Compensatory Puffing With Lower Nicotine Concentration E-liquids Increases Carbonyl Exposure in E-cigarette Aerosols

Harmful and Potentially Harmful Constituents in E-Liquids and Aerosols from Electronic Nicotine Delivery Systems (ENDS)

In 2012, the U.S. Food & Drug Administration (FDA) published an established list of 93 harmful and potentially harmful constituents (HPHCs) targeting four tobacco product types (cigarettes, cigarette tobacco, roll-your-own tobacco, smokeless tobacco). In 2016, the FDA finalized the deeming rule to regulate electronic nicotine delivery systems (ENDS). However, knowledge gaps exist regarding whether certain HPHCs are present in ENDS e-liquids and aerosols. We identified and addressed these gaps by conducting literature searches and then experimentally quantifying HPHCs in the e-liquid and aerosol of 37 ENDS brands based on gaps in the literature. The literature searches identified 66 e-liquid HPHCs and 68 aerosol HPHCs that have limited to no information regarding the quantifiability of these constituents. A contracted ISO 17025 accredited laboratory performed the HPHC quantifications. The availability of validated analytical methods in the contracted laboratory determined the HPHCs included in the study scope (63/66 for e-liquids, 64/68 for aerosols). Combining the results from the quantifications and literature searches, 36 (39%) and 34 (37%) HPHCs were found quantifiable (≥limit of quantification [LOQ]) in ENDS e-liquids and aerosols, respectively, with 25 HPHCs being quantifiable in both matrices. Quantifiability results imply potential HPHC transfers between matrices, leaching from components, or formations from aerosol generation. The study results can inform the scientific basis for manufacturers and regulators regarding regulatory requirements for HPHC reporting. The HPHC quantities can also inform evaluations of the public health impact of ENDS and public communications regarding ENDS health risks.

Harm perceptions across vaping product features: An on-line cross-sectional survey of adults who smoke and/or vape in the United Kingdom

BACKGROUND AND AIMS

Vaping products are diverse with a wide variety of features, and popular products change rapidly. This study examined the features and types of vaping products that people who smoke and/or vape perceive contribute to the health harms of vaping.

DESIGN, SETTING AND PARTICIPANTS

This was a cross-sectional survey co-designed with adults who smoked/vaped and pre-registered. An on-line survey (November 2022) was used of a convenience sample of adults in the United Kingdom who smoked and/or vaped (n = 494).

MEASUREMENTS

As primary outcomes, respondents were asked to select any of 15 vaping product features they perceived might have any effect on the health harms of vaping (for each: selected, not selected). Independent variables were smoking/vaping status (smoke and vape; vape, formerly smoked; vape, never regularly smoked; smoke, do not currently vape); relative vaping harm perceptions [less harmful than smoking (accurate), equally/more harmful than smoking or do not know/refused (other)]. Binary logistic regressions were used to compare outcomes by current vaping/smoking status and relative harm perceptions, adjusting for age and sex.

FINDINGS

Most people (54.7%) selected between one and three features. The most frequently selected were nicotine concentration (62.2%) and amount of e-liquid consumed (59.1%), followed by nicotine type (e.g. salt or freebase; 33.0%), source/purchase location (25.3%), flavours (24.7%), temperature to heat e-liquid (21.1%), heat produced by device (20.9%), e-liquid brand (20.9%), amount of emissions (18.6%), device type (e.g. disposable, pod, tank; 17.2%), material of tank (17.0%), power/wattage (13.0%), device brand (8.1%), device size (4.1%) and device weight (2.4%). Higher nicotine concentrations, more e-liquid and salt (versus freebase) nicotine were perceived to confer greater harms. Disposables were perceived as slightly more harmful than reusable devices. There were few differences by current vaping/smoking status and between those with accurate (versus other) harm perceptions of vaping relative to smoking (P > 0.05 for most contrasts, adjusting for age and sex).

CONCLUSIONS

Certain features and types of vaping products [higher nicotine concentrations, more e-liquid consumed and salt (versus freebase) nicotine] were perceived to confer greater health harms among a sample of UK adults who smoked and/or vaped. Findings are consistent with pervasive misperceptions that nicotine is a major cause of harm, although e-liquid volume is likely to contribute to harms.

An observational human laboratory assessment of nicotine delivery, vaping topography and subjective effects of usual brand electronic cigarette use among young adults

AIMS

To measure nicotine delivery, vaping topography and subjective effects of current generations of disposable, cartridge-based and other types of electronic cigarettes (e-cigarettes) among young adults.

DESIGN, SETTING, PARTICIPANTS

Observational, human laboratory assessment of e-cigarette use in Columbus, Ohio, USA (July 2020 to June 2021). Participants (n = 96, 60.4% female, age mean = 21.7 [standard deviation = 1.7] years, 82.4% white race) were identified via their participation in a cohort study or other convenience sampling and were 18 to 25 years old, vaped ≥4 days/week for ≥4 weeks and used other tobacco products for ≤5 days of past 30 days. Participants completed a pre-vaping questionnaire, vaped their usual brand of e-cigarette ad libitum for 30 min and completed a post-vaping questionnaire.

MEASUREMENTS

Outcome variables included pre- and post-vaping measures of plasma nicotine (t = 0 and t = 30, respectively) and craving and withdrawal symptoms, as well as vaping topography (e.g. flow rate and inter-puff interval), pre-vaping expectancies and post-vaping product appeal. Variables used to characterize the sample included demographics, e-cigarette and other tobacco use history, e-cigarette dependence and e-cigarette device characteristics (e.g. device type, flavor and nicotine form).

FINDINGS

Participants reported moderate nicotine dependence on average via the E-Cigarette Dependence Scale (mean = 6.9 [standard deviation = 4.0]). Following 30 min of ad libitum vaping, participants achieved substantial plasma nicotine boost (mean = 18.8 [standard deviation = 14.5] ng/mL), corresponding with statistically significant decreases in withdrawal symptoms measured via the Minnesota Nicotine Withdrawal Scale (pre-vaping mean = 9.0 [standard deviation = 5.1], post-vaping mean = 4.3 [standard deviation = 3.9]; P-value <0.0001). Pre-vaping, participants reported moderate vaping expectancies (e.g. mean = 2.5 [standard deviation = 1.0] on a scale from 0 to 4 for smell and taste expectancies); post-vaping, participants reported high satisfaction (mean = 4.6 [standard deviation = 1.2] on a scale from 1 to 7) and moderate reward (mean = 2.9 [standard deviation = 1.2]) and respiratory sensations (mean = 3.7 [standard deviation = 1.6]). Nearly half of participants (47.9%) used disposable e-cigarettes, and most used a mint/menthol or fruit flavored (99.0%) and nicotine salt (98.9%) e-liquid.

CONCLUSIONS

Among young adults in the United States, the latest generations of e-cigarettes appear to deliver large quantities of nicotine (similar to cigarettes) and significantly relieve withdrawal symptoms, and they are appealing.

Toxicological Aspects Associated with Consumption from Electronic Nicotine Delivery System (ENDS): Focus on Heavy Metals Exposure and Cancer Risk

Tobacco smoking remains one of the leading causes of premature death worldwide. Electronic Nicotine Delivery Systems (ENDSs) are proposed as a tool for smoking cessation. In the last few years, a growing number of different types of ENDSs were launched onto the market. Despite the manufacturing differences, ENDSs can be classified as "liquid e-cigarettes" (e-cigs) equipped with an atomizer that vaporizes a liquid composed of vegetable glycerin (VG), polypropylene glycol (PG), and nicotine, with the possible addition of flavorings; otherwise, the "heated tobacco products" (HTPs) heat tobacco sticks through contact with an electronic heating metal element. The presence of some metals in the heating systems, as well as in solder joints, involves the possibility that heavy metal ions can move from these components to the liquid, or they can be adsorbed into the tobacco stick from the heating blade in the case of HTPs. Recent evidence has indicated the presence of heavy metals in the refill liquids and in the mainstream such as arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni), copper (Cu), and lead (Pb). The present review discusses the toxicological aspects associated with the exposition of heavy metals by consumption from ENDSs, focusing on metal carcinogenesis risk.

