Electronic Cigarettes: A Pro-Con Review of the Current Literature

Comparative study of bisphenols in e-cigarette liquids: Evaluating fabric phase sorptive extraction, ultrasound-assisted membrane extraction, and solid phase extraction techniques

To address the under-researched risk of bisphenols (BPs) in e-cigarette liquids, comprehensive studies have been conducted to propose optimum sample preparation and analysis methods. To determine twelve BPs in refill liquids for e-cigarettes, three sample preparation methods based on distinct operational and working principles were employed. These included fabric phase sorptive extraction (FPSE), ultrasound-assisted solvent extraction of porous membrane-packed samples (UASE-PMS) and solid phase extraction (SPE) utilizing molecularly imprinted polymers (MIPs) technology. Each extraction method was combined with ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). Key parameters of FPSE and UASE-PMS procedures were optimized. This optimization included selection of the FPSE membrane types, durations of extraction and the choice solvents. Comprehensive validation was conducted, demonstrating linearity across a range from 2 to 60 ng/mL for all BPs (BPS, BPA, BPF, BPE, BPB, BPC, BPZ, BPFL, BPBP, BPP, BPG and BPM). Determination coefficients were above 0.9913, signifying linear relationship. The limits of detection (LODs) were established below 0.90 ng/mL, while the limits of quantification (LOQs) were lower than 2.5 ng/mL. Notably, the method based on UASE-PMS was successfully applied to the analysis of refill liquids for e-cigarettes samples. A comparative analysis of the methods highlighted variances in precision, accuracy, and applicable aspects, such as adjustment of parameters, sample preparation time, cost, handling, availability and possible limitations. Three methods have been identified as suitable for analysing BPs in e-cigarette refill liquids, highlighting the necessity to examine their presence in these products.

Pharmacokinetic analysis of nicotine and its metabolites (cotinine and trans-3'-hydroxycotinine) in male Sprague-Dawley rats following nose-only inhalation, oral gavage, and intravenous infusion of nicotine

Nicotine is an alkaloid found in tobacco. Human exposure to nicotine primarily occurs through the use of tobacco products. To date, limited nicotine pharmacokinetic data in animals have been reported. This study exposed male Sprague-Dawley rats to vehicle (and/or air) or 4 doses of nicotine via nose-only inhalation (INH), oral gavage (PO), and intravenous (IV) infusion. Plasma, 6 tissues (brain, heart, lung, liver, kidney, and muscle), and urine were collected at multiple timepoints from 5 min to 48 h post-dose. The concentrations of nicotine, cotinine, and trans-3'-hydroxycotinine (3-OH-cotinine) were determined, and the pharmacokinetic profiles were compared among the 4 doses for each route. The results indicated that after single nicotine dose, nicotine bioavailability was 53% via PO. Across all the administration routes and doses, nicotine was quickly distributed to all 6 tissues; kidney had the highest nicotine and cotinine levels, and the lung had the highest 3-OH-cotinine levels; nicotine was metabolized extensively to cotinine and cotinine was metabolized to a lesser extent to 3-OH-cotinine; the elimination of plasma nicotine, cotinine, and 3-OH-cotinine followed first-order kinetics; plasma nicotine had a shorter half-life than cotinine or 3-OH-cotinine; the half-lives of plasma nicotine, cotinine, and 3-OH-cotinine were dose- and route-independent; and nicotine and cotinine were major urinary excretions followed by 3-OH-cotinine. Nicotine, cotinine, and 3-OH-cotinine levels in plasma, tissues, and urine exhibited dose-dependent increases. These study findings improve our understanding of the pharmacokinetics of nicotine, cotinine, and 3-OH-cotinine across different routes of exposure.

