco-flavor), and mint nicotine gum (4 mg) under controlled use conditions. After each product use, nicotine PK and subjective effects were assessed.

RESULTS

Maximum plasma nicotine levels (Cmax-BL), rate of plasma nicotine rise, overall nicotine exposure (AUC0-60-BL), and subjective liking and satisfaction of JS were significantly lower than UB cigarettes. These parameters were generally greater for JS than nicotine gum; the comparator ENDS was somewhat lower but within the range of JS. Nicotine PK did not differ among the Mint, Mango, and Virginia Tobacco JS flavors. Mint and Mango were rated as more satisfying than Virginia Tobacco and Creme.

CONCLUSIONS

Controlled use of JS among adult smokers resulted in nicotine delivery, product liking, and satisfaction that were less than that of combustible cigarettes but generally greater than nicotine gum. These results support the conclusion that JS has lower abuse liability than combustible cigarettes, higher abuse liability than nicotine gum, and may provide sufficient nicotine delivery and satisfying effects to support substitution for combustible cigarettes among adult smokers.

E-cigarette use behaviors and device characteristics of daily exclusive e-cigarette users in Maryland: Implications for product toxicity

INTRODUCTION

Few studies to date have characterized daily exclusive e-cigarette users, device characteristics, and use behaviors. This study describes daily e-cigarette user characteristics, and assesses the association between user behaviors and demographics.

METHODS

From 2015–2017, 100 daily exclusive e-cigarette users and 50 non-users were recruited in Maryland, USA. Sociodemographic characteristics, health status, e-cigarette/tobacco use behaviors, device characteristics, and reasons for e-cigarette use were collected by interview. Chi-squared tests (categorical variables), Student’s t-test (continuous variables), and linear regressions were used to assess relationships between variables.

RESULTS

Most daily exclusive e-cigarette users were men, White, former smokers, used MODs/tanks, and vaped on average 365 puffs/day (SD: 720). A third of users first vaped within 5 minutes of waking in the morning, and 56% vaped throughout the day. E-liquid consumption ranged from 5–240 mL/week (median: 32.5), with nicotine concentration 0–24 mg/mL (median: 3). E-cigarette users were more likely to report wheezing/whistling and hypertension than controls, although the finding was not statistically significant after adjustment. Less than half planned to quit vaping.

CONCLUSIONS

Daily e-cigarette users between 2015–2017 most commonly vaped MOD/tank devices. Being male and of lower education was associated with higher usage. Daily users with no intention to quit may be at risk for increased exposure to emissions from e-cigarettes that include inorganic (metals) and organic (e.g. acrolein, formaldehyde) compounds with known toxic effects, particularly to the lung. Further research is needed to characterize the long-term health effects of daily e-cigarette use.

What factors reliably predict electronic cigarette nicotine delivery?

BACKGROUND

The ability of an electronic cigarette (e-cigarette) to deliver nicotine effectively may be dependent on features of the device, the liquid and the user. Some of these features have been examined in previous work (eg, liquid nicotine concentration and puff topography), while others have not (eg, nicotine dependence and demographic characteristics). The purpose of this secondary analysis is to examine such features as predictors of e-cigarette nicotine delivery using a relatively large sample.

METHODS

Four studies were combined in which e-cigarette-experienced users (n=63; 89% men; 75% white) and e-cigarette-naïve cigarette smokers (n=67; 66% men; 54% white) took 10 puffs from an eGo-style e-cigarette (~7.3 watts) filled with liquid that had a nicotine concentration of 18, 25 or 36 mg/mL. Thus, held constant across all studies were device features of battery/cartomiser style and power level and the topography parameters of puff number and interpuff interval. Blood was sampled before and after use, and puff topography was measured. Three general linear models were conducted to predict plasma nicotine concentrations (pre-post increase) for: (1) e-cigarette users only, (2) smokers only and (3) both groups combined. Predictor variables included puff duration, puff volume, liquid nicotine concentration, presession plasma nicotine concentration, nicotine dependence score (smokers only), gender and race.