E-cigarette puffing topography: The importance of assessing user behaviour to inform emissions testing

Analysis of the chemical composition of e-cigarette emissions is an important step in determining whether e-cigarettes offer both individual and population-level harm reduction potential. Commonly, e-cigarette emissions for chemical analysis are collected when using e-cigarettes according to standardised puffing regimens, such as those recommended by the International Organization for Standardization (ISO) or the Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA). While the use of such standard puffing regimens affords a degree of uniformity between studies and are also recommended by regulatory authorities who require the submission of e-cigarette emissions data to make decisions regarding allowing a product to be commercially marketed, the standardised regimens do not necessarily reflect human puffing behaviour. This can lead to under- or over-estimating real-world emissions from e-cigarettes and inaccuracy in determining their harm reduction potential. In this review, we describe how human puffing behaviour (topography) information can be collected both in the clinical laboratory and in the real world using a variety of different methodologies. We further discuss how this information can be used to dictate e-cigarette puffing regimens for collecting emissions for chemical analyses and how this may lead to better predictions both of human yields of e-cigarette emissions constituents and of risk assessments to predict e-cigarette tobacco harm reduction potential.

Examination of the impact of myblu electronic nicotine delivery system e-liquid nicotine strength on self-reported measures of dependence

BACKGROUND

Greater nicotine delivery is associated with higher nicotine concentrations in electronic nicotine delivery system (ENDS) liquids. However, there is a current debate as to whether this leads to increased dependence and mitigates ENDS public health potential.

METHODS

Self-reported dependence among users of myblu ENDS containing different nicotine concentrations was examined with data from a multiwave cross-sectional survey of US young adults and adults. Questions examined responses related to dependence measures and participants' most often used myblu ENDS nicotine concentration (low: 0%, 1% and 1.2%; medium: 2%, 2.4% and 2.5%; or high: 3.6% and 4%).

RESULTS

A global general linear model using nicotine concentration, age and days myblu that was used in the past 30 revealed a significant difference in PROMIS scores among nicotine concentration groups (F = 4.07, p = 0.02). However, pairwise comparisons to examine which specific groups differed significantly from others showed no significant differences. Logistic regression demonstrated that strong past 30-day cravings to use myblu among participants using high or medium nicotine concentrations were not significantly different from those using a low concentration (ORs 0.66 [0.42, 1.03], p = 0.07 and 0.95 [0.49, 1.82], p = 0.98, respectively). Time to daily first use for high or medium nicotine concentration users was not significantly different from those using a low concentration (ORs 0.89 [0.70, 1.14], p = 0.35 and 0.84 [0.57, 1.25], p = 0.40, respectively).

CONCLUSIONS

Use of myblu ENDS with different nicotine concentrations is not associated with differing levels of dependence. Our findings contradict the notion that high ENDS e-liquid nicotine levels generate increased dependence.

Beyond the label: current evidence and future directions for the interrelationship between electronic cigarettes and mental health

Electronic cigarette use has dramatically increased over the last decade. With this recent technological development and wide range of constituents in various products, putative adverse effects on the brain and body have been largely unexplored. Here, we review current evidence linking electronic nicotine cigarette use with potential health consequences and provide evidence supporting an association between drug use and depression in humans. We also examine the biological effects of individual constituents in electronic cigarette aerosols, which include labeled ingredients, such as propylene glycol, vegetable glycerin, nicotine, and flavorants, as well as unlabeled ingredients found in the aerosols, such as carbonyls and heavy metals. Lastly, we examine the effects of electronic cigarette use on endogenous metabolism via changes in cytochrome P450 enzymes, which can thereby impact therapeutic outcomes. While the current evidence offers insight into the potential effects of electronic cigarette use on biological processes, further studies are necessary to determine the long-term clinical relevance of aerosol inhalation.

Nicotine Intake in Adult Pod E-cigarette Users: Impact of User and Device Characteristics

INTRODUCTION

This study examined user behavior, e-cigarette dependence, and device characteristics on nicotine intake among users of pod-mod e-cigarettes.

AIMS AND METHODS

In 2019-2020, people who use pod-mods in the San Francisco Bay Area completed questionnaires and provided a urine sample for analysis of total nicotine equivalents (TNE). The relationship between TNE and e-cigarette use, e-cigarette brands, e-liquid nicotine strength, e-cigarette dependence, and urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), as a measure of combustible cigarette exposure, were examined.

RESULTS

Of 100 participants (64% male, 71% in the 18-34 age group, 45% white), 53 used JUUL primarily, 12 used Puff Bar primarily, and 35 used other brands, including Suorin; 48 participants reported current cigarette smoking. Participants most often reported use of e-liquid with 4.5%-6.0% nicotine (68%), fruit (35%), tobacco (28%), and menthol or mint flavors (26%), used e-cigarettes on 25.5 (SD = 6.3) days a month, 10.2 (SD = 14.2) times a day, and 40% used 1-2 pods/cartridges per week. In bivariate analysis, urinary TNE was higher with greater frequency (days used) and intensity (number of pods used) of e-cigarette use, e-cigarette dependence, and combustible cigarette use. In multivariable analysis, days of e-cigarette use in the last 30 days, number of pods used per week, and NNAL levels were significantly associated with TNE. There was no significant impact of e-liquid nicotine strength on TNE.

CONCLUSIONS

Nicotine intake among people who used pod-mod e-cigarettes increased with e-cigarette consumption and e-cigarette dependence, but not with e-liquid nicotine strength. Our findings may inform whether FDA adopts a nicotine standard for e-cigarettes.

IMPLICATIONS

The study examined how device and user characteristics influence nicotine intake among pod-mod e-cigarette users. Nicotine intake increased with frequency (days of e-cigarette use in past 30 days) intensity of use (number of pods used per day) and e-cigarette dependence but not with the flavor or nicotine concentration of the e-liquids. Regulation of nicotine concentration of e-liquids is unlikely to influence nicotine exposure among adult experienced pod-mod users.

Two Different Heated Tobacco Products vs. Cigarettes: Comparison of Nicotine Delivery and Subjective Effects in Experienced Users

Heated tobacco products (HTPs) produce aerosol using a different mechanism than tobacco cigarettes, leading to lower emissions of some harmful substances, but also of nicotine as reported by some independent studies. Lower nicotine delivery could lead to compensatory puffing when product use does not sufficiently satisfy cravings. Thus, this three-arm crossover study was conducted to characterize the potential of two different HTPs to deliver nicotine and satisfy cravings compared with conventional cigarettes in users who had already switched to HTPs. Fifteen active, non-exclusive HTP users consumed the study products according to a pre-directed puffing protocol. At predetermined time points, venous blood was sampled and the subjective effects of consumption were assessed. Nicotine delivery by both HTPs was comparable, but significantly lower than that by conventional cigarettes, suggesting a lower addictive potential. Cravings were reduced by all products, with no statistically significant differences between them, despite the different nicotine deliveries. This indicated that HTPs do not necessarily need high nicotine deliveries with high addictive potential, as are characteristic of tobacco cigarettes. These results were followed up on with an ad libitum use study.

Investigating #vapingcessation in Twitter

Evidence suggests that an increasing number of e-cigarette users report intentions and attempts to quit vaping. Since exposure to e-cigarette-related content on social media may influence e-cigarette and other tobacco product use, including potentially e-cigarette cessation, we aimed to explore vaping cessation-related posts on Twitter by utilizing a mixed-methods approach. We collected tweets pertaining to vaping cessation for the time period between January 2022 and December 2022 using snscrape. Tweets were scraped for the following hashtags: #vapingcessation, #quitvaping, and #stopJuuling. Data were analysed using Azure Machine Learning and Nvivo 12 software. Sentiment analysis revealed that vaping cessation-related tweets typically embody positive sentiment and are mostly produced in the U.S. and Australia. Our qualitative analysis identified six emerging themes: vaping cessation support, promotion of vaping cessation, barriers and benefits to vaping cessation, personal vaping cessation, and usefulness of peer support for vaping cessation. Our findings imply that improved dissemination of evidence-based vaping cessation strategies to a broad audience through Twitter may promote vaping cessation at the population level.

