Lung Toxicity of Condensed Aerosol from E-CIG Liquids: Influence of the Flavor and the In Vitro Model Used

The diffusion of e-cigarette (e-CIG) opens a great scientific and regulatory debate about its safety. The huge number of commercialized devices, e-liquids with almost infinite chemical formulations and the growing market demand for a rapid and efficient toxicity screen system that is able to test all of these references and related aerosols. A consensus on the best protocols for the e-CIG safety assessment is still far to be achieved, since the huge number of variables characterizing these products (e.g., flavoring type and concentration, nicotine concentration, type of the device, including the battery and the atomizer). This suggests that more experimental evidences are needed to support the regulatory frameworks. The present study aims to contribute in this field by testing the effects of condensed aerosols (CAs) from three main e-liquid categories (tobacco, mint, and cinnamon as food-related flavor), with (18 mg/mL) or without nicotine. Two in vitro models, represented by a monoculture of human epithelial alveolar cells and a three-dimensional (3D) co-culture of alveolar and lung microvascular endothelial cells were used. Cell viability, pro-inflammatory cytokines release and alveolar-blood barrier (ABB) integrity were investigated as inhalation toxicity endpoints. Results showed that nicotine itself had almost no influence on the modulation of the toxicity response, while flavor composition did have. The cell viability was significantly decreased in monoculture and ABB after exposure to the mints and cinnamon CAs. The barrier integrity was significantly affected in the ABB after exposure to cytotoxic CAs. With the exception of the significant IL-8 release in the monoculture after Cinnamon exposure, no increase of inflammatory cytokines (IL-8 and MCP-1) release was observed. These findings point out that multiple assays with different in vitro models are able to discriminate the acute inhalation toxicity of CAs from liquids with different flavors, providing the companies and regulatory bodies with useful tools for the preliminary screening of marketable products.

Characteristics and outcomes of e-cigarette exposure incidents reported to 10 European Poison Centers: a retrospective data analysis

Background

The use of e-cigarettes has increased during the past few years. Exposure to e-cigarette liquids, whether intentional or accidental, may lead to adverse events our aim was to assess factors associated with e-cigarette exposures across European Union Member States (EU MS).

Methods

A retrospective analysis of exposures associated with e-cigarettes reported to national poison centers was performed covering incidents from 2012 to March 2015 from 10 EU MS. De-identified and anonymous raw data was acquired.

Results

In total, 277 incidents were reported. Unintentional exposure was the most frequently cited type of exposure (71.3%), while e-cigarette refill vials were responsible for the majority of the reported incidents (87.3%). Two-thirds of all exposures (67.5%) occurred as ingestion of e-liquids, which was more frequent among children (≤ 5 years, 6–18 years) compared to adults (87.0% vs. 59.3% vs. 57.6%, p < 0.001 respectively), exposure via the respiratory (5.4% vs. 22.2% vs. 22.2%, p < 0.001) were more frequent among paediatric patients while ocular routes (2.2% vs. 3.7% vs. 11.4%, p = 0.021) were more frequent among adults. Logistic regression analyses indicated that paediatric incidents (≤ 5 years) were more likely to be through ingestion (adjusted Odds Ratio [aOR] = 4.36, 95% Confidence Interval [C.I.]: 1.87–10.18), but less likely to have a reported clinical effect (aOR = 0.41, 95% C.I.: 0.21–0.82).

Conclusions

Our study highlighted parameters related to e-cigarette exposure incidents in 10 EU MS, the results of which indicate that consideration should be given to the design features which may mitigate risks, thereby protecting users, non-users and especially children.