A Review of the Toxicity of Ingredients in e-Cigarettes, Including Those Ingredients Having the FDA's "Generally Recognized as Safe (GRAS)" Regulatory Status for Use in Food

Some firms and marketers of electronic cigarettes (e-cigarettes; a type of electronic nicotine delivery system (ENDS)) and refill liquids (e-liquids) have made claims about the safety of ingredients used in their products based on the term "GRAS or Generally Recognized As Safe" (GRAS). However, GRAS is a provision within the definition of a food additive under section 201(s) (21 U.S.C. 321(s)) of the U.S. Federal Food Drug and Cosmetic Act (FD&C Act). Food additives and GRAS substances are by the FD&C Act definition intended for use in food, thus safety is based on oral consumption; the term GRAS cannot serve as an indicator of the toxicity of e-cigarette ingredients when aerosolized and inhaled (ie, vaped). There is no legal or scientific support for labeling e-cigarette product ingredients as "GRAS." This review discusses our concerns with the GRAS provision being applied to e-cigarette products and provides examples of chemical compounds that have been used as food ingredients but have been shown to lead to adverse health effects when inhaled. The review provides scientific insight into the toxicological evaluation of e-liquid ingredients and their aerosols to help determine the potential respiratory risks associated with their use in e-cigarettes.

Prevalence of Electronic Cigarette Use Among Female Residents of Al-Ahsa, Kingdom of Saudi Arabia: A Cross-Sectional Study

Background Electronic cigarettes (e-cigarettes) have gained considerable popularity on a global scale, with an increasing prevalence among younger adults. The objective of this study was to investigate the prevalence, patterns, and determinants of e-cigarette use among women in Al-Ahsa, Saudi Arabia. Methodology A cross-sectional study was conducted between October 2023 and July 2024 involving 491 adult female participants. The data were collected using a structured questionnaire and subsequently analyzed using SPSS Version 26.0 (IBM Corp., Armonk, NY, USA). Descriptive and inferential statistics, including chi-square tests, were employed to assess relationships between e-cigarette use and various independent variables. Results The prevalence of e-cigarette use among participants was 17.5%. Significant factors associated with e-cigarette use included age (highest among women aged 21 to 30 years, p = 0.038), unemployment (p = 0.011), perceived poor health (p = 0.002), and having friends or family members who use e-cigarettes (p = 0.001). The primary reasons for using e-cigarettes were influence from friends (70.9%) and family members (54.7%), curiosity (33.7%), and appealing flavors (30.2%). A considerable proportion of users reported experiencing dependence and difficulty quitting. Conclusions The prevalence of e-cigarette use among female residents of Al-Ahsa is influenced by a complex interplay of social, demographic, and perceptual factors. The findings underscore the necessity for comprehensive interventions targeting social environments and educational initiatives and addressing misconceptions about the potential risks of e-cigarettes.

Current perspective on e-cigarette use and respiratory outcomes: mechanisms and messaging

INTRODUCTION

There has been an increasing amount of research on the consequences of e-cigarette use for respiratory outcomes, which is significant for public health and respiratory medicine. We discuss recent findings and lay out implications for prevention and treatment.

AREAS COVERED

Based on literature searches using several databases (PubMed, Web of Science, Google Scholar) for keywords, including synonyms, 'e-cigarettes,' with 'pulmonary function,' 'oxidative stress,' and 'inflammation,' we review studies on acute effects of e-cigarette use for measures of pulmonary function and discuss selected laboratory studies on mechanisms of effect, focusing on processes with known relation to respiratory disease; oxidative stress and inflammation. We discuss available studies that have tested the effectiveness of communication strategies for prevention of e-cigarette use oriented to different audiences, including nonsmoking adolescents and adult smokers.

EXPERT OPINION

We conclude that the evidence presents a mixed picture. Evidence is found for adverse consequences of e-cigarette use on measures of lung function and two disease-related biological processes, sometimes but not always less than for cigarette smoking. How to best communicate these results to a complex audience of users, from younger susceptible adolescents to long-term adult smokers interested in quitting, is a question of significant interest and empirically validated communication strategies are greatly needed.

