Effect of Heating on Physicochemical Property of Aerosols during Vaping

E-Cigarette or Vaping Product Use-Associated Lung Injury: A Comprehensive Review

E-cigarette or vaping product use-associated lung injury (EVALI) is a critical and potentially fatal form of lung injury that gained considerable public health concern in 2019. The use of e-cigarettes and vaping products is causally associated with EVALI, a condition characterized by a constellation of respiratory symptoms, such as coughing, shortness of breath, and chest pain. This comprehensive narrative literature review explores the complexities of EVALI, including its association with the structure and composition of e-cigarettes and its epidemiology, pathogenesis, clinical and radiological manifestations, management strategies, and public health implications. Moreover, it uncovers the long-term repercussions of EVALI and underscores the ongoing research endeavors designed to mitigate and comprehend the risks associated with using e-cigarettes.

Electronic Cigarette-Derived Metals: Exposure and Health Risks in Vapers

Despite the popularity of electronic cigarettes (e-cigs) among adolescent and youth never-smokers and adult smokers seeking a less harmful substitute for tobacco cigarettes, the long-term health impact of vaping is largely unknown. Biochemical, molecular, and toxicological analyses of biospecimens from e-cig users as well as assays in relevant in vitro models and in silico studies can identify chemical constituents of e-cig emissions that may contribute to the disease-causing potential of vaping. E-cig aerosol contains a wide range of toxic and carcinogenic compounds, of which metals are of particular concern. This is due to the known or suspected role of various metals in the pathogenesis of numerous diseases. Many metals and metalloids (herein referred to as "metals") have been detected in e-cig liquid (e-liquid) and aerosol and/or in cells, tissues, biofluids, or other specimens from e-cig users. Metals can contaminate the ingredients of e-liquid or corrode from the internal components of the e-cig device. Metals may also be directly aerosolized from the surface of the heating element or other parts of the device. Inhalation of e-cig metal emissions in habitual vapers and nonusers through secondary exposure may increase the body burden of toxic and carcinogenic chemicals. This review summarizes the state of research on e-cig-derived metals and their contributions to the estimated health risks of vaping. Highlighting the chemical composition of e-cig liquid and aerosol, it focuses on the metal contents of the inhaled aerosol and the health risks associated with this exposure. Emphasis is placed on adolescents and youth who are vulnerable populations and bear a disproportionate burden of risk and harm from tobacco products. The gaps in knowledge, methodological challenges, and opportunities ahead are discussed. The importance of translating research findings into actionable information that can be used for the regulation of the manufacturing of tobacco products is underscored.

The effects of electronic smoking on dental caries and proinflammatory markers: a systematic review and meta-analysis

Introduction

Smoking and the use of electronic cigarettes (e-cigs) are common practices that have significant consequences for oral health. Although the negative impact of traditional tobacco products on oral tissues is widely known, the emergence of e-cigs poses a new obstacle. This review summarises existing data on the influence of e-cigs on oral health, with a specific emphasis on dental caries and pro-inflammatory agents.

Methods

A comprehensive search was conducted via PubMed, Web of Science, Embase, and Scopus to identify relevant studies published until September 2024. The structured search strategy uncovered 42 articles that were read in full text. The included articles consisted of clinical trials, observational studies, and laboratory investigations that examined the impact of e-cig aerosol on oral bacteria and pro-inflammatory markers and its potential to contribute to dental caries.

Results

The findings indicate that e-cig users may have a higher prevalence of dental caries compared with non-smokers. Most studies focusing on bacteria showed that vaping may inhibit normal flora, giving cariogenic bacteria a chance to grow more. This finding indicates a notable oral health risk associated with vaping. Meta-analyses suggest no effect of using e-cigs on the levels of TNF-α, IL-1β, IL-6, and IL-8 in saliva, even if it may affect their levels in GCF. However, in GCF, only one study reported TNF-α and IL-1β, and only two studies reported IL-6 and IL-8. Nevertheless, the effects of e-cigs on dental caries require further investigation since the data do not provide a clear picture.