RESULTS

In all models tested, longer puff durations and higher liquid nicotine concentrations were associated significantly with increased nicotine delivery (ps<0.05). For e-cigarette users only, higher presession nicotine concentration was associated significantly with increased nicotine delivery (p<0.05).

CONCLUSIONS

Puff duration and liquid nicotine concentration may be among the more important factors to consider as regulators attempt to balance e-cigarette safety with efficacy. These findings should be interpreted in the context of devices with relatively low power output, a variable not studied here but likely also directly relevant to product regulation.

E-cigarettes: How can they help smokers quit without addicting a new generation?

The dramatic increase in youth use of electronic nicotine delivery systems (ENDS; e.g., e-cigarettes) in the United States has focused regulatory efforts to address this concern while still encouraging smokers to switch completely to lower risk products or quit all tobacco product use. Increases in the minimum age for purchase of all tobacco products and changes in enforcement policy for ENDS have been recently enacted in an effort to address the youth vaping epidemic. Since all ENDS marketed after February 15, 2007 will be required to meet the "appropriate for the protection of public health" standard for marketing authorization of new products, ENDS manufacturers will have to demonstrate, in part, that their products help lessen the adverse impact on youth use. Some, such as disallowing flavors other than tobacco or menthol or limiting nicotine delivery, may help reduce youth use but could also inhibit smokers from quitting smoking. Other approaches, including reducing the high-tech appearance and discreteness of ENDS, discontinuing use of coupons and two-for-one type price incentives for ENDS, limiting retail sales of these products to adult-only facilities, and incorporating technological innovations such as biometrics or geofencing into ENDS, may help manufacturers demonstrate that marketing of their products would help reduce youth use of ENDS and lessen the epidemic, while still assuring adult smokers have access to products that encourage discontinuing combusted product use.

Nicotine forms: why and how do they matter in nicotine delivery from electronic cigarettes?

INTRODUCTION

Unregulated e-cigarette devices and their nicotine content have amplified the potential of e-cigarettes as addictive agents. Several e-cigarette-related parameters have been identified altering nicotine's absorption profile, so their potential effects on addiction should be considered. Of these factors, nicotine forms (protonated and free base) play a significant role in the addiction potential yet their impact on nicotine's absorption has been studied with limited research.

AREAS COVERED

Current review aims to emphasize on the possible mechanism behind different absorption profiles of nicotine forms considering their physical states (droplet and vapor phase) and the aerosol particle size, their analysis in e-cigarette research and the regulatory attention warranted by them to combat nicotine addiction in the population due to e-cigarettes.

EXPERT OPINION

The protonated form of nicotine is being correlated with the smooth sensory effects and high nicotine absorption as compared to free base nicotine. With the introduction of nicotine salts, which yield mostly the protonated form, the youth popularity of e-cigarettes has spiked exponentially. While it is important to control nicotine levels in e-cigarette products, attention should also be given to the nicotine forms present in these products in order to address nicotine addiction in the population.

Might limiting liquid nicotine concentration result in more toxic electronic cigarette aerosols?

Some jurisdictions have instituted limits on electronic cigarette (ECIG) liquid nicotine concentration, in an effort to control ECIG nicotine yield, and others are considering following suit. Because ECIG nicotine yield is proportional to the product of liquid nicotine concentration (milligram per millilitre) and device power (watts) regulations that limit liquid nicotine concentration may drive users to adopt higher wattage devices to obtain a desired nicotine yield. In this study we investigated, under various hypothetical regulatory limits on ECIG liquid nicotine concentration, a scenario in which a user of a common ECIG device (SMOK TF-N2) seeks to obtain in 15 puffs the nicotine emissions equivalent to one combustible cigarette (ie, 1.8 mg). We measured total aerosol and carbonyl compound (CC) yields in 15 puffs as a function of power (15-80 W) while all else was held constant. The estimated nicotine concentration needed to achieve combustible cigarette-like nicotine yield at each power level was then computed based on the measured liquid consumption. We found that for a constant nicotine yield of 1.8 mg, reducing the liquid nicotine concentration resulted in greater amount of liquid aerosolised (p<0.01) and greater CC emissions (p<0.05). Thus, if users seek a given nicotine yield, regulatory limits on nicotine concentration may have the unintended consequence of increasing exposure to aerosol and respiratory toxicants. This outcome demonstrates that attempting to control ECIG nicotine yield by regulating one factor at a time may have unintended health effects and highlights the need to consider multiple factors and outcomes simultaneously when designing regulations.