Assessment of Abuse-Related Discriminative Stimulus Effects of Nicotine Aerosol in Rodents

The rapid increase in e-cigarette use highlights the importance of developing relevant, predictive animal models exploring their potential health implications. The goal of the present study was to examine the abuse-related effects of brief, repeated e-cigarette aerosol exposures in rodents modeling human e-cigarette user behavior. We evaluated the discriminative stimulus effects of brief, repeated puffs of inhaled nicotine in rats that had been trained to discriminate injected nicotine from saline. Locomotor activity measurement following exposure to injected and aerosolized nicotine was also assessed as an additional behavioral outcome. We hypothesized that the stimulus effects of nicotine aerosol were central nervous system (CNS)-mediated and comparable to that produced by an injected nicotine training stimulus. We further hypothesized that number of aerosol puffs and the e-liquid nicotine concentration which was aerosolized would impact the substitution of nicotine aerosol for injected nicotine. Both nicotine injections and exposures to nicotine aerosol produced a dose-dependent effect on locomotor activity. Nicotine aerosol under our puffing conditions produced e-liquid nicotine concentration-dependent and puff-number-dependent complete substitution for the injected nicotine training condition. The nicotinic antagonist, mecamylamine, completely blocked nicotine-appropriate responding produce by the training dose of 0.3 mg/kg injected nicotine as well as that resulting from exposure to aerosol puffs generated by e-liquid containing 3 mg/ml nicotine, demonstrating that the stimulus of inhaled nicotine was most likely CNS-mediated and not due to olfactory stimulus properties. Overall, the results support the hypothesis that an aerosol exposure drug discrimination model in rodents has applicability to studying the abuse-related effects of e-cigarettes. SIGNIFICANCE STATEMENT: Animal models of nicotine aerosol exposure using testing conditions resembling human e-cigarette use are lacking. In this study, we test a novel preclinical model of nicotine vaping in rodents which allows for the exploration of the abuse-related effects of e-cigarettes. This model has the potential to contribute both to our understanding of the abuse-related pharmacological effects of e-cigarettes as well as aid in the development of rationale, evidence-based e-cigarette regulatory policies.

Usage Pattern and Nicotine Delivery during Ad Libitum Consumption of Pod E-Cigarettes and Heated Tobacco Products

Many different nicotine delivery products, such as e-cigarettes (e-cigs) or heated tobacco products (HTPs), are available on the market. To better understand these products, it is crucial to learn how consumers use them and how much nicotine they deliver. Therefore, a pod e-cig, an HTP, and a conventional cigarette (CC) were each used by 15 experienced users of the respective product category for 90 min without special use instructions ("ad libitum"). Sessions were video recorded to analyze usage patterns and puff topography. At defined time points, blood was sampled to determine nicotine concentrations, and subjective effects were inquired about using questionnaires. During the study period, the CC and HTP groups averaged the same number of consumption units (both 4.2 units). In the pod e-cig group, the highest number of puffs was taken (pod e-cig 71.9; HTP: 52.2; CC: 42.3 puffs) with the most extended mean puff duration (pod e-cig: 2.8 s; HTP: 1.9 s; CC: 1.8 s). Pod e-cigs were predominantly used with single puffs or in short clusters of 2-5 puffs. The maximum plasma nicotine concentration was highest for CCs, followed by HTPs, and then pod e-cigs with 24.0, 17.7, and 8.0 ng/mL, respectively. Craving was reduced by all products. The results suggest that the high nicotine delivery known for tobacco-containing products (CCs and HTPs) may not be needed for non-tobacco-containing products (pod e-cigs) to satisfy cravings in experienced users.

Electronic cigarette use intensity measurement challenges and regulatory implications

Assessing tobacco use intensity allows researchers to examine tobacco use in greater detail than assessing ever or current use only. Tobacco use intensity measures have been developed that are specific to tobacco products, such as asking smokers to report number of cigarettes smoked per day. However, consensus on electronic cigarette use intensity measures that can be used for survey research has yet to be established due to electronic cigarette product and user behavior heterogeneity. While some survey measures that attempt to assess electronic cigarette use intensity exist, such as examining number of 'times' using an electronic cigarette per day, number of puffs taken from an electronic cigarette per day, volume of electronic cigarette liquid consumed per day, or nicotine concentration of electronic cigarette liquid, most measures have limitations. Challenges in electronic cigarette measurement often stem from variations across electronic cigarette device and liquid characteristics as well as the difficulty that many electronic cigarette users have regarding answering questions about their electronic cigarette device, liquid, or behavior. The inability for researchers to measure electronic cigarette use intensity accurately has important implications such as failing to detect unintended consequences of regulatory policies. Development of electronic cigarette use intensity measures, though not without its challenges, can improve understanding of electronic cigarette use behaviors and associated health outcomes and inform development of regulatory policies.

Time course of changes in inflammatory and oxidative biomarkers in lung tissue of mice induced by exposure to electronic cigarette aerosol

Significance

Electronic cigarettes (e-cigarettes) have become a popular way to smoke all over the world. Chronic exposure to e-cigarette aerosol may influence lung health. This study uses an animal model to explore the time course of the effect of exposure to e-cigarette aerosols on the lung.

Methods

Lung samples were collected after exposure of Balb/c mice to e-cigarette aerosols for 1 h/day (6 times/week) for 1, 2 and 4 weeks and compared to sham-exposed controls. Examined biomarkers including inflammatory cells, tumor necrosis factor α (TNFα), interleukin-6 (IL-6), interleukin-10 (IL-10), reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione peroxidase (GPx), catalase, superoxide dismutase (SOD), and Thiobarbituric acid reactive substances (TBARS).

Results

Exposure of animals to e-cigarette aerosols induced significant increases (P < 0.05) in total inflammatory cells, eosinophils, macrophages and TNFα in the lung tissue after 1, 2 and 4 weeks of exposure. Furthermore, level of IL-10 significantly decreased, whereas levels of neutrophils and basophils significantly increased (P < 0.05) after 1 week of exposure. Exposure of animals to e-cigarette aerosol also induced significant decreases (P < 0.05) in the GSH/GSSG ratio, and GPx levels after 2 and 4 weeks of exposures. The activity of catalase was also reduced (P < 0.05) after 4 weeks of exposure. Level of TBARS showed a trend of elevation with time and it reached a significant elevation after 4 weeks (P < 0.01).

Conclusion

Current results indicate that inhalation of unflavored e-cigarette aerosol might be associated with inflammation in lung tissue that worsen as the duration of exposure increases. Further experiments including more time points, histopathology and pulmonary physiology experiments are needed to confirm the current results.

On the toxicity of e-cigarettes consumption: Focus on pathological cellular mechanisms

Tobacco smoking remains without a doubt one of the leading causes of premature death worldwide. In combination with conventional protocols for smoking cessation, e-cigarettes have been proposed as a useful tool to quit smoking. Advertised as almost free of toxic effects, e-cigarettes have rapidly increased their popularity, becoming a sought-after device, especially among young people. Recently some health concerns about e-cigarette consumption are being raised. It is well known that they can release several toxic compounds, some of which are carcinogenic to humans, and emerging results are now outlining the risks related to the onset of respiratory and cardiovascular diseases and even cancer. The present review shows the emerging evidence about the role of technical components of the devices, the e-liquid composition as well as customization by consumers. The primary topics we discuss are the main toxicological aspects associated with e-cigarette consumption, focusing on the molecular pathways involved. Here it will be shown how exposure to e-cigarette aerosol induces stress/mitochondrial toxicity, DNA breaks/fragmentation following the same pathological pathways triggered by tobacco smoke, including the deregulation of molecular signalling axis associated with cancer progression and cell migration. Risk to fertility and pregnancy, as well as cardiovascular risk associated with e-cigarette use, have also been reported.

A Review of Toxicity Mechanism Studies of Electronic Cigarettes on Respiratory System

Electronic cigarettes (e-cigarettes) have attracted much attention as a new substitute for conventional cigarettes. E-cigarettes are first exposed to the respiratory system after inhalation, and studies on the toxicity mechanisms of e-cigarettes have been reported. Current research shows that e-cigarette exposure may have potentially harmful effects on cells, animals, and humans, while the safety evaluation of the long-term effects of e-cigarette use is still unknown. Similar but not identical to conventional cigarettes, the toxicity mechanisms of e-cigarettes are mainly manifested in oxidative stress, inflammatory responses, and DNA damage. This review will summarize the toxicity mechanisms and signal pathways of conventional cigarettes and e-cigarettes concerning the respiratory system, which could give researchers a better understanding and direction on the effects of e-cigarettes on our health.