Flavored e-cigarette liquids and cinnamaldehyde impair respiratory innate immune cell function

Innate immune cells of the respiratory tract are the first line of defense against pathogenic and environmental insults. Failure of these cells to perform their immune functions leaves the host susceptible to infection and may contribute to impaired resolution of inflammation. While combustible tobacco cigarettes have been shown to suppress respiratory immune cell function, the effects of flavored electronic cigarette liquids (e-liquids) and individual flavoring agents on respiratory immune cell responses are unknown. We investigated the effects of seven flavored nicotine-free e-liquids on primary human alveolar macrophages, neutrophils, and natural killer (NK) cells. Cells were challenged with a range of e-liquid dilutions and assayed for their functional responses to pathogenic stimuli. End points included phagocytic capacity (neutrophils and macrophages), neutrophil extracellular trap formation, proinflammatory cytokine production, and cell-mediated cytotoxic response (NK cells). E-liquids were then analyzed via mass spectrometry to identify individual flavoring components. Three cinnamaldehyde-containing e-liquids exhibited dose-dependent broadly immunosuppressive effects. Quantitative mass spectrometry was used to determine concentrations of cinnamaldehyde in each of the three e-liquids, and cells were subsequently challenged with a range of cinnamaldehyde concentrations. Cinnamaldehyde alone recapitulated the impaired function observed with e-liquid exposures, and cinnamaldehyde-induced suppression of macrophage phagocytosis was reversed by addition of the small-molecule reducing agent 1,4-dithiothreitol. We conclude that cinnamaldehyde has the potential to impair respiratory immune cell function, illustrating an immediate need for further toxicological evaluation of chemical flavoring agents to inform regulation governing their use in e-liquid formulations.

Universal electronic-cigarette test: physiochemical characterization of reference e-liquid

BACKGROUND

Despite the rising health and safety concerns of e-cigarettes, a universal e-cigarette testing method is still in its early developmental stage. The aim of this study was to develop an e-liquid Reference Material that can be used to improve accuracy and reproducibility of research results, and advance health risk assessment of e-cigarette products.

METHODS

E-liquid Reference Material was developed by purity assessment, gravimetric measurement, homogeneity testing, and stability testing with material and instrument traceability (adopted from ISO 35:2006E).

RESULTS

Homogeneity tests showed e-liquid Reference Material requires ≥ 1 h rotation at a speed of 5 rpm to reach complete homogeneity. Stability tests showed homogeneity is intact for at least 2 weeks without secondary separation, and e-liquids are stable in 21 °C-50 °C thermocycling conditions up to 72 h. A change in the e-liquid color was first observed at day seven, and progressed to 2- and 16 - fold increase in absorbance by one and 6 months respectively. We found that e-liquids do not have inherent material instabilities such as immiscibility or secondary separation. However, discrepancies in concentration and composition arose mainly due to viscosity of propylene glycol and glycerin. Aerosol generated from the e-liquid Reference Material had 16 chemical-byproducts and was composed of ~634,000 particles of which 38% were Fine Particulate Matters (<0.5 μm in diameter).

CONCLUSIONS

The efforts described here to create a standardized e-liquid Reference Material aim to provide unbiased and robust testing parameters that may be useful for researchers, the industry and government agencies. Additionally, the reference e-liquid could open a channel of conversation among different laboratories by providing the means of independent verification and validation while establishing a system of transparency and reproducibility in materials and methods.

Drug Vaping: From the Dangers of Misuse to New Therapeutic Devices

Users of e-cigarettes are unwitting volunteers participating in a worldwide epidemiological study. Because of the obvious benefits of e-cigarettes compared with traditional cigarette smoking, these electronic devices have been introduced all around the world to support tobacco smoking cessation. Same potential harm reduction could be considered by cannabis vaping for marijuana smokers. However, the toxicities of liquids and aerosols remain under investigation because although the use of e-cigarettes is likely to be less harmful than traditional cigarette smoking, trace levels of contaminants have been identified. Simultaneously, other electronic devices, such as e-vaporisers, e-hookahs or e-pipes, have been developed and commercialised. Consequently, misuse of electronic devices has increased, and experimentation has been documented on Internet web fora. Although legal and illegal drugs are currently consumed with these e-devices, no scientific papers are available to support the observations reported by numerous media and web fora. Moreover, building on illegal drug vaping and vaporisation with e-devices (vaping misuse), legal drug vaping (an alternative use of vaping) could present therapeutic benefits, as occurs with medical cannabis vaporisation with table vaporisers. This review seeks to synthesise the problems of e-cigarette and liquid refill toxicity in order to introduce the dangers of illegal and legal drugs consumed using vaping and vaporisation for recreational purposes, and finally, to present the potential therapeutic benefits of vaping as a new administration route for legal drugs.