Twenty-four-hour subjective and pharmacological effects of ad-libitum electronic and combustible cigarette use among dual users

BACKGROUND AND AIMS

Relative pharmacological effects of e-cigarettes and cigarettes during 24 hours of ad-libitum use have not been described. In this study, 24-hour blood plasma nicotine concentrations and 48-hour subjective effects with use of cigarettes and e-cigarettes were measured among dual users.

DESIGN

Two-arm within-subject cross-over design with preferred e-cigarette or cigarette ad-libitum use over 48 hours.

SETTING

Hospital research ward in San Francisco, California, USA.

PARTICIPANTS

Thirty-six healthy dual users of e-cigarettes and cigarettes (n = 8, 25% females).

MEASUREMENTS

Twenty-four-hour blood plasma nicotine and cotinine concentrations and 48-hour self-reported nicotine withdrawal symptoms and rewarding effects.

FINDINGS

Analyses used analysis of variance (ANOVA)-based mixed models with order of product (e-cigarette or cigarette) and product type (combustible cigarette or type of e-cigarette) as fixed effects, and subject as a repeated effect. During a 24-hour period, e-cigarettes produced lower nicotine exposure than cigarettes for the majority of users, although 25% received more nicotine from e-cigarettes, which was predicted by more frequent e-cigarette use or greater dependence. Compared to cigarette smoking, nicotine exposure for variable-power tank users was similar, while cig-a-like (t₍₃₀₎  = 2.71, P = 0.011, d = 0.745) and fixed-power tank users (t₍₃₀₎  = 3.37, P = 0.002, d = 0.993) were exposed to less nicotine. Cigarettes were rated higher than e-cigarettes on some desirable subjective effects (e.g. psychological reward, t₍₃₂₂₎  = 7.24 P < 0.001, d = 0.432), but withdrawal symptom reduction was comparable. No differences were found between e-cigarette types, but Bayes factors indicate that these measures were insensitive.

CONCLUSIONS

During a 24-hour period in a hospital setting in the United States, nicotine exposure for dual users of e-cigarettes and cigarettes was similar when using cigarettes or variable-power tank devices only but was lower for those using cig-a-like or fixed-power devices only. Despite lower nicotine levels, all types of e-cigarette were effective in preventing withdrawal symptoms. E-cigarettes were rated less rewarding than cigarettes.

Differential effects of nicotine delivery rate on subjective drug effects, urges to smoke, heart rate and blood pressure in tobacco smokers

RATIONALE

The nicotine delivery rate is a key feature of tobacco product design, yet there have been limited human studies examining the effects of nicotine as a function of delivery rate.

OBJECTIVE

We developed an intravenous nicotine infusion protocol to evaluate differential effects of nicotine delivery rate on subjective drug effects, smoking urges, abstinence symptoms, heart rate, and blood pressure.

METHODS

Eighteen non-treatment seeking, overnight abstinent male and female smokers (18 to 30 years old), who smoked ≥ 5 cigarettes per day for the past year completed four sessions, in which they were randomly assigned to a saline infusion, or a 1 mg per 70-kg body weight dose of nicotine delivered over 1, 5, or 10 min at rates of 0.24, 0.048, or 0.024 μg/kg/s, respectively.

RESULTS

Smoking urges, as assessed by the Brief Questionnaire of Smoking Urges, were reduced relative to placebo for the 1- and 5-min infusion, but not the 10-min infusion. Although the 1- and 5-min infusions reduced smoking urges to a similar extent, the 1-min infusion induced a greater heart rate and blood pressure increase. Changes to subjective drug effects, heart rate, and blood pressure delineate the differential effects of nicotine delivery rate for these outcomes.