Developmental Effects of Electronic Cigarette Use

Electronic cigarettes have gained widespread acceptance among adolescents and young adults. As a result of this popularity, there are concerns regarding the potential harm of primary, secondhand and thirdhand electronic cigarette exposures on fetal and postnatal development. In vitro studies have shown that constituents in electronic cigarette liquids, including nicotine, flavorings, and carrier agents can alter cellular processes and growth. Additionally, aerosolized electronic cigarette emissions have been shown to disrupt organ development and immune responses in preclinical studies. In clinical studies, an association between electronic cigarette use and frequent respiratory symptoms, greater asthma severity and impaired mucociliary clearance has been demonstrated with adolescent and young adult users of electronic cigarettes having twice the frequency of cough, mucus production, or bronchitis compared to nonusers. Along with the popularity of electronic cigarette use, secondhand electronic cigarette exposure has increased substantially; with almost one-fourth of middle and high school children reporting exposure to secondhand vapors. The health consequences of secondhand electronic cigarette exposure on children and other vulnerable populations are poorly understood but detectable levels of cotinine have been measured in nonusers. Pregnant women and their offspring are another vulnerable group at increased risk for health consequences from electronic cigarette exposure. Nicotine crosses the placenta and can disrupt brain and lung development in preclinical studies. This article will focus on the physiological and health effects associated with primary or secondhand exposure to electronic cigarettes. It is expected that with ongoing availability of electronic cigarettes as well as the accumulation of additional follow-up time for long-term outcomes, the risks associated with exposure will become better clarified. © 2022 American Physiological Society. Compr Physiol 12:3337-3346, 2022.

[Diversification of smoking cessation programmes-the role of e-cigarettes]

The question of whether e‑cigarettes are a useful tool for smoking cessation is part of an ongoing and highly controversial scientific debate. In practice, however, the number of people trying to quit tobacco consumption by using these products is steadily increasing. This discussion article provides an outline of the current state of research on the issue of whether and to what extent e‑cigarettes can help people quit smoking.Of course, e‑cigarettes also have a certain potential for harm, especially if nicotine dependence is unnecessarily prolonged. Nevertheless, it can make an important contribution to harm reduction in nicotine consumption. Hence, the product should get treated as a serious alternative to nicotine replacement therapies (NRTs) in the scientific discussion. Like NRTs, e‑cigarettes offer a less harmful way of consuming nicotine that greatly reduces many of the health risks associated with tobacco consumption, such as the absorption of carcinogenic substances. Recent studies and reviews suggest that the product can be at least as effective as nicotine replacement therapies in helping people quit smoking. Individual studies even demonstrate the increased effectiveness of e‑cigarettes in supporting smoking cessation.Nevertheless, the review of the current literature shows that more high-quality research is needed to further understand the product and its properties. In terms of the harm reduction approach, however, it would already be more appropriate to also rely on e‑cigarettes instead of trying to force immediate and complete nicotine abstinence. After all, in the process of quitting smoking, the fastest possible cessation of the more unhealthy consumption of tobacco should be prioritized in order to immediately minimize unnecessary health risks.

Nominal Operating Envelope of Pod and Pen Style Electronic Cigarettes

Many Electronic Nicotine Delivery Systems (ENDS) employ integrated sensors to detect user puffing behavior and activate the heating coil to initiate aerosol generation. The minimum puff flow rate and duration at which the ENDS device begins to generate aerosol are important parameters in quantifying the viable operating envelope of the device and are essential to formulating a design of experiments for comprehensive emissions characterization. An accurate and unbiased method for quantifying the flow condition operating envelope of ENDS is needed to quantify product characteristics across research laboratories. This study reports an accurate, unbiased method for measuring the minimum and maximum aerosolization puff flow rate and duration of seven pod-style, four pen-style and two disposable ENDS. The minimum aerosolization flow rate ranged from 2.5 to 23 (mL/s) and the minimum aerosolization duration ranged from 0.5 to 1.0 (s) across the ENDS studied. The maximum aerosolization flow rate was defined to be when the onset of liquid aspiration was evident, at flow rates ranging from 50 to 88 (mL/s). Results are presented which provide preliminary estimates for the effective maximum aerosolization flow rate and duration envelope of each ENDS. The variation in operating envelope observed between ENDS products of differing design by various manufacturers has implications for development of standardized emissions testing protocols and data reporting required for regulatory approval of new products.

Clinical Pharmacology of Electronic Nicotine Delivery Systems (ENDS): Implications for Benefits and Risks in the Promotion of the Combusted Tobacco Endgame

Electronic nicotine delivery systems (ENDS) such as e-cigarettes and heated tobacco products are novel battery-operated devices that deliver nicotine without combustion of tobacco. Because cigarette smoking is sustained by nicotine addiction and the toxic combustion products are mainly responsible for the harmful effects of smoking, ENDS could be used to promote smoking cessation while exposing users to lower levels of toxicants compared with conventional cigarettes. The currently available evidence from clinical and observational studies indicates a potential role of e-cigarettes as smoking cessation aids, although many continue to use e-cigarettes long after quitting smoking. Nicotine and toxicant delivery vary considerably by device and depend on the characteristics of the e-liquid formulation. Because smokers tend to titrate their nicotine intake to maintain their desired pharmacologic effects, device and liquid characteristics need to be considered when using ENDS as an aid to quit smoking. Factors potentially limiting their use are the currently still unknown long-term safety of these products and concerns regarding widespread use among youth. Implications of clinical pharmacology data on ENDS for the cigarette endgame and regulation by the U.S. Food and Drug administration are discussed.

Trends in use of e-cigarette device types and heated tobacco products from 2016 to 2020 in England

This study examined use trends of e-cigarette devices types, heated tobacco products (HTPs) and e-liquid nicotine concentrations in England from 2016 to 2020. Data were from a representative repeat cross-sectional survey of adults aged 16 or older. Bayesian logistic regression was used to estimate proportions and 95% credible intervals (CrIs). Of 75,355 participants, 5.3% (weighted = 5.5%) were currently using e-cigarettes or HTPs, with the majority (98.7%) using e-cigarettes. Among e-cigarette users, 53.7% (CrI 52.0-55.1%) used tank devices, 23.7% (22.4-25.1%) mods, 17.3% (16.1-18.4%) pods, and 5.4% (4.7-6.2%) disposables. Tanks were the most widely used device type throughout 2016-2020. Mods were second until 2020, when pods overtook them. Among all e-cigarette/HTP users, prevalence of HTP use remains rare (3.4% in 2016 versus 4.2% in 2020), whereas JUUL use has risen from 3.4% in 2018 to 11.8% in 2020. Across all years, nicotine concentrations of ≤ 6 mg/ml were most widely (41.0%; 39.4-42.4%) and ≥ 20 mg/ml least widely used (4.1%; 3.4-4.9%). Among e-cigarette/HTP users, ex-smokers were more likely than current smokers to use mod and tank e-cigarettes, but less likely to use pods, disposables, JUUL and HTPs. In conclusion, despite growing popularity of pods and HTPs worldwide, refillable tank e-cigarettes remain the most widely used device type in England.

The Time Course of Compensatory Puffing With an Electronic Cigarette: Secondary Analysis of Real-World Puffing Data With High and Low Nicotine Concentration Under Fixed and Adjustable Power Settings

INTRODUCTION

In a secondary analysis of our published data demonstrating compensatory vaping behavior (increased puff number, puff duration, and device power) with e-cigarettes refilled with low versus high nicotine concentration e-liquid, here we examine 5-day time course over which compensatory behavior occurs under fixed and adjustable power settings.

AIMS AND METHODS

Nineteen experienced vapers (37.90 ± 10.66 years, eight females) vaped ad libitum for 5 consecutive days under four counterbalanced conditions (ie, 20 days in total): (1) low nicotine (6 mg/mL)/fixed power (4.0 V/10 W); (2) low nicotine/adjustable power; (3) high nicotine (18 mg/mL)/fixed power; (4) high nicotine/adjustable power (at 1.6 Ohm). Puff number, puff duration, and power settings were recorded by the device. For each day, total daily puffing time was calculated by multiplying daily puff number by mean daily puff duration.

