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

Perceptions and usage of traditional cigarettes, electronic cigarettes, and waterpipes among young and middle-aged adults in Iraq: A descriptive study

Tobacco use poses significant public health concerns, linked to various mental and physical health outcomes. Iraq has a high prevalence of smoking, predominantly with traditional cigarettes, but there is also growing popularity of electronic cigarettes and waterpipes among younger and middle-aged adults. This study aims to explore the perceptions and usage of traditional cigarettes, electronic cigarettes, and waterpipes among this population in Iraq. A descriptive study was conducted among 402 young and middle-aged adults (50.25% females), aged between 18 and 45 years, with a mean age of 25.88 (SD = 7.27). For the data collection, an online questionnaire was developed utilizing distribution channels on common social networking platforms. The results showed that 41.79% of respondents have used traditional cigarettes, while 31.1% of participants reported that they use electronic cigarettes. Ninety-four per cent of respondents acknowledged that they use waterpipes. The results also indicated that a significant proportion believe that using electronic cigarettes is either much more harmful or more harmful than traditional cigarettes. Participants commonly perceived all three types of tobacco products as highly harmful, including secondhand smoke, addictive qualities, and popularity among peers. Additionally, significant differences in perceptions emerged between smokers and nonsmokers regarding electronic cigarettes and traditional cigarettes, although no such differences were observed for waterpipes. These findings contribute to understanding the attitudes toward different forms of tobacco use among respondents, highlighting the need for targeted interventions to address the perceived harm associated with tobacco products.

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

INTRODUCTION

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 (i.e., 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.

IMPLICATIONS

The rise in prevalence of e-cigarette use and emerging evidence of adverse effects, particularly on lung health, warrant assessing all aspects of e-cigarette toxicity. One development is manufacturers' stated or implied claims of the safety of using e-cigarette products containing ingredients determined to be "Generally Recognized As Safe" (GRAS) for use in food. Such claims, typically placed on e-cigarette product labels and used in marketing, are unfounded, as pointed out by the United States Food and Drug Administration (FDA)1 and the Flavor and Extract Manufacturers Association (FEMA)2. Assessment of inhalation health risks of all ingredients used in e-liquids, including those claimed to be GRAS, is warranted.

Sexual activity and respiratory disease: A systematic review

CONTEXT

Sex and gender are related concepts, but they have distinct meanings and implications. Respiratory diseases are a major driver of morbi-mortality. It is frequent that respirologists, primary care doctors, or other specialists, when dealing with respiratory patients, and aiming for a holistic management of their patients, they all skip any question or matter associated with sexual activity or behavior.

OBJECTIVES

To review how sexual activity is explored in respiratory patients.

METHODS

To conduct this review, we endorse PRISMA guidance for reporting systematic reviews, and also the sex and gender equity in research (SAGER) guidelines.

RESULTS

Compared to other conditions such as heart disease, mental disorders, Alzheimer's, or even COVID-19, to date there is no review focused on sexual activity and respiratory health and disease. Asthma, COPD and other respiratory patients can have their sexual activity and behaviors affected by their disease, but also limitations in sex might be the sentinel event of an incident respiratory disease. Asking on sexual desire and related sex issues should not be considered taboo in any respiratory consultation. Importantly, any marketed stereotypes on cigarettes after any sexual activity should be counteracted. Many clinical trials of respiratory drugs keep recruiting few or no women, so research on women's sexual desire and satisfaction lags behind that of men's. By using the available objective tools and validated questionnaires summarized in this review, these important domains of respiratory patients and their partners can be properly identified and managed.

CONCLUSIONS

Sexual activity, depending on age and individual specific conditions, is a fundamental driver of overall health, and therefore of lung health.

Comparative systematic review on the safety of e-cigarettes and conventional cigarettes

BACKGROUND

This systematic review evaluated the health risks of electronic cigarettes (e-cigarettes) compared to traditional cigarettes. It examines various studies and research on the subject to provide a comprehensive analysis of potential health risks associated with both smoking methods.

METHODS

The systematic review, incorporating searches in PubMed, Scopus, Web of Science, and the Cochrane Library up to July 2023, examines the results obtained in relevant studies, and provides a critical discussion of the results.

RESULTS

E-cigarettes exhibit reduced exposure to harmful toxins compared to traditional cigarettes.

CONCLUSION

However, concerns persist regarding respiratory irritation and potential health risks, especially among youth, emphasizing the need for comprehensive, long-term research and protective legislation.