Investigation of the impact of thirdhand e-cigarette exposure on platelet function: A pre-clinical study

INTRODUCTION

The use of e-cigarettes (ECs) has reached unprecedented levels, due to a variety of reasons, including the misconception regarding their safety. Thus, there have been efforts to characterize the effects of EC exposure, including in the context of thirdhand EC (THEC) on a host of disorders, such as cardiovascular disease (CVD).

METHODS

To address this issue, we sought to characterize the effects of THEC on platelet function and thrombus formation, using a novel mouse exposure protocol that resembles real life scenarios. To assess these effects, a host of related in vivo (i.e. tail bleeding time, and ferric chloride injury induced thrombosis model) assays and in vitro platelet specific (e.g. aggregation, and dense granule secretion) investigative assays were conducted.

RESULTS

Our in vivo characterization demonstrated that THEC exposed mice exhibited a prothrombotic phenotype reflected by their shortened tail bleeding (THEC: 37 ± 15 seconds, versus clean air: 183 ± 56 s) and occlusion times (THEC: 188 ± 39 s, versus clean air: 519 ± 70 s), relative to those exposed to clean air. Importantly, we found no difference in the platelet counts between the THEC and clean air mice. As for the underlying mechanism, separate experiments revealed significantly enhanced platelet aggregation, dense and alpha granule secretion, as well as integrin/GPIIb-IIIa activation and phosphatidylserine exposure in response to thrombin and ADP agonist stimulation.

CONCLUSIONS

Taken together, these results provide evidence that THEC does have the capacity to increase the risk of thrombotic disease, which should increase awareness regarding its underappreciated negative health effects.

Evaluation of Cytotoxic and Genotoxic Effects in Buccal Mucosal Cells in Non-Smokers and Users of Traditional Combustible Tobacco Products and Non-Combustible Alternatives

AIMS/OBJECTIVES

The aim of this cross-sectional observational study was to investigate cytogenetic damage to the buccal mucosa in non-smokers and consumers of traditional combustible tobacco products and non-combustible alternatives.

METHODS

A total of 160 participants were divided into four groups according to the type of product used, including non-smokers, users of conventional combustible tobacco (cigarettes), heated tobacco, and electronic, tobacco-free vapor products (e-cigarettes). Buccal mucosa samples were analyzed using the micronucleus cytome assay to assess cytotoxic and genotoxic damage.

RESULTS

E-cigarette users showed significantly higher values for all tested parameters in the micronucleus test compared to non-smokers (p < 0.05). Similarly, users of tobacco heating products showed an increase in all parameters (p < 0.05), with the exception of the number of cells with micronuclei. Conventional cigarette smokers showed a notable increase in the number of binucleated cells and cells with karyorrhexis and karyolysis (p ≤ 0.05). When assessing the differences between users of traditional combustible tobacco products and non-combustible alternatives, these did not appear to be significant, except for e-cigarette users, who had significantly more cells with condensed chromatin (p ≤ 0.001), while users of tobacco heating products had more pyknotic cells (p ≤ 0.001).

CONCLUSION

The results of this study underscore the heightened occurrence of cytotoxic and genotoxic damage in users of both conventional combustible tobacco products and non-combustible alternatives compared to non-smokers, emphasizing the detrimental impact of these products on the oral mucosa.

Electronic cigarette use and cigarette smoking associated with inadequate sleep duration among U.S. young adults

OBJECTIVE

Nicotine use can influence inadequate sleep, but less is known about the associations of exclusive and dual use of electronic cigarettes (e-cigarettes) with combustible cigarettes in U.S. young adults. This study assessed the associations between current exclusive e-cigarette use, exclusive cigarette smoking, and dual e-cigarette and combustible cigarette use and inadequate sleep duration among U.S. young adults.

METHODS

We performed a secondary analysis of 2020 Behavioral Risk Factor Surveillance System (BRFSS) data including 13,978 U.S. young adults ages 18-24 years. Inadequate sleep duration was assessed categorically using the National Sleep Foundation's age-specific recommendations that define <7 h as inadequate sleep. Weighted logistic regression models were performed while adjusting for participants' sex, race/ethnicity, education level, annual household income level, body mass index, current physical activity, mental health status, disability status, current alcohol use, and current smokeless tobacco use.