RESULTS

A significant day × setting interaction revealed that whilst puffing compensation (daily puffing time) continued to increase over 5 days under fixed power, it remained stable when power settings were adjustable. Separate analysis for puff number and puff duration suggested that the puffing compensatory behavior was largely maintained via longer puff duration.

CONCLUSIONS

Under fixed power conditions (4.0 V/10 W), vapers appear to compensate for poor nicotine delivery by taking longer puffs and this compensatory puffing appears to be maintained over time.

IMPLICATIONS

Studies in smokers suggest that when switching to lower nicotine levels, compensation for poorer nicotine delivery is transient. Our novel findings suggest that vapers show a different pattern of compensation which is influenced by both nicotine strength and device power settings. When power is fixed (4.0 V; 10 W), compensation (via more intensive puffing) appears prolonged, persisting up to 5 days. Under adjustable settings when power is increased, puffing patterns remain stable over time. Implications of such compensatory behaviors for product safety and user satisfaction need further exploration.

The consequential impact of JUUL on youth vaping and the landscape of tobacco products: The state of play in the COVID-19 era

JUUL is a groundbreaking electronic cigarette (e-cig) and the preeminent vaping product on the market. We present an overview of the rapid and spectacular rise of JUUL and its remarkable fall within the timespan of 2015 - 2020. We highlight JUUL's entering the market in June 2015, becoming the industry leader in mid 2017, and experiencing a litany of setbacks by late 2019 through to early 2020. We address the role played by JUUL in the ongoing epidemic of youth vaping. We also feature competing views on the public health impact of JUUL use (in particular), and e-cig vaping (in general). We further highlight the latest trends in youth vaping and sales records for JUUL and tobacco cigarettes. In view of the ongoing pandemic of COVID-19, we briefly summarize the existing evidence on the relationship between vaping and smoking and the prevalence, disease course, and clinical outcomes of COVID-19.

Cardiorespiratory and Immunologic Effects of Electronic Cigarettes

PURPOSE OF REVIEW

Although e-cigarettes have become popular, especially among youth, the health effects associated with e-cigarette use remain unclear. This review discusses current evidence relating to the cardiovascular, pulmonary, and immunological effects of e-cigarettes.

RECENT FINDINGS

The use of e-cigarettes by healthy adults has been shown to increase blood pressure, heart rate, and arterial stiffness, as well as resistance to air flow in lungs. Inhalation of e-cigarette aerosol has been shown to elicit immune responses and increase the production of immunomodulatory cytokines in young tobacco-naïve individuals. In animal models, long-term exposure to e-cigarettes leads to marked changes in lung architecture, dysregulation of immune genes, and low-grade inflammation. Exposure to e-cigarette aerosols in mice has been shown to induce DNA damage, inhibit DNA repair, and promote carcinogenesis. Chronic exposure to e-cigarettes has also been reported to result in the accumulation of lipid-laden macrophages in the lung and dysregulation of lipid metabolism and transport in mice. Although, the genotoxic and inflammatory effects of e-cigarettes are milder than those of combustible cigarettes, some of the cardiorespiratory effects of the two insults are comparable. The toxicity of e-cigarettes has been variably linked to nicotine, as well as other e-cigarette constituents, operating conditions, and use patterns.

SUMMARY

The use of e-cigarettes in humans is associated with significant adverse cardiorespiratory and immunological changes. Data from animal models and in vitro studies support the notion that long-term use of e-cigarettes may pose significant health risks.

Effects of e-cigarettes and vaping devices on cardiac and pulmonary physiology

E-cigarette aerosols are exceedingly different from conventional tobacco smoke, containing dozens of chemicals not found in cigarette smoke. It is highly likely that chronic use of e-cigarettes will induce pathological changes in both the heart and lungs. Here we review human and animal studies published to date and summarize the cardiopulmonary physiological changes caused by vaping. In terms of cardiac physiology, acute exposure to e-cigarette aerosols in human subjects led to increased blood pressure and heart rate, similar to traditional cigarettes. Chronic exposure to e-cigarette aerosols using animal models caused increased arterial stiffness, vascular endothelial changes, increased angiogenesis, cardiorenal fibrosis and increased atherosclerotic plaque formation. Pulmonary physiology is also affected by e-cigarette aerosol inhalation, with increased airway reactivity, airway obstruction, inflammation and emphysema. Research thus far demonstrates that the heart and lung undergo numerous changes in response to e-cigarette use, and disease development will depend on how those changes combine with both environmental and genetic factors. E-cigarettes have been advertised as a healthy alternative to cigarette smoking, and users are under the impression that vaping of e-cigarettes is harmless, but these claims that e-cigarettes are safer and healthier are not based on evidence. Data from both humans and animal models are consistent in demonstrating that vaping of e-cigarettes causes health effects both similar to and disparate from those of cigarette smoking. Further work is needed to define the long-term cardiopulmonary effects of e-cigarette use in humans.

Method Validation Approaches for Analysis of Constituents in ENDS

OBJECTIVE

We assessed how many peer-reviewed publications reporting chemical quantities and/or yields from electronic nicotine delivery systems (ENDS) have included adequate method validation characteristics in the publication for appropriate interpretation of data quality for informing tobacco regulatory science.

METHODS

We searched 5 databases (Web of Knowledge, PubMed, SciFinder, Embase, EBSCOhost) for ENDS publications between January 2007 and September 2018. Of the 283 publications screened, 173 publications were relevant for analysis. We identified the publications that report a certain degree of control in data quality, ie, the publications that report marginally validated methods (MVMs). MVMs refer to the methods that: (1) report 3 or more International Conference on Harmonisation (ICH) method validation characteristics, (2) state the method was validated, (3) cite their own previous publication(s) that report MVMs, or (4) use a method within the accreditation scope of an accredited laboratory.

RESULTS

Overall, 97 publications (56%) report MVMs in their studies. This percentage also reflects the publication distribution for the majority of the 28 chemicals measured by MVMs.

CONCLUSIONS

This study highlights the need for reporting sufficient validation characteristics following appropriate guidance to ensure the accuracy and reliability of the published analytical data for proper data interpretations that may support policy.

A Qualitative Exploration of Consumers' Perceived Impacts, Behavioural Reactions, and Future Reflections of the EU Tobacco Products Directive (2017) as Applied to Electronic Cigarettes

BACKGROUND

Electronic cigarette regulations included in the Tobacco Products Directive (TPD), Article 20, implemented in Europe by May 2017, aimed to improve safety for e-cigarette consumers, and prevent uptake among non-smokers, particularly young people. Before implementation, there were significant concerns from consumers, industry, and some in the scientific community about the potential negative impact of the TPD on people using e-cigarettes to remain abstinent from smoking. To date, there is limited evidence on how the TPD has affected consumers. This study aimed to add insight into how consumers perceived and experienced the regulations.

METHODS

Qualitative data, collected between March 2018 and March 2019, relating to participant views of the TPD were extracted from 160 interviews/extended surveys of e-cigarette consumers as part of a wider study into e-cigarette use trajectories (ECtra study). Data were thematically analysed.

RESULTS

Awareness of the TPD among consumers was not universal. Participants' smoking behaviour did not appear to be influenced by the legislation. Participants were reassured by manufacturing regulations and requirements for ingredients labels. Participants responded negatively to changes perceived to cause inconvenience and extra plastic waste. The product restrictions prompted some participants to purchase non-compliant products illegally, potentially putting their safety at risk.

CONCLUSIONS

E-cigarette regulation should focus on ensuring product safety. Raising awareness of the TPD among consumers and smokers could be beneficial.

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.

Electronic nicotine delivery system design and aerosol toxicants: A systematic review

BACKGROUND

Electronic nicotine delivery systems (ENDS; e-cigarettes), consisting of a battery, heating element and e-liquid, have evolved significantly with wide variation in design, components, operating powers, and chemical constituents. Generated aerosols have been reported to contain potentially toxic substances. We conducted a systematic review to assess what is known about the presence of toxicants in ENDS aerosols in order to inform how system design could mitigate risk.