Zebrafish (Danio rerio) as a Model for the Study of Developmental and Cardiovascular Toxicity of Electronic Cigarettes

The increasing popularity of electronic cigarettes (e-cigarettes) as an alternative to conventional tobacco products has raised concerns regarding their potential adverse effects. The cardiovascular system undergoes intricate processes forming the heart and blood vessels during fetal development. However, the precise impact of e-cigarette smoke and aerosols on these delicate developmental processes remains elusive. Previous studies have revealed changes in gene expression patterns, disruptions in cellular signaling pathways, and increased oxidative stress resulting from e-cigarette exposure. These findings indicate the potential for e-cigarettes to cause developmental and cardiovascular harm. This comprehensive review article discusses various aspects of electronic cigarette use, emphasizing the relevance of cardiovascular studies in Zebrafish for understanding the risks to human health. It also highlights novel experimental approaches and technologies while addressing their inherent challenges and limitations.

Impact of Electronic Cigarettes, Heated Tobacco Products and Conventional Cigarettes on the Generation of Oxidative Stress and Genetic and Epigenetic Lesions in Human Bronchial Epithelial BEAS-2B Cells

Electronic cigarettes (e-cig) and heated tobacco products (HTP) are often used as smoking cessation aids, while the harm reduction effects of these alternatives to cigarettes are still the subject of controversial debate, in particular regarding their carcinogenic potential. The objective of this study is to compare the effects of e-cig, HTP and conventional cigarette emissions on the generation of oxidative stress and genetic and epigenetic lesions in human bronchial epithelial BEAS-2B cells. Our results show that HTP were less cytotoxic than conventional cigarettes while e-cig were not substantially cytotoxic in BEAS-2B cells. E-cig had no significant effect on the Nrf2 pathway, whereas HTP and cigarettes increased the binding activity of Nrf2 to antioxidant response elements and the expression of its downstream targets HMOX1 and NQO1. Concordantly, only HTP and cigarettes induced oxidative DNA damage and significantly increased DNA strand breaks and chromosomal aberrations. Neither histone modulations nor global DNA methylation changes were found after acute exposure, regardless of the type of emissions. In conclusion, this study reveals that HTP, unlike e-cig, elicit a biological response very similar to that of cigarettes, but only after a more intensive exposure: both tobacco products induce cytotoxicity, Nrf2-dependent oxidative stress and genetic lesions in human epithelial pulmonary cells. Therefore, the health risk of HTP should not be underestimated and animal studies are required in order to determine the tumorigenic potential of these emerging products.

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.

The impact of e-cigarette exposure on different organ systems: A review of recent evidence and future perspectives

The use of electronic cigarettes (e-cigs) is rapidly increasing worldwide and is promoted as a smoking cessation tool. The impact of traditional cigs on human health has been well-defined in both animal and human studies. In contrast, little is known about the adverse effects of e-cigs exposure on human health. This review summarizes the impact of e-cigs exposure on different organ systems based on the rapidly expanding recent evidence from experimental and human studies. A number of growing studies have shown the adverse effects of e-cigs exposure on various organ systems. The summarized data in this review indicate that while e-cigs use causes less adverse effects on different organs compared to traditional cigs, its long-term exposure may lead to serious health effects. Data on short-term organ effects are limited and there is no sufficient evidence on long-term organ effects. Moreover, the adverse effects of secondhand and third hand e-cigs vapour exposure have not been thoroughly investigated in previous studies. Although some studies demonstrated e-cigs used as a smoking cessation tool, there is a lack of strong evidence to support it. While some researchers suggested e-cigs as a safer alternative to tobacco smoking, their long-term exposure health effects remain largely unknown. Therefore, more epidemiological and prospective studies including mechanistic studies are needed to address the potential adverse health effects of e-cigs to draw a firm conclusion about their safe use. A wide variation in e-cigs products and the lack of standardized testing methods are the major barriers to evaluating the existing data. Specific regulatory guidelines for both e-cigs components and the manufacturing process may be effective to protect consumer health.