Discussion

This review emphasises the necessity for ongoing research to clarify the mechanisms that cause these consequences and to guide public health policies aimed at reducing the harm caused by e-cigarettes.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/view/CRD42024537910, PROSPERO (CRD42024537910).

Sample preparation methods for elemental analysis in electronic cigarette aerosols: a critical review

In the last decade, e-cigarettes have been marketed as a less harmful alternative to classical tobacco smoking and are currently being used by millions of people. An e-cigarette consists of an e-liquid and a heating device, generating an aerosol that the user can inhale. Recently, several studies have shown that metals and metalloids, including As, Cd, and Pb, known carcinogens, were present in these aerosols. To ensure the accuracy of dose-toxicity estimations, it is essential to have access to reliable and reproducible methods for estimating the dose in question. Although more standardization methodologies were introduced in the analysis of metal(loid)s from aerosols, a huge divergence in sample preparation can be found in the literature. This work aimed to provide an overview of the sample preparation methods used to quantify these metal(loid)s. Therefore, a literature search was conducted in September 2024, that followed the PRISMA guidelines. Among the 48 articles selected, a wide variability in sample preparation was observed, specifically variations in aerosol generation characteristics and collection techniques. Despite the widespread use of methods as filters and impingers, many studies failed to validate critical steps such as aerosol recovery, blank corrections, and the extent of matrix effects. In addition, poor inorganic methodological practices were often applied, such as excessive use of glass materials for aerosol collection or other sample preparation steps. Therefore, further standardization of methodologies is urgently needed to improve the reliability of metal quantification in e-cigarette aerosols, which could potentially enhance regulatory frameworks and facilitate the routine analysis of e-cigarette emissions.

Effect of electronic cigarette atomising power and flavour on aerosol size-segregated metal concentration and inhalation risk

INTRODUCTION

Although numerous studies have estimated the inhalation dose of metals emitted from electronic cigarettes (e-cigs), the impact of factors including aerosol size and the atomising power of e-cig aerosols on estimating the inhalation dose of metals remains underexplored. A comprehensive understanding of these determinants is essential to assess the health risks associated with inhaling e-cig aerosols, which may contain potentially harmful metals.

OBJECTIVES

The aim of this study is to elucidate the mass and inhalation doses of potentially harmful metals in e-cig aerosols by different particle size and their association with the various atomising powers of e-cig devices and flavours.

METHODS

Size-segregated e-cig aerosols were generated and collected in a exposure chamber, using an 11-stage cascade impactor for the analyses of aerosol mass and metals. The metal deposition dose in the human respiratory tract was calculated using a mathematical respiratory deposition estimation model and metal mass concentration by the size of aerosols.

RESULTS

In this study, the results showed that neither an increase in atomising power (from 5 to 20 W) nor e-cig flavours resulted in a significant increase in a metal deposition in the respiratory tracts. Although the factors did not significantly affect the calculated respiratory deposition of harmful metals under typical e-cig usage assumption, the estimated hazard index exceeded 1.0.

CONCLUSION

The calculated health risks suggest substantial risks of inhalation of metal aerosols from e-cig use.

Increasing coil temperature of a third-generation e-cigarette device modulates C57BL/6 mouse lung immune cell composition and cytokine milieu independently of aerosol dose