CONCLUSIONS

We have characterized the delivery rate-response curve for a nicotine dose that is roughly the amount of nicotine (~ 1 mg) delivered by smoking a standard tobacco cigarette. Our findings reinforce the importance of nicotine delivery rate when evaluating the potential effects of nicotine from tobacco products.

A comparison of the electrical characteristics, liquid composition, and toxicant emissions of JUUL USA and JUUL UK e-cigarettes

In 2018, JUUL entered the UK market, where EU regulations limit liquid nicotine concentration to 20 mg/mL, approximately one-third the level of JUUL products sold in the USA. We hypothesized that JUUL's UK product was engineered to deliver greater electrical power and boost liquid vaporization such that the net nicotine delivery rate was similar to the US version. We compared electrical characteristics, liquid composition, and aerosol emissions of JUUL devices procured in the USA and the UK. Study outcomes included electrical power, total and freebase nicotine, propylene glycol/vegetable glycerin ratio, carbonyls, and reactive oxygen species. Liquids and aerosols were analyzed by GCMS, HPLC, and fluorescence. Compared to the US version, JUUL UK had approximately one-third the liquid nicotine concentration in the liquid (5.4 vs. 1.6 wt.%) and aerosol (4.7 and 1.3 wt.%). Other than nicotine concentration and yield, we found no differences in any other study outcome, including electrical power. Currently, JUUL UK emits nicotine at a far lower rate than the US product, offering an opportunity to study how this factor impacts user behavior, JUUL uptake, and other population-level outcomes across the two markets.

Perceived addiction to vaping among youth and young adult regular vapers

BACKGROUND

The prevalence of e-cigarette use among youth and young adults has increased markedly in recent years; however, little is known about young people's perceptions of e-cigarette addiction. This study examines factors associated with self-reported addiction to e-cigarette use among this population.

METHODS

In 2018, 1048 Canadians aged 16-25 years were recruited through online social media platforms to complete a survey. Quota sampling was used to oversample regular e-cigarette users (vaping at least weekly); these 578 regular users were included in this analysis. Self-perceived addiction was assessed by asking participants if they felt they were 'very', 'somewhat' or 'not at all' addicted to e-cigarettes. A proportional odds model was employed to identify factors associated with the ordinal outcome.

RESULTS

Almost half of regular users perceived themselves to be 'not at all addicted', 41% felt they were 'somewhat addicted' and 13% felt they were very addicted to e-cigarettes. Women, former cigarette smokers, daily vapers and those vaping for more than a year were more likely to report higher levels of perceived addiction. Similarly, high sensation-seeking youth, those reading blogs and websites about vaping, those frequently dripping and those using higher nicotine strengths had a greater likelihood of higher perceived addiction than their respective counterparts.

CONCLUSION

More than half of youth and young adult regular e-cigarette users felt they had some level of addiction. The findings identify possible opportunities for targeted programming for education and treatment, as well as potential opportunities for policy change such as maximum allowable nicotine strengths.

Sensory attributes of e-cigarette flavours and nicotine as mediators of interproduct differences in appeal among young adults

OBJECTIVE

To estimate the extent to which specific sensory attributes, for example, smoothness, mediate differences in electronic cigarette (e-cigarette) appeal between products in non-tobacco versus tobacco flavours and varying nicotine content in young adults.

METHOD

E-cigarette users (n=100; aged 18-34 years) administered standardised two-puff e-cigarette doses of different products varying in a flavour (fruit, menthol, tobacco) × nicotine (nicotine-containing (6 mg/mL freebase), nicotine-free) within-subject design. Participants rated sensory attributes (sweetness, bitterness, smoothness and harshness) and appeal on 100-unit visual analogue scales after administering each product. Sensory ratings were tested as simultaneous mediators of flavour, nicotine and flavour × nicotine effects on appeal.