Flavoured and nicotine-containing e-liquids impair homeostatic properties of an alveolar-capillary cell model

Most people consider that electronic cigarettes are safer than tobacco and are marketed as quit-smoking products. The e-liquid, which usually contains propylene glycol (PG) and vegetable glycerin (VG) in different ratios, nicotine and a wide variety of flavours, is heated by a coil and the aerosol droplets are primarily delivered to the alveolar area where nicotine and other molecules cross the alveolar-capillary barrier (ACB). However, e-cigarettes effects on the ACB are not yet established. In our study, a well-characterised in vitro model of the ACB was exposed to PG and VG and to five flavoured e-liquids with and without nicotine. The vehicles, due to their hypertonic properties, modulated the ACB integrity by modifying occludin expression. Below a 10% concentration, the vehicles did not trigger oxidative stress or cell death. Different results were observed between flavoured e-liquids: while red fruits and mint-eucalyptus disrupted ACB integrity, triggered oxidative stress and cell death, blond tobacco had no worse effect compared to the vehicles. However, the addition of nicotine in the latter e-liquid increased oxidative stress and cell death compared to the vehicles. Finally, mint-eucalyptus e-liquid increased some inflammation markers. Our results revealed that e-liquids alter ACB homeostasis, depending on flavour and nicotine presence.

Toxicological Assessment of Particulate and Metal Hazards Associated with Vaping Frequency and Device Age

Electronic nicotine delivery systems (ENDS) aerosols are complex mixtures of chemicals, metals, and particles that may present inhalation hazards and adverse respiratory health risks. Despite being considered a safer alternative to tobacco cigarettes, metal exposure levels and respiratory effects associated with device aging and vaping frequency have not been fully characterized. In this study, we utilize an automated multi-channel ENDS aerosol generation system (EAGS) to generate aerosols from JUUL pod-type ENDS using tobacco-flavored e-liquid. Aerosol puff fractions (1-50) and (101-150) are monitored and sampled using various collection media. Extracted aerosols are prepared for metal and toxicological analysis using human primary small airway epithelial cells (SAEC). ENDS aerosol-mediated cellular responses, including reactive oxygen species (ROS), oxidative stress, cell viability, and DNA damage, are evaluated after 24 h and 7-day exposures. Our results show higher particle concentrations in later puff fractions (0.135 mg/m3) than in initial puff fractions (0.00212 mg/m3). Later puff fraction aerosols contain higher toxic metal concentrations, including chromium, copper, and lead, which elicit increased levels of ROS followed by significant declines in total glutathione and cell viability. Notably, a 30% increase in DNA damage was observed after 7 days because of later puff fraction exposures. This work is consistent with ENDS aerosols becoming more hazardous across the use of pre-filled pod devices, which may threaten respiratory health.

Cytotoxicity and cell injuries of flavored electronic cigarette aerosol and mainstream cigarette smoke: A comprehensive in vitro evaluation

INTRODUCTION

Although electronic cigarettes (e-cigarettes) have attracted much attention due to their claimed harm-reduction effects compared with conventional cigarettes, the adverse effects of e-cigarette aerosol exposure on human health are still unclear. In this work we compared the cytotoxic effects of combustion cigarettes with four commercially available flavored electronic cigarettes and their main components on ten cell lines. Cell injury mechanism of e-cigarette aerosol and combustible cigarette smoke was also explored using cellular models.

METHODS

Eleven kinds of e-cigarettes aerosol condensates (ECSCs) and cigarette smoke constituent's condensates (CSC) were collected by Cambridge filter pad, and the nicotine contents were determined by UPLC to provide an equivalent nicotine dosage. The CCK-8 assay was used to measure the cell viability differences between ECSC and CSC. Based on RNA-seq results, we compared the effects of ECSC and CSC on various cell injury pathways. Oxidative stress and inflammatory responses were further tested by Western Blot, immunofluorescence, and qRT-PCR assays.

RESULTS

CSC was found to be more cytotoxic than flavored ECSC and their main components, and BEAS-2B cell line was the most sensitive cells by comparing the IC50 value. With prolonged exposure duration and higher doses, ECSC began to exhibit cytotoxicity at and above 72 µg/mL. The IC50 values of ECSC were 15-fold higher than that of CSC. Transcriptome analyses indicated that cell injury-related processes were enriched after the treatment of CSC. CSC could significantly induce more oxidative stress and inflammatory signals than ECSC.

CONCLUSION

ECSCs and their components induced significantly less cytotoxicity than CSC under the laboratory exposure conditions, and CSC caused much severe cell injuries. Our study adds to the body of scientific evidence for a more comprehensive safety evaluation of e-cigarette products as compared to cigarettes.

Smoking, e-cigarettes and the effect on respiratory symptoms among a population sample of youth: Retrospective cohort study

INTRODUCTION

E-cigarettes have been steadily increasing in popularity, both as cessation methods for smoking and for recreational and social reasons. This increase in vaping may pose cardiovascular and respiratory risks. We aimed to assess respiratory symptoms in youth users of e-cigarettes and cigarettes.