Higher coil temperature in e-cigarette devices increases the formation of aerosols and toxicants, such as carbonyls. At present, the health implications of vaping at higher temperatures, including exacerbation of pulmonary inflammation, are largely unknown when aerosol dose is considered. To isolate the pulmonary effects of coil temperature, C57BL/6 mice were exposed to e-cigarette aerosols generated at lower (190°C) or higher (250°C) temperature for 3 days, while maintaining a similar chamber aerosol concentration. Increasing coil temperature did not markedly alter aerosol mass-normalized emissions of select carbonyls formed from thermal degradation pathways including formaldehyde, acetaldehyde, propionaldehyde, and acetone under the tested environment. Total bronchoalveolar cells, primarily macrophages, were significantly decreased in mice exposed to aerosols generated with higher coil temperatures compared to lower temperature exposures. The gene expression of IFNβ, IL-1β, TNFα, and IL-10 in mouse lung tissue was significantly reduced following e-cigarette exposure under both conditions, compared to filtered air exposure. Higher temperature exposures further exacerbated downregulation of IFNβ and IL-1β. Data suggest that higher temperature vaping might modulate acute pulmonary immune responses, potentially inducing immune suppression, even when normalized for aerosol dose exposure. Coil temperature thus appears to be an important parameter that needs to be regulated to ensure harm reduction for e-cigarette users.

Physical and Chemical Characterization of Aerosols Produced from Experimentally Designed Nicotine Salt-Based E-Liquids

Nicotine salt-based e-liquids deliver nicotine more rapidly and efficiently to electronic nicotine delivery system (ENDS) users than freebase nicotine formulations. Nicotine salt-based products represent a substantial majority of the United States ENDS market. Despite the popularity of nicotine salt formulations, the chemical and physical characteristics of aerosols produced by nicotine salt e-liquids are still not well understood. To address this, this study reports the harmful and potentially harmful constituents (HPHCs) and particle sizes of aerosols produced by laboratory-made freebase nicotine and nicotine salt e-liquids. The nicotine salt e-liquids were formulated with benzoic acid, citric acid, lactic acid, malic acid, or oxalic acid. The nicotine salt aerosols had different HPHC profiles than the freebase nicotine aerosols, indicating that the carboxylic acids were not innocent bystanders. The polycarboxylic acid e-liquids containing citric acid, malic acid, or oxalic acid produced higher acrolein yields than the monocarboxylic acid e-liquids containing benzoic acid or lactic acid. Across most PG:VG ratios, nicotine benzoate or nicotine lactate aerosols contained the highest nicotine quantities (in %) and the highest nicotine yields (per milligram of aerosol). Additionally, the nicotine benzoate and nicotine lactate e-liquids produced the highest carboxylic acid yields under all tested conditions. The lower acid yields of the citric, malic, and oxalic acid formulations are potentially due to a combination of factors such as lower transfer efficiencies, lower thermostabilities, and greater susceptibility to side reactions because of their additional carboxyl groups serving as new sites for reactivity. For all nicotine formulations, the particle size characteristics were primarily controlled by the e-liquid solvent ratios, and there were no clear trends between nicotine salt and freebase nicotine aerosols that indicated nicotine protonation affected particle size. The carboxylic acids impacted aerosol output, nicotine delivery, and HPHC yields in distinct ways such that interchanging them in ENDS can potentially cause downstream effects.

Online quantification of nicotine in e-cigarette aerosols by vacuum ultraviolet photoionization mass spectrometry

The growing popularity of e-cigarettes and the associated risks of nicotine addiction present a new challenge to global public health security. Measuring the nicotine levels in e-cigarette aerosols is essential to assess the safety of e-cigarettes. In this study, a rapid in situ method was developed for online quantification of nicotine in e-cigarette aerosols by using a homemade vacuum ultraviolet photoionization aerosol mass spectrometer (VUV-AMS). E-cigarette liquids with different nicotine concentrations were prepared to generate aerosols containing different levels of nicotine, which were employed as the calibration sources for nicotine quantification by VUV-AMS. The results showed that the mass concentration of nicotine in e-cigarette aerosols has a good linear relationship with its signal intensity in the mass spectrum, and the limits of detection and quantitation of nicotine by VUV-AMS were found to be 2.0 and 6.2 μg per puff respectively. Then the online method was utilized to measure five commercial e-cigarettes, and their nicotine yields were determined to be between 31 and 188 μg per puff with the nicotine fluxes from 7.7 to 70 μg s-1, agreeing with the results of the gas chromatography with a flame ionization detector (GC-FID). This study demonstrated the feasibility and advantages of VUV-AMS for quick quantification of nicotine in e-cigarette aerosols within seconds.