METHODS

Articles reporting on or evaluating design characteristics of ENDS and aerosol constituents were included and summarized.

RESULTS

The search identified 2,305 articles, of which 92 were included after full-text review. Findings were grouped into 6 major categories of potentially harmful chemicals: carbonyls, volatile organic chemicals, trace elements, reactive oxygen species and free radicals, polycyclic aromatic hydrocarbons, and tobacco-specific nitrosamines. In general, higher concentrations of aerosol toxicants are associated with increased power or voltage. Aerosol toxicants are also associated with e-liquid flavoring agents existing as primary ingredients or as products of thermal degradation.

CONCLUSIONS

Improved ENDS design can reduce toxicant levels. Additional research is needed to develop a framework for optimizing system characteristics to minimize exposure, especially with respect to heating power and e-liquids. Both manufacturers and regulatory agencies have roles in reducing toxicants and potential health risks from ENDS.

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.

A Procedure to Standardize Puff Topography During Evaluations of Acute Tobacco or Electronic Cigarette Exposure

INTRODUCTION

Documenting factors that influence differential sensitivity to acutely inhaled nicotine products requires carefully controlling the amount of exposure (dose), and thus a procedure by which to control such exposure.

METHODS

We evaluated consistency of puff volume from intermittent acute exposures to smoked tobacco cigarettes (study 1, n = 45, plus a comparison study of uninstructed use with n = 59) and to vaped electronic cigarettes (e-cigarettes; study 2, n = 27 naive to e-cigarettes) in adult-dependent smokers. All in primary studies 1 and 2 participated in research administering different nicotine levels in each product under blind conditions, one per session using within-subject designs. In both studies, participants followed an automated instructional procedure on a computer monitor standardizing the timing and amount of exposure to each product during a given trial, with four trials per session, each separated by 20 minutes. Puff volume per trial via Clinical Research Support System (CReSS) was the primary dependent measure to determine consistency across trials via intraclass correlation coefficients (ICCs).

RESULTS

Control over topography with both inhaled products was demonstrated by highly significant ICCs for puff volume across trials. Instructed control with own brand was generally better in study 1 than with uninstructed smoking in the comparison sample, as expected. As intended, reliability of puff volume generally did not differ by menthol preference or sex in either study, but ICCs in study 2 tended to be lower for some men using the placebo e-cigarette.

CONCLUSIONS

This instructional procedure may substantially improve control over amounts of acute exposure to tobacco or e-cigarette use.

IMPLICATIONS

Control over topography in studies of acute exposure to these inhaled products can potentially aid validity of research into differential sensitivity to use, so findings can be attributed to factors of interest and not to variable exposure. Our procedure minimized variability in exposure to the same product and between moderate nicotine products, but remaining differences suggest that compensation for very low or no nicotine commercial products may be difficult to totally eliminate with these instructions alone. Further study is needed to determine this procedure's utility with other inhaled products among experienced users and when comparing different products in between-groups analyses.

Daily exposure to formaldehyde and acetaldehyde and potential health risk associated with use of high and low nicotine e-liquid concentrations

Recent evidence suggests that e-cigarette users tend to change their puffing behaviors when using e-liquids with reduced nicotine concentrations by taking longer and more frequent puffs. Using puffing regimens modelled on puffing topography data from 19 experienced e-cigarette users who switched between 18 and 6 mg/mL e-liquids with and without power adjustments, differences in daily exposure to carbonyl compounds and estimated changes in cancer risk were assessed by production of aerosols generated using a smoking machine and analyzed using gas and liquid chromatography. Significant differences across conditions were found for formaldehyde and acetaldehyde (p < 0.01). Switching from a higher to a lower nicotine concentration was associated with greater exposure regardless of whether power settings were fixed or adjustable which is likely due to increased liquid consumption under lower nicotine concentration settings. Daily exposure for formaldehyde and acetaldehyde was higher for 17/19 participants when using low (6 mg/mL) compared with high (18 mg/mL) nicotine e-liquid concentration when power was fixed. When power adjustments were permitted, formaldehyde and acetaldehyde levels were higher respectively for 16/19 and 14/19 participants with the use of 6 compared with 18 mg/mL nicotine e-liquid.

Effects of Electronic Cigarettes on Indoor Air Quality and Health

With the rapid increase in electronic cigarette (e-cig) users worldwide, secondhand exposure to e-cig aerosols has become a serious public health concern. We summarize the evidence on the effects of e-cigs on indoor air quality, chemical compositions of mainstream and secondhand e-cig aerosols, and associated respiratory and cardiovascular effects. The use of e-cigs in indoor environments leads to high levels of fine and ultrafine particles similar to tobacco cigarettes (t-cigs). Concentrations of chemical compounds in e-cig aerosols are generally lower than those in t-cig smoke, but a substantial amount of vaporized propylene glycol, vegetable glycerin, nicotine, and toxic substances, such as aldehydes and heavy metals, has been reported. Exposures to mainstream e-cig aerosols have biologic effects but only limited evidence shows adverse respiratory and cardiovascular effects in humans. Long-term studies are needed to better understand the dosimetry and health effects of exposures to secondhand e-cig aerosols.

Effects of propylene glycol, vegetable glycerin, and nicotine on emissions and dynamics of electronic cigarette aerosols

An electronic cigarette (e-cig) generates aerosols by vaporizing the e-liquid, which mainly consists of propylene glycol (PG), vegetable glycerin (VG), and nicotine. Understanding the effects of e-liquid main compositions on e-cig aerosols is important for exposure assessment. This study investigated how the PG/VG ratio and nicotine content affect e-cig aerosol emissions and dynamics. A tank-based e-cig device with 10 different flavorless e-liquid mixtures (e.g., PG/VG ratios of 0/100, 10/90, 30/70, 50/50, and 100/0 with 0.0% or 2.4% nicotine) was used to puff aerosols into a 0.46 m³ stainless steel chamber for 0.5 h. Real-time measurements of particle number concentration (PNC), fine particulate matter (PM_2.5), and particle size distributions were conducted continuously throughout the puffing and the following 2-h decay period. During the decay period, particle loss rates were determined by a first-order log-linear regression and used to calculate the emission factor. The addition of nicotine in the e-liquid significantly decreased the particle number emission factor by 33%. The PM_2.5 emission factor significantly decreased with greater PG content in the e-liquid. For nicotine-free e-liquids, increasing the PG/VG ratio resulted in increased particle loss rates measured by PNC and PM_2.5. This pattern was not observed with nicotine in the e-liquids. The particle loss rates, however, were significantly different with and without nicotine especially when the PG/VG ratios were greater than 30/70. Compared with nonvolatile diethyl-hexyl subacute (DEHS) aerosols, e-cig particle concentration decayed faster inside the chamber, presumably due to evaporation. These results have potential implications for assessing human exposure to e-cig aerosols.

Persistent Severe Fixed Airways Obstruction in a High-Dosing E-cigarette User

Electronic Nicotine Delivery Systems (ENDS), commonly referred to as "e-cigs," were first introduced in the United States in 2007. Since then, their use has grown substantially, with the largest market among adolescents and young adults. ENDS are often perceived by the public as safe alternatives to traditional cigarettes and as aids in smoking cessation. Little is known about inhalational hazards of e-cigs. We describe the case of a 45-year-old man who developed acute respiratory symptoms associated with onset of severe fixed airways obstruction 9 months after he quit traditional cigarettes and began high-dose vaping. Lung biopsy showed respiratory bronchiolitis. Analysis of his heated e-cigarette solution identified a mixture containing vanillin, aldehydes, alcohols and other chemicals, the inhalation effects of which have not been well-studied. This case report adds to the growing literature describing potentially severe lung health effects of vaping and provides a framework for taking a clinical vaping history so that the health consequences of e-cigarettes may be better understood.

Latent Class Analysis of E-cigarette Use Sessions in Their Natural Environments

BACKGROUND

Delivery of nicotine and substances from electronic nicotine delivery systems, or e-cigarettes, depends in part on how users puff on the devices. Little is known about variation in puffing behavior to inform testing protocols or understand whether puffing behaviors result in increased exposure to emissions.

METHODS

We analyzed puff topography data collected using a wireless portable use monitor (wPUM) continuously over 2 weeks among 34 current second-generation e-cigarette users in their everyday lives. For each puff, the wPUM recorded date, time, duration, volume, flow rate, and inter-puff interval.