RESULTS

Concerning use patterns, 11.8% of young adults were exclusive e-cigarette users, 4.7% were exclusive cigarette smokers, and 3.8% were dual e-cigarette and combustible cigarette users. Exclusive e-cigarette users (adjusted odds ratio [AOR] = 1.41, 95% confidence interval [CI] = 1.16-1.72), exclusive cigarette smokers (AOR = 1.63, 95%CI = 1.22-2.18), and dual product users (AOR = 2.03, 95%CI = 1.44-2.86) were at increased odds of having inadequate sleep duration compared to non-users, while adjusting for the covariates. Additionally, dual product users were at increased odds (AOR = 1.52, 95%CI = 1.06-2.19) of reporting inadequate sleep duration compared to exclusive e-cigarette users, while adjusting for the covariates.

CONCLUSIONS

Current e-cigarette and cigarette use may influence inadequate sleep among U.S. young adults. Tobacco cessation efforts may encourage increased sleep health.

Electronic Cigarette Harms: Aggregate Evidence Shows Damage to Biological Systems

Evidence of the harms of e-cigarettes has been unfolding slowly and has been documented in many reviews and reports worldwide. A narrative review of new evidence is presented since, as research has continued, newly aggregated evidence of the dangers of electronic cigarettes on the brain, heart, and lungs is vital to inform decisions on restricting the use of e-cigarettes. Several biomedical research databases were searched for electronic cigarette health effects, emphasizing reviews, systematic reviews, and meta-analyses. Over 50 review studies, primarily in 2022 and 2023, illustrate some of the latest information on e-cigarette harms. Results show studies of respiratory, neurological, and cardiovascular effects. Researchers call for expanding studies through new methods to elaborate on initial findings of multiple harms emerging in clinical investigations. Since the use of electronic cigarettes for adult cessation is not sanctioned in most countries, it is clear that health authorities see significant costs to the health of the general population if the promotion and use of electronic cigarettes occur worldwide. Regulatory action to control electronic cigarettes should consider the substantial evidence of electronic cigarette harm.

Effects of vaping on uptake and cessation of smoking: Longitudinal analysis in Aotearoa New Zealand adults

INTRODUCTION

Globally, the use of vapes, or e-cigarettes, is increasing. While vaping is less harmful than smoking and may help smokers to quit, there is also the possibility that vaping may lead to smoking. The current study aimed to determine the prevalence of vaping and smoking in Aotearoa New Zealand and explore longitudinal pathways between smoking status and vape use.

METHOD

Data related to smoking and vaping status was analysed from Times 10, 11 and 12 across 2018-2020 of the New Zealand Attitudes and Values study, a large, representative, multi-wave study of adults living in New Zealand. Weighted descriptive analyses were used to determine prevalence rates of vaping and smoking and a generalised linear modelling approach was used to examine the likelihood of changing to, or taking up, the other behaviour in the transition between time points.

RESULTS

Broadly, the prevalence of smoking was found to be decreasing over time while the prevalence of vaping was increasing. Despite these general trends, no differences were observed in the likelihood of transitioning from smoking to vaping or from vaping to smoking, indicating that either pathway was equally as likely.

DISCUSSION AND CONCLUSIONS

The current findings demonstrate that vaping appeared to be just as likely to have a gateway effect to smoking as it was to have a cessation effect. This highlights the need for greater consideration regarding vaping-related policies and restrictions.

Cigarettes, ENDS Use, and Chronic Obstructive Pulmonary Disease Incidence: A Prospective Longitudinal Study

INTRODUCTION

Understanding the relationship between ENDS use and chronic obstructive pulmonary disease (COPD) and other respiratory conditions is critical. However, most previous studies have not fully adjusted for cigarette smoking history.