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.

Review of quantitative and functional lung imaging evidence of vaping-related lung injury

Introduction

The pulmonary effects of e-cigarette use (or vaping) became a healthcare concern in 2019, following the rapid increase of e-cigarette-related or vaping-associated lung injury (EVALI) in young people, which resulted in the critical care admission of thousands of teenagers and young adults. Pulmonary functional imaging is well-positioned to provide information about the acute and chronic effects of vaping. We generated a systematic review to retrieve relevant imaging studies that describe the acute and chronic imaging findings that underly vaping-related lung structure-function abnormalities.

Methods

A systematic review was undertaken on June 13th, 2023 using PubMed to search for published manuscripts using the following criteria: [("Vaping" OR "e-cigarette" OR "EVALI") AND ("MRI" OR "CT" OR "Imaging")]. We included only studies involving human participants, vaping/e-cigarette use, and MRI, CT and/or PET.

Results

The search identified 445 manuscripts, of which 110 (668 unique participants) specifically mentioned MRI, PET or CT imaging in cases or retrospective case series of patients who vaped. This included 105 manuscripts specific to CT (626 participants), three manuscripts which mainly used MRI (23 participants), and two manuscripts which described PET findings (20 participants). Most studies were conducted in North America (n = 90), with the remaining studies conducted in Europe (n = 15), Asia (n = 4) and South America (n = 1). The vast majority of publications described case studies (n = 93) and a few described larger retrospective or prospective studies (n = 17). In e-cigarette users and patients with EVALI, key CT findings included ground-glass opacities, consolidations and subpleural sparing, MRI revealed abnormal ventilation, perfusion and ventilation/perfusion matching, while PET showed evidence of pulmonary inflammation.

Discussion and conclusion

Pulmonary structural and functional imaging abnormalities were common in patients with EVALI and in e-cigarette users with or without respiratory symptoms, which suggests that functional MRI may be helpful in the investigation of the pulmonary health effects associated with e-cigarette use.

Evaluation of the Effect of Electronic Cigarette Devices/Vape on the Color of Dental Ceramics: An In Vitro Investigation

The use of vaping or electronic cigarette devices (ECDs) has recently increased as an alternative to conventional tobacco smoking products. By recording the CIELAB coordinates (L*a*b*) and computing the total color difference (ΔE) values using a spectrophotometer, the effect of ECDs on contemporary aesthetic dental ceramics was investigated in this in-vitro study. A total of seventy-five (N = 75) specimens from five different (n = 15) dental ceramic materials (Pressable ceramics (PEmax); Pressed and layered ceramics (LEmax); Layered zirconia (LZr); Monolithic zirconia (MZr) and Porcelain fused to metal (PFM)) were prepared and exposed to aerosols produced by the ECDs. The color assessment was performed using a spectrophotometer at six time intervals (0 = baseline; 250-puff exposures; 500-puff exposures; 750-puff exposures; 1000-puff exposures; 1250-puff exposures; and 1500-puff exposures). By recording L*a*b* and computing total color difference (ΔE) values, the data were processed. A one-way ANOVA and Tukey procedure for pairwise comparisons were used to assess color differences between tested ceramics (p < 0.05). All test materials demonstrated significant color differences (ΔE) after exposure to vaping (p < 0.05). The LZr group displayed noticeably high ΔE values at all the distinct puff exposure intervals, with the highest ΔE value of (13.67) after 1500 puffs. The lowest (ΔE) values were observed in the PFM group after 250 and 500 puffs (0.85 and 0.97, respectively). With the exception of the group PEmax (p = 0.999), all groups produced readings of "ΔE" that indicated significant differences (p < 0.05) at various degrees of puff exposures. ECDs can noticeably alter the color of the dental ceramics affecting the esthetics of the patients. All the materials tested demonstrated significant color changes (ΔE > 3.33) above the clinically acceptable threshold, except for the PFM and PEmax group (ΔE < 3.33) which showed color stability after exposure to the ECDs.