RESULTS

Appeal preferences for fruit versus tobacco flavours were mediated by sweetness-enhancing (β_indirect=0.092), smoothness-enhancing (β_indirect=0.045) and bitterness-reducing (β_indirect=0.072) effects of fruit flavours. Appeal preferences for menthol versus tobacco flavours were mediated by menthol's smoothness-enhancing (β_indirect=0.039) and bitterness-reducing (β_indirect=0.034) effects. Lower appeal of nicotine-containing versus nicotine-free products was mediated by nicotine's sweetness-reducing (β_indirect=-0.036), smoothness-reducing (β_indirect=-0.156) and bitterness-increasing (β_indirect=0.045) effects. Flavour × nicotine interaction effects on appeal were explained by menthol-related suppression of nicotine's bitterness-enhancing and sweetness-reducing mediation pathways and fruit-related suppression of nicotine's bitterness-enhancing mediation pathway. Harshness did not mediate appeal after adjusting for other sensory attributes.

CONCLUSION

Bitterness and smoothness may be cross-cutting mediators of interproduct variation in the effects of types of non-tobacco flavours and nicotine on e-cigarette appeal in young adults. Sweetness may also mediate appeal-enhancing effects of fruit and appeal-reducing effects of nicotine. Non-tobacco flavours may suppress appeal-reducing effects of nicotine in e-cigarettes through attenuation of nicotine's aversive taste attributes.

Influence of electronic cigarette liquid flavors and nicotine concentration on subjective measures of abuse liability in young adult cigarette smokers

BACKGROUND

A rapidly evolving tobacco marketplace highlights the timeliness of the FDA's authority to regulate tobacco, specifically the role that flavorings in nicotine-containing electronic cigarette (ECIG) liquids have on public health. This study aimed to evaluate the extent to which ECIG liquid flavor and nicotine concentration influenced subjective measures of abuse liability among young adult cigarette (cig) smokers.

METHODS

Young adult (18-21 y.o.) smokers (M = 10.1 cig/day, no regular ECIG use history) completed 7 Latin-square ordered conditions each preceded by 12 h. nicotine/tobacco abstinence. Conditions were own brand cig (OB) and eGo-style ECIG paired with three liquid flavors (cream, tropical fruit, tobacco/menthol) varying in nicotine concentration (0 or 36 mg/ml). Products were administered in two 10-puff bouts in each condition. Heart rate/blood pressure (HR/BP) and tobacco/nicotine abstinence symptoms, nicotine/general drug effects, and acceptability measures were assessed repeatedly throughout sessions. Mixed linear models were followed-up with Tukey's HSD t-tests.

RESULTS

HR/BP indicated nicotine exposure during nicotine-containing conditions. OB and tobacco/menthol 36 mg/ml conditions produced significant decreases in ratings of cig smoking urges. Nicotine/drug effects were elevated significantly for OB and 36 mg/ml ECIG conditions with one exception noted for the tobacco/menthol 0 mg/ml condition. OB had the highest acceptability ratings, and ECIG condition results varied by acceptability item.

CONCLUSIONS

Among young adult smokers, ECIG conditions containing nicotine were positively associated with several subjective measures of abuse liability but not all. Flavors did not consistently mask/enhance effects observed. Results reinforce continued examination of ECIG-delivered nicotine and liquid flavors in relationship to abuse liability.

What is the nicotine delivery profile of electronic cigarettes?

Introduction: Electronic cigarettes (e-cigarettes) are a rapidly evolving class of tobacco products intended to deliver nicotine to users. There are many types of e-cigarettes available and the most popular type today in the United States are 'pod' based devices that use high nicotine concentration liquids. Understanding the nicotine delivery capabilities of e-cigarettes is imperative for understanding their addictive potential and safety profile, informing regulation, and revealing their potential use as smoking cessation aids. Areas covered: This review discusses nicotine content of e-cigarettes, effectiveness of nicotine aerosolization by devices, delivery of nicotine to users, and user and device characteristics that impact each of these. Expert opinion: Modern e-cigarettes have the potential to deliver equal or more nicotine compared to a tobacco cigarette. Future research needs to identify the nicotine delivery profiles likely to benefit public health and the means to regulate them appropriately while also identifying those that are likely to cause harm. Public health benefit accrues if e-cigarettes help smokers quit combustible cigarettes completely. Harm is possible if inadequate nicotine delivery undermines cessation attempts, e-cigarettes facilitate continued combustible cigarette use, long-term e-cigarette use is associated with substantial morbidity/mortality, and/or e-cigarettes increase the initiation of combustible cigarette use among never smokers.