METHODS

A retrospective survey design was utilized to assess Canadian youth aged 16-25 years. Participants were recruited from the Ontario Tobacco Research Unit Youth and Young Adult Research Registration Panel November 2020 to March 2021. A total of 3082 subjects completed the baseline survey. Of these, 2660 individuals who did not have asthma were included in the analysis. The exposure of interest was pack-equivalent years, a novel measure of vaping exposure equivalent conceptually to cigarette pack years incorporating number of puffs per day, number of days vaped per month, and number of years vaped. Respiratory symptoms were measured using the five-item Canadian Lung Health Test. Poisson regression analyses were performed while adjusting for demographic confounders, stratified by smoking status. A non-stratified model tested the interaction of status and vaping dose and the effect of vaping device used was assessed among ever vapers. Analyses controlled for demographic characteristics, use of cannabis and alcohol, and survey date.

RESULTS

Each additional puff year increased the rate ratio (RR) of respiratory symptoms by a factor of 11.36 (95% CI: 4.61-28.00; p<0.001) for never smokers, but among current daily smokers higher pack-equivalent years were not associated with more respiratory symptoms (RR=0.83; 95% CI: 0.23-3.11). Among current vapers, those using pod-style devices were more likely to have more respiratory symptoms (RR=1.25; 95% CI: 1.08-1.45) after adjusting for dose.

CONCLUSIONS

Vaping is associated with an increased risk of reporting respiratory symptoms among never smoking youth and non-daily ever cigarette smokers. Use of e-cigarettes among non-smokers should be discouraged.

The point on the electronic cigarette more than 10 years after its introduction

Electronic cigarettes (e-cigarettes) are battery-powered devices containing a liquid based on propylene glycol or vegetable glycerin, compounds which, when vaporized, act as a vehicle for nicotine, flavours, and other chemical components. These devices have been marketed without clear evidence of risks, long-term safety, and efficacy as a means of traditional smoking cessation. Recent clinical studies have shown how the use of the e-cigarette, combined with adequate psychological support, can be effective in reducing traditional smoking but not nicotine addiction. However, meta-analyses of observational studies have not confirmed this efficacy. Several studies have also highlighted an increase in sympathetic tone, vascular stiffness, and endothelial dysfunction, all factors associated with an increased cardiovascular risk. Clinicians, therefore, should carefully monitor the possible risks to public health deriving from the use of e-cigarettes and should discourage non-smokers and adolescents from using such devices. Finally, particular attention should be paid to smokers so that the combined use of electronic and traditional cigarettes can be limited as much as possible.

Associations Between Perceptions of e-Cigarette Harmfulness and Addictiveness and the Age of E-Cigarette Initiation Among the Population Assessment of Tobacco and Health (PATH) Youth

Introduction

Youth perceptions of harmfulness and addictiveness of e-cigarettes may impact the age that they initiate e-cigarette use, but this has not been investigated previously.

Methods

Youth (12-17 years old) never e-cigarette users at their first wave of PATH participation (waves 1-3, 2013-2016) were included. PATH questions on absolute perceptions of e-cigarette harmfulness and addictiveness were used as exposures. Interval-censored Cox proportional hazards models were used to estimate the impact of perceptions of harmfulness, and perceptions of addictiveness on (i) the age of initiation of e-cigarette use and (ii) age of first reporting past 30-day e-cigarette use, while controlling for covariates.

Results

Youth who perceive e-cigarettes as having no/little harm had increased risk of initiating both ever e-cigarette use (AHR = 2.04; 95%CI = 1.74-2.40) and past 30-day e-cigarette use (AHR = 2.64; 95%CI = 2.07-3.37) at earlier ages compared to youth who perceive e-cigarettes as having a lot of harm. Youth who perceive the likelihood of becoming addicted to e-cigarettes to be very/somewhat unlikely had increased risk of an earlier age of both ever (AHR = 1.28; 95%CI = 1.07-1.52) and past 30-day (AHR = 1.36; 95%CI = 1.04-1.79) e-cigarette initiation compared to youth who perceived the likelihood of becoming addicted to e-cigarettes to be somewhat/very likely.

Conclusion

These results highlight the importance of communicating to youth the potential for health harms and addiction from e-cigarette use in prevention and intervention campaigns, as those with the lowest perceptions of harmfulness and addictiveness had the earliest ages of e-cigarette initiation.