RESULTS

We defined use session and classes at the session level using multilevel latent profile analysis, resulting in two session classes and three person types. Session class 1 ("light") was characterized by 14.7 puffs per session (PPS), low puff volume (59.9 ml), flow rate (28.7 ml/s), and puff duration (202.7 s × 100). Session class 2 ("heavy") was characterized by 16.7 PPS with a high puff volume (290.9 ml), flow rate (71.5 ml/s), and puff duration (441.1 s × 100). Person class 1 had almost exclusively "light" sessions (98.0%), whereas person class 2 had a majority of "heavy" sessions (60.7%) and person class 3 had a majority of "light" sessions (75.3%) but some "heavy" sessions (24.7%).

CONCLUSION

Results suggest there are different session topography patterns among e-cigarette users. Further assessment is needed to determine whether some users have increased exposure to constituents and/or health risks because of e-cigarettes.

IMPLICATIONS

Our study examines topography characteristics in a users' natural setting to identify two classes of e-cigarette session behavior and three classes of users. These results suggest that it is important for studies on the health effects of e-cigarettes to take variation in user topography into account. It is crucial to accurately understand the topography profiles of session and user types to determine whether some users are at greater exposure to harmful or potentially harmful constituents and risks from e-cigarettes as they are used by consumers.

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.

A randomised, open-label, cross-over clinical study to evaluate the pharmacokinetic profiles of cigarettes and e-cigarettes with nicotine salt formulations in US adult smokers

E-cigarettes containing 'nicotine salts' aim to increase smoker's satisfaction by improving blood nicotine delivery and other sensory properties. Here, we evaluated the pharmacokinetic profiles and subjective effects of nicotine from two e-cigarette device platforms with varying concentrations of nicotine lactate (nicotine salt) e-liquid relative to conventional cigarettes. A randomised, open-label, cross-over clinical study was conducted in 15 healthy US adult smokers. Five different e-cigarette products were evaluated consecutively on different days after use of own brand conventional cigarette. Plasma nicotine pharmacokinetics, subjective effects, and tolerability were assessed following controlled use of the products. The rate of nicotine absorption into the bloodstream was comparable from all e-cigarettes tested and was as rapid as that for conventional cigarette. However, in all cases, nicotine delivery did not exceed that of the conventional cigarette. The pharmacokinetic profiles of nicotine salt emissions were also dependent upon the properties of the e-cigarette device. Subjective scores were numerically highest after smoking a conventional cigarette followed by the myblu 40-mg nicotine salt formulation. The rise in nicotine blood levels following use of all the tested e-cigarettes was quantified as 'a little' to 'modestly' satisfying at relieving the desire to smoke. All products were well tolerated with no notable adverse events reported. These results demonstrate that, while delivering less nicotine than a conventional cigarette, the use of nicotine salts in e-cigarettes enables cigarette-like pulmonary delivery of nicotine that reduces desire to smoke.

[Exposure of vapers to formaldehyde and acrolein: A systematic review]

Although recognized as less dangerous than conventional cigarettes, the toxicity of the electronic cigarette vapor's toxicity remains to be fully assessed. This review explores vapers' exposition to formaldehyde and acrolein.

METHOD

Systematic PubMed search for reports regarding formaldehyde or acrolein or their metabolites in electronic cigarette vapor, in vapers, or in ambient air.

RESULTS

Fifty-two publications were selected. Found in almost all studies on vaper, formaldehyde is 8 times out of 11 - and acrolein constantly - in lower amounts than those found in conventional cigarettes. Acrolein's metabolite is found in all studies in vapers. The concentrations of formaldehyde and/or acrolein generated during vapor production may be affected by the characteristics of the E-liquid, voltage, vaping topography, and by the flavor additives.

CONCLUSION

In the current state of knowledge, we must continue to support and help smokers to quit smoking, and for those who are engaged in a harm reduction approach, to minimize the duration of their electronic cigarette use.

Heated Tobacco Products: Volatile Emissions and Their Predicted Impact on Indoor Air Quality

This study characterized emissions from IQOS, a heated tobacco product promoted as a less harmful alternative to cigarettes. Consumable tobacco plugs were analyzed by headspace GC/MS to assess the influence of heating temperature on the emission profile. Yields of major chemical constituents increased from 4.1 mg per unit at 180 °C to 6.2 mg at 200 °C, and 10.5 mg at 220 °C. The Health Canada Intense smoking regime was used to operate IQOS in an environmental chamber, quantifying 33 volatile organic compounds in mainstream and sidestream emissions. Aldehydes, nitrogenated species, and aromatic species were found, along with other harmful and potentially harmful compounds. Compared with combustion cigarettes, IQOS yields were in most cases 1-2 orders of magnitude lower. However, yields were closer to, and sometimes higher than electronic cigarettes. Predicted users' daily average intake of benzene, formaldehyde, acetaldehyde and acrolein were 39 μg, 32 μg, 2.2 mg and 71 μg, respectively. Indoor air concentrations were estimated for commonly encountered scenarios, with acrolein levels of concern (over 0.35 μg m-3) derived from IQOS used in homes and public spaces. Heated tobacco products are a weaker indoor pollution source than conventional cigarettes, but their impacts are neither negligible nor yet fully understood.

New and Emerging Tobacco Products and the Nicotine Endgame: The Role of Robust Regulation and Comprehensive Tobacco Control and Prevention: A Presidential Advisory From the American Heart Association

The advent of new tobacco products such as electronic cigarettes and the dramatic rise in their use, especially by adolescents and young adults, are significant public health concerns. Electronic cigarettes have become the most popular tobacco products for youth and adolescents in the United States and are attracting youth to new avenues for nicotine addiction. Although these products may have benefit by helping some smokers quit or to move to a less harmful product, the long-term health effects of these products and the net public health effect associated with their use remain unclear and widely debated. There is increasing concern that the use of newer tobacco products may catalyze transition to the use of other tobacco products or recreational drugs, particularly in young adults. Therefore, there is urgent need for robust US Food and Drug Administration regulation of all tobacco products to avoid the significant economic and population health consequences of continued tobacco use. Although the American Heart Association acknowledges that the ultimate endgame would be an end to all tobacco and nicotine addiction in the United States, it supports first minimizing the use of all combustible tobacco products while ensuring that other products do not addict the next generation of youth and adolescents. The endgame strategy needs to be coordinated with the long-standing, evidence-based tobacco control strategies that have significantly reduced tobacco use and initiation in the United States.

Electronic cigarette substitution in the experimental tobacco marketplace: A review

The evolution of science derives, in part, from the development and use of new methods and techniques. Here, we discuss one development that may have impact on the understanding of tobacco regulatory science: namely, the application of behavioral economics to the complex tobacco marketplace. The purpose of this paper is to review studies that examine conditions impacting the degree to which electronic nicotine delivery system (ENDS) products substitute for conventional cigarettes in the Experimental Tobacco Marketplace (ETM). Collectively, the following factors constitute the current experimental understanding of conditions that will affect ENDS use and substitution for conventional cigarettes: increasing the base price of conventional cigarettes, increasing taxation of conventional cigarettes, subsidizing the price of ENDS products, increasing ENDS nicotine strength, and providing narratives that illustrate the potential health benefits of ENDS consumption in lieu of conventional cigarettes. Each of these factors are likely moderated by consumer characteristics, which include prior ENDS use, ENDS use risk perception, and gender. Overall, the ETM provides a unique method to explore and identify the conditions by which various nicotine products may interact with one another that mimics the real world. In addition, the ETM permits the efficacy of a broad range of potential nicotine policies and regulations to be measured prior to governmental implementation.

A framework to investigate the impact of topography and product characteristics on electronic cigarette emissions

SIGNIFICANCE

Protocols for testing and reporting emissions of Harmful and Potentially Harmful Constituents (HPHCs) from electronic cigarettes (e-cigs) are lacking. The premise of this study is that multi-path relationships may be developed to describe interactions between product characteristics, use behavior and emissions to develop appropriate protocols for tobacco product regulatory compliance testing.