Nicotine and Carbonyl Emissions From Popular Electronic Cigarette Products: Correlation to Liquid Composition and Design Characteristics

Introduction

Available in hundreds of device designs and thousands of flavors, electronic cigarette (ECIG) may have differing toxicant emission characteristics. This study assesses nicotine and carbonyl yields in the most popular brands in the U.S. market. These products included disposable, prefilled cartridge, and tank-based ECIGs.

Methods

Twenty-seven ECIG products of 10 brands were procured and their power outputs were measured. The e-liquids were characterized for pH, nicotine concentration, propylene glycol/vegetable glycerin (PG/VG) ratio, and water content. Aerosols were generated using a puffing machine and nicotine and carbonyls were, respectively, quantified using gas chromatograph and high-performance liquid chromatography. A multiregression model was used to interpret the data.

Results

Nicotine yields varied from 0.27 to 2.91 mg/15 puffs, a range corresponding to the nicotine yield of less than 1 to more than 3 combustible cigarettes. Nicotine yield was highly correlated with ECIG type and brand, liquid nicotine concentration, and PG/VG ratio, and to a lower significance with electrical power, but not with pH and water content. Carbonyls, including the carcinogen formaldehyde, were detected in all ECIG aerosols, with total carbonyl concentrations ranging from 3.72 to 48.85 µg/15 puffs. Unlike nicotine, carbonyl concentrations were mainly correlated with power.

Conclusion

In 15 puffs, some ECIG devices emit nicotine quantities that exceed those of tobacco cigarettes. Nicotine emissions vary widely across products but carbonyl emissions showed little variations. In spite of that ECIG users are exposed to toxicologically significant levels of carbonyl compounds, especially formaldehyde. Regression analysis showed the importance of design and e-liquid characteristics as determinants of nicotine and carbonyl emissions.

Implications

Periodic surveying of characteristics of ECIG products available in the marketplace is valuable for understanding population-wide changes in ECIG use patterns over time.

Answering questions about electronic cigarettes using a multidisciplinary model

Electronic cigarettes (ECIGs) are a relatively new class of tobacco products and a subject of much debate for scientists and policymakers worldwide. Objective data that address the ECIG risk-benefit ratio for individual and public health are needed, and addressing this need requires a multidisciplinary approach that spans several areas of psychology as well as chemistry, toxicant inhalation, and physiology. This multidisciplinary approach would benefit from methods that are reliable, valid, and swift. For this reason, we formed a multidisciplinary team to develop methods that could answer questions about ECIGs and other potential modified risk tobacco products. Our team includes scientists with expertise in psychology (clinical, community, and experimental) and other disciplines, including aerosol research, analytical chemistry, biostatistics, engineering, internal medicine, and public health. The psychologists on our team keep other members focused on factors that influence individual behavior, and other team members keep the psychologists aware of other issues, such as product design. Critically, all team members are willing to extend their interests beyond the boundaries of their discipline to collaborate effectively with the shared goal of producing the rigorous science needed to inform empirically based tobacco policy. In addition, our trainees gain valuable knowledge from these collaborations and learn that other disciplines are accessible, exciting, and can enhance their own research. Multidisciplinary work presents challenges: learning other scientists' languages and staying focused on our core mission. Overall, our multidisciplinary team has led to several major findings that inform the scientific, regulatory, and public health communities about ECIGs and their effects. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Discrimination of nicotine content in electronic cigarettes

INTRODUCTION

Behavioral discrimination of nicotine has only recently been assessed in humans, administered mostly by nasal spray before the newly available Spectrum research cigarettes differing in nicotine content. Here we wanted to explore applicability of these procedures to assess discrimination of nicotine administered by e-cigarettes.