The risk profile of electronic nicotine delivery systems, compared to traditional cigarettes, on oral disease: a review

The use of electronic nicotine delivery systems (ENDS) has exploded, especially among teenagers and new smokers, amid widespread awareness of the dangers of traditional tobacco and restrictions on smoking. However, the risk effects of ENDS on physical health, especially oral health, are still ambiguous. The purpose of this study was to review the available evidence on risks of ENDS on oral health, and compares the differences between ENDS and traditional cigarettes. For heavy smokers, transferring the addiction of tobacco to ENDS can be less harmful to periodontal condition and physical health but is not completely without risk. The components of ENDS vapor have cytotoxic, genotoxic, and carcinogenic properties, and its usage may be associated with a wide range of oral health sequelae. The chemicals in ENDS increase the susceptibility to tooth decay, increase the risk of periodontal disease, peri-implant, and oral mucosal lesions. Nicotine aerosols from ENDS can be a potential risk factor for oral cancer due to the presence of carcinogenic components. Compared to smoking traditional cigarettes, the harm associated with ENDS use may be underestimated due to the reduced ability to control vaping behavior, ease of ENDS access, fewer vaping area restrictions, and better taste. Currently, the available evidence suggests that ENDS may be a safer alternative to traditional tobacco products. Though most oral symptoms experienced by ENDS users are relatively mild and temporary compared to traditional cigarettes, the dangers of ENDS still exist. However, further research with longer follow-up periods is required to establish the long-term safety of ENDS.

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.

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.

E-Cigarette (E-Cig) Liquid Composition and Operational Voltage Define the In Vitro Toxicity of Δ8Tetrahydrocannabinol/Vitamin E Acetate (Δ8THC/VEA) E-Cig Aerosols

The 2019 United States outbreak of E-cigarette (e-cig), or Vaping, Associated Acute Lung Injury (EVALI) has been linked to presence of vitamin E acetate (VEA) in Δ8tetrahydrocannabinol (Δ8THC)-containing e-liquids, as supported by VEA detection in patient biological samples. However, the pathogenesis of EVALI and the complex physicochemical properties of e-cig emissions remain unclear, raising concerns on health risks of vaping. This study investigates the effect of Δ8THC/VEA e-liquids and e-cig operational voltage on in vitro toxicity of e-cig aerosols. A novel E-cigExposure Generation System platform was used to generate and characterize e-cig aerosols from a panel of Δ8THC/VEA or nicotine-based e-liquids at 3.7 or 5 V. Human lung Calu-3 cells and THP-1 monocytes were exposed to cell culture media conditioned with collected e-cig aerosol condensate at doses of 85 and 257 puffs/m2 lung surface for 24 h, whereafter specific toxicological endpoints were assessed (including cytotoxicity, metabolic activity, reactive oxygen species generation, apoptosis, and inflammatory cytokines). Higher concentrations of gaseous volatile organic compounds were emitted from Δ8THC/VEA compared with nicotine-based e-liquids, especially at 5 V. Emitted PM2.5 concentrations in aerosol were higher for Δ8THC/VEA at 5 V and averagely for nicotine-based e-liquids at 3.7 V. Overall, aerosols from nicotine-based e-liquids showed higher bioactivity than Δ8THC/VEA aerosols in THP-1 cells, with no apparent differences in Calu-3 cells. Importantly, presence of VEA in Δ8THC and menthol flavoring in nicotine-based e-liquids increased cytotoxicity of aerosols across both cell lines, especially at 5 V. This study systematically investigates the physicochemical and toxicological properties of a model of Δ8THC/VEA and nicotine e-cigarette condensate exposure demonstrating that pyrolysis of these mixtures can generate hazardous toxicants whose synergistic actions potentially drive acute lung injury upon inhalation.