METHODS

This study proposes a framework consisting of three component terms: HPHC mass concentration, HPHC mass ratio and total particulate mass (TPM) concentration. The framework informs experiments to investigate dependence of aerosol emissions from five electronic cigarettes spanning several design generations and three e-liquids for six repeated trials at each of ten flow conditions.

RESULTS

Results are reported for TPM concentration as a function of flow conditions spanning the range of natural environment topography observed in prior studies. An empirical correlation describing TPM concentration as a function of flow conditions and coil power setting (6, 7.5 and 10 watts) for the Innokin iTaste MVP 2.0 vaporizer with Innokin iClear 30 dual coil tank is presented. Additional results document the impact of flow conditions and wick and coil design on TPM concentration through comparison of the Innokin iClear 30 (upper coil, capillary action wick) and the Innokin iClear X.I (lower coil, gravity fed wick) operated at 7.5 watts. The impact of e-liquid on TPM concentration is illustrated by comparing emissions from an NJOY Vape Pen filled with AVAIL Arctic Blast, Tobacco Row, and Mardi Gras e-liquids. TPM concentration is shown to depend upon flow conditions across a range of e-cigarette product designs including cig-a-like, pen-style, box-mod and emergent disposable-cartridge style devices.

CONCLUSIONS

A framework provides a foundation for reporting emissions across a variety of e-cigs, e-liquids and research laboratories. The study demonstrates TPM concentration is a function of topography behavior (i.e. puff flow rate and puff duration) for varying device operating power and product characteristics.

'Real-world' compensatory behaviour with low nicotine concentration e-liquid: subjective effects and nicotine, acrolein and formaldehyde exposure

AIMS

To compare the effects of (i) high versus low nicotine concentration e-liquid, (ii) fixed versus adjustable power and (iii) the interaction between the two on: (a) vaping behaviour, (b) subjective effects, (c) nicotine intake and (d) exposure to acrolein and formaldehyde in e-cigarette users vaping in their everyday setting.

DESIGN

Counterbalanced, repeated measures with four conditions: (i) low nicotine (6 mg/ml)/fixed power; (ii) low nicotine/adjustable power; (iii) high nicotine (18 mg/ml)/fixed power; and (iv) high nicotine/adjustable power.

SETTING

London and the South East, England.

PARTICIPANTS

Twenty experienced e-cigarette users (recruited between September 2016 and February 2017) vaped ad libitum using an eVic Supreme™ with a 'Nautilus Aspire' tank over 4 weeks (1 week per condition).

MEASUREMENTS

Puffing patterns [daily puff number (PN), puff duration (PD), interpuff interval (IPI)], ml of e-liquid consumed, changes to power (where permitted) and subjective effects (urge to vape, nicotine withdrawal symptoms) were measured in each condition. Nicotine intake was measured via salivary cotinine. 3-Hydroxypropylmercapturic acid (3-HPMA), a metabolite of the toxicant acrolein, and formate, a metabolite of the carcinogen formaldehyde, were measured in urine.

FINDINGS

There was a significant nicotine concentration × power interaction for PD (P < 0.01). PD was longer with low nicotine/fixed power compared with (i) high nicotine/fixed power (P < 0.001) and (ii) low nicotine/adjustable power (P < 0.01). PN and liquid consumed were higher in the low versus high nicotine condition (main effect of nicotine, P < 0.05). Urge to vape and withdrawal symptoms were lower, and nicotine intake was higher, in the high nicotine condition (main effects of nicotine: P < 0.01). While acrolein levels did not differ, there was a significant nicotine × power interaction for formaldehyde (P < 0.05).

CONCLUSIONS

Use of a lower nicotine concentration e-liquid may be associated with compensatory behaviour (e.g. higher number and duration of puffs) and increases in negative affect, urge to vape and formaldehyde exposure.

Differential Effects of E-Cigarette on Microvascular Endothelial Function, Arterial Stiffness and Oxidative Stress: A Randomized Crossover Trial

Propylene glycol and glycerol are electronic cigarettes vehicles allowing liquid vaporization and nicotine transport. The respective effects of these different constituents on the cardiovascular system are unknown. We assessed the differential effects of vehicles (propylene glycol and glycerol) and nicotine on microcirculatory function, arterial stiffness, hemodynamic parameters and oxidative stress. Twenty-five tobacco smokers were exposed to vaping with and without nicotine, and sham vaping, in a randomized, single blind, 3-period crossover design study. Neither sham-vaping nor vaping in the absence of nicotine resulted in modifications of cardiovascular parameters or oxidative stress. In contrast, vaping with nicotine: 1) impaired acetylcholine mediated vasodilation (mean ± standard error mean) (area under curve, perfusion unit (PU), 3385 ± 27PU to 2271 ± 27PU, p < 0.0001); 2) increased indices of arterial stiffness, namely augmentation index corrected for heart rhythm (−3.5 ± 1.5% to 1.9 ± 2.3%; p = 0.013) and pulse wave velocity (4.9 ± 0.1 m.s⁻¹ to 5.3 ± 0^.1 m.s⁻¹; p < 0.0001); 3) increased systolic and diastolic blood pressures as well as heart rate (all p < 0.0001) and finally; 4) raised plasma myeloperoxidase (median [interquartile range]) (13.6 ng.ml⁻¹ [10–17.7] to 18.9 ng.ml⁻¹ [12.2–54.4], p = 0.005). Our findings demonstrated that high temperature e-cigarette vehicle vaporization does not alter micro- and macro-vascular function, and oxidative stress, and that these effects are solely attributable to nicotine.

Experimental tobacco marketplace: substitutability of e-cigarette liquid for cigarettes as a function of nicotine strength

BACKGROUND

The experimental tobacco marketplace (ETM) provides a method to estimate, prior to implementation, the effects of new products or policies on purchasing across various products in a complex tobacco marketplace. We used the ETM to examine the relationship between nicotine strength and substitutability of alternative products for cigarettes to contribute to the literature on regulation of e-liquid nicotine strength.

METHODS

The present study contained four sampling and four ETM purchasing sessions. During sampling sessions, participants were provided 1 of 4 e-liquid strengths (randomised) to sample for 2 days followed by an ETM purchasing session. The nicotine strength sampled in the 2 days prior to an ETM session was the same strength available for purchase in the next ETM. Each participant sampled and could purchase 0 mg/mL, 6 mg/mL, 12 mg/mL and 24 mg/mL e-liquid, among other products, during the study.

RESULTS

Cigarette demand was unaltered across e-liquid strength. E-liquid was the only product to substitute for cigarettes across more than one e-liquid strength. Substitutability increased as a function of e-liquid strength, with the 24 mg/mL displaying the greatest substitutability of all products.

CONCLUSIONS

The present study found that e-liquid substitutability increased with nicotine strength, at least up to 24 mg/mL e-liquid. However, the effects of e-liquid nicotine strength on cigarette purchasing were marginal and total nicotine purchased increased as e-liquid nicotine strength increased.

Carbonyl Emissions in E-cigarette Aerosol: A Systematic Review and Methodological Considerations

Carbonyl emissions from tobacco cigarettes represent a substantial health risk contributing to smoking-related morbidity and mortality. As expected, this is an important research topic for tobacco harm reduction products, in an attempt to compare the relative risk of these products compared to tobacco cigarettes. In this study, a systematic review of the literature available on PubMed was performed analyzing the studies evaluating carbonyl emissions from e-cigarettes. A total of 32 studies were identified and presented. We identified a large diversity of methodologies, with substantial discrepancies in puffing patterns, aerosol collection and analytical methods as well as reported units of measurements. Such discrepancies make comparisons difficult, and in some cases the accuracy of the findings cannot be determined. Importantly, control for the generation of dry puffs was not performed in the vast majority of studies, particularly in studies using variable power devices, which could result in testing conditions and reported carbonyl levels that have no clinical relevance or context. Some studies have been replicated, verifying the presence of dry puff conditions. Whenever realistic use conditions were ensured, carbonyl emissions from e-cigarettes were substantially lower than tobacco cigarette smoke, while newer generation (bottom-coil, cotton wick) atomizers appeared to emit minimal levels of carbonyls with questionable clinical significance in terms of health risk. However, extremely high levels of carbonyl emissions were reported in some studies, and all these studies need to be replicated because of potentially important health implications.