METHODS

In this feasibility study, 16 adult smokers were tested on ability to discriminate e-cigarettes with nicotine concentrations of 36, 24, and 12 mg/ml, one per session (in that order), from a placebo (0 mg/ml), each identified only by letter code. Reliable discrimination was defined by accurately identifying which was which (i.e. nicotine vs placebo) on >85% of trials (i.e. ≥7 of 8; p < .05). Subjective perceptions were also assessed.

RESULTS

Discrimination from placebo was shown with 36 mg/ml and with 24 mg/ml nicotine in 15 of 16 subjects, but only 10 discriminated placebo from 12 mg/ml nicotine. Subjective items previously related to acute nicotine exposure ("how much nicotine", "head rush/buzzed" on 0-100 VAS) generally showed nicotine concentration-dependent effects, as expected, but so did "throat irritation".

CONCLUSIONS

Preliminary results confirm feasibility of using our behavioral procedure to assess ability to discriminate nicotine administered via these e-cigarettes, broadening generalizability of this procedure beyond nicotine via nasal spray and smoked tobacco cigarettes. Findings also suggest its applicability with testing discrimination of nicotine via other methods of rapid dosing (e.g., hookah, novel products), including the newer e-cigarette products. Further study with larger samples may identify individual difference and other factors influencing nicotine discrimination administered via e-cigarettes and other products.

Nicotine pharmacokinetics of electronic cigarettes: A review of the literature

E-cigarettes are battery-powered electronic devices from which users can inhale nicotine following its aerosolisation from a liquid solution. Some regulators and public health bodies consider e-cigarettes as potentially playing a major role in tobacco harm reduction. Their ability to provide nicotine to smokers in both amount and in a manner and form generally similar to cigarette smoking have been proposed as key components to help smokers reduce or cease the use of combustible cigarettes. Nicotine pharmacokinetic studies of e-cigarettes have been performed for a number of years and are beginning to show how nicotine delivery is evolving as the products themselves evolve. In this review, we provide a critical overview of the literature to describe what is known about nicotine delivery from e-cigarettes. We will discuss how the progression of e-cigarette design, development, and user familiarity has allowed increases in nicotine availability to the user, in the context of how much and how rapidly nicotine is delivered during acute-use periods. This review will also provide insight into current research gaps and highlight the potential utility of modelling and the standardisation of methodologies used to assess nicotine delivery to facilitate identification of products that are best suited to displace cigarette smoking among adult smokers.

Electronic cigarette liquid and device parameters and aerosol characteristics: A survey of regular users

INTRODUCTION

Electronic cigarettes are widely variable devices, typically with user definable liquid and device parameters. Yet, little is known about how regular users manipulate these parameters. There is also limited understanding of what factors drive electronic cigarette use and liquid purchasing, and whether two common ingredients, propylene glycol and vegetable glycerin, alter the subjective effects of these devices.

METHODS

During the spring of 2016 522 adults, who reported daily use of electronic cigarettes containing nicotine, completed a survey on electronic cigarettes. Survey questions included an electronic cigarette dependence questionnaire, questions on tobacco and electronic cigarette use, and device and liquid preferences.

RESULTS

Fifty-nine percent of respondents reported using another tobacco product, which was positively associated with level of nicotine dependence. On average, devices were set to 28.3 (SD = 24.2) watts. Ability to change device voltage, and level of resistance typically used, was significantly associated with level of nicotine dependence. Amount of liquid consumed, nicotine concentration, and milligrams of nicotine used per week, were positively associated with nicotine dependence. Participants rated 'good taste' as the most important consideration when using and purchasing liquids, and propylene glycol is associated with undesirable effects and vegetable glycerin with desirable effects.

CONCLUSIONS

These data indicate that electronic cigarette users utilize a wide range device parameter settings and liquid variables, and that individuals with greater nicotine dependence favor voltage control devices, and lower resistance heating elements. Taste is a key factor for electronic cigarette selection, and concentrations of propylene glycol and vegetable glycerin may have a significant impact on the reinforcing effects of liquids.