METHODS

Using Waves 1-5 of the U.S. Population Assessment of Tobacco and Health study, the association between ENDS use and self-reported incident COPD was examined among adults aged 40+ years using discrete-time survival models. Current ENDS use was measured as a time-varying covariate, lagged by 1 wave, defined as established daily or some days of use. Multivariable models were adjusted for baseline demographics (age, sex, race/ethnicity, education), health characteristics (asthma, obesity, exposure to second-hand smoke), and smoking history (smoking status and cigarette pack years). Data were collected between 2013 and 2019, and the analysis was conducted in 2021-2022.

RESULTS

Incident COPD was self-reported by 925 respondents during the 5-year follow-up. Before adjusting for other covariates, time-varying ENDS use appeared to double COPD incidence risk (hazard ratio=1.98, 95% CI=1.44, 2.74). However, ENDS use was no longer associated with COPD (adjusted hazard ratio=1.10, 95% CI=0.78, 1.57) after adjusting for current cigarette smoking and cigarette pack years.

CONCLUSIONS

ENDS use did not significantly increase the risk of self-reported incident COPD over a 5-year period once current smoking status and cigarette pack years were included. Cigarette pack years, by contrast, remained associated with a net increase in COPD incidence risk. These findings highlight the importance of using prospective longitudinal data and adequately controlling for cigarette smoking history to assess the independent health effects of ENDS.

Characterization of an Electronic Nicotine Delivery System (ENDS) Aerosol Generation Platform to Determine Exposure Risks

Evaluating vaping parameters that influence electronic nicotine delivery system (ENDS) emission profiles and potentially hazardous exposure levels is essential to protecting human health. We developed an automated multi-channel ENDS aerosol generation system (EAGS) for characterizing size-resolved particle emissions across pod- and mod-type devices using real-time monitoring instruments, an exposure chamber, and vaping parameters including different ventilation rates, device type and age, e-liquid formulation, and atomizer setup. Results show the ENDS device type, e-liquid flavoring, and nicotine content can affect particle emissions. In general, pod-type devices have unimodal particle size distributions and higher number emissions, while mod-type devices have bimodal size distributions and higher mass emissions. For pod-type devices, later puff fractions emit lower aerosols, which is potentially associated with the change of coil resistance and power during ageing. For a mod-type device, an atomizer with a lower resistance coil and higher power generates larger particle emissions than an atomizer with a greater resistance coil and lower power. The unventilated scenario produces higher particle emission factors, except for particle mass emission from pod-type devices. The data provided herein indicate the EAGS can produce realistic and reproducible puff profiles of pod- and mod-type ENDS devices and therefore is a suitable platform for characterizing ENDS-associated exposure risks.

A Systematic Review of the Literature Examining the Effects of Cigarette Smoke and e-Cigarette Vapor on the Virulence of Human Pathogenic Bacteria

The bioactive chemicals in cigarette smoke (CS) and e-cigarette vapor (EV) may affect pathogenic bacteria in the nasopharyngeal microflora, which may have implications on the pathophysiology of respiratory infections in cigarette smokers and e-cigarette users. In this systematic review, we seek to synthesize the research evidence supporting this hypothesis. To address the central research question, "what is known from the published, peer-reviewed literature about the effects of cigarette smoke or e-cigarette vapor exposure on the physiology of human pathogenic bacteria?", we screened the PubMed®, Web of ScienceTM, and ScienceDirect databases for reports examining the virulence characteristics and gene expression in human pathogenic bacteria exposed to either CS or EV. The principal conclusion from our analysis is that exposure to either CS or EV induces the virulence of respiratory pathogenic bacteria in a strain-dependent manner, which may in turn facilitate respiratory infections in cigarette smokers and e-cigarette users. In addition, we present evidence that nicotine and reactive oxygen species are the main chemicals responsible for CS/EV-mediated alterations in bacterial physiology. We note limitations that this review does not examine reports describing the alterations in host respiratory physiology or nasopharyngeal dysbiosis caused by CS/EV exposure. Future research to determine whether CS/EV-mediated augmentation of bacterial virulence indeed plays a role in human respiratory tract infections is warranted.