Determination of nicotine, glycerol, propylene glycol and water in electronic cigarette fluids using quantitative 1 H NMR

The variability of the electronic cigarette liquids (e-liquid) composition has the potential to influence not only the amount of nicotine delivered to the user, but also the type and amount of generated byproducts and subsequent health risks. For this reason, it is important to characterize all of the chemical components of e-liquids. We report the development and application of a single ¹H NMR analysis method to identify and quantify the most abundant chemical components (nicotine, glycerol, 1,2-propylene glycol, and water) likely to be present as their influence on the composition of inhaled vapor is not know. For ¹H NMR, the solvent has to dissolve the e-liquids at a concentration sufficient to readily determine the concentration of nicotine present, and the solvent and internal standard cannot possess exchangeable protons which would interfere with determining the concentrations of the analytes of interest. To fulfill these requirements, perdeuterated N,N-dimethylformamide (DMF-d₇) was selected as the solvent, with 1,2,4,5-tetrachloro-3-nitrobenzene as the internal standard. Nicotine concentrations from 58 different e-liquids obtained using ¹H NMR were found to agree with the results from GC-MS analysis. Generally, the amount of nicotine present was close to that claimed by the manufacturer. In some cases, the proportions of 1,2-propylene glycol, glycerol, and water varied significantly between flavors within a brand and within flavors depending on the nicotine content. In one case, 1,2-propylene glycol was identified where the manufacturer had stated none should be present.

Analysis of symptoms and their potential associations with e-liquids' components: a social media study

Background

The electronic cigarette (e-cigarette) market has grown rapidly in recent years. However, causes of e-cigarette related symptoms among users and their impact on health remain uncertain. This research aims to mine the potential relationships between symptoms and e-liquid components, such as propylene glycol (PG), vegetable glycerine (VG), flavor extracts, and nicotine, using user-generated data collected from Reddit.

Methods

A total of 3605 e-liquid related posts from January 1st, 2011 to June 30th, 2015 were collected from Reddit. Then the patterns of VG/PG distribution among different flavors were analyzed. Next, the relationship between throat hit, which was a typical symptom of e-cigarette use, and e-liquid components was studied. Finally, other symptoms were examined based on e-liquid components and user sentiment.

Results

We discovered 3 main sets of findings: 1) We identified three groups of flavors in terms of VG/PG ratios. Fruits, cream, and nuts flavors were similar. Sweet, menthol, and seasonings flavors were classified into one group. Tobacco and beverages flavors were the third group. 2) Throat hit was analyzed and we found that menthol and tobacco flavors, as well as high ratios of PG and nicotine level, could produce more throat hit. 3) A total of 9 systems of 25 symptoms were identified and analyzed. Components including VG/PG ratio, flavor, and nicotine could be possible reasons for these symptoms.

Conclusions

E-liquid components shown to be associated with e-cigarette use symptomology were VG/PG ratios, flavors, and nicotine levels. Future analysis could be conducted based on the structure of e-liquid components categories built in this study. Information revealed in this study could be utilized by e-cigarette users to understand the relationship between e-liquid type and symptoms experienced, by vendors to choose appropriate recipes of e-liquid, and by policy makers to develop new regulations.

An Examination of Electronic Cigarette Content on Social Media: Analysis of E-Cigarette Flavor Content on Reddit

In recent years, the emerging electronic cigarette (e-cigarette) marketplace has shown great development prospects all over the world. Reddit, one of the most popular forums in the world, has a very large user group and thus great influence. This study aims to gain a systematic understanding of e-cigarette flavors based on data collected from Reddit. Flavor popularity, mixing, characteristics, trends, and brands are analyzed. Fruit flavors were mentioned the most (n = 15,720) among all the posts and were among the most popular flavors (n = 2902) used in mixed blends. Strawberry and vanilla flavors were the most popular for e-juice mixing. The number of posts discussing e-cigarette flavors has increased sharply since 2014. Mt. Baker Vapor and Hangen were the most popular brands discussed among users. Information posted on Reddit about e-cigarette flavors reflected consumers' interest in a variety of flavors. Our findings suggest that Reddit could be used for data mining and analysis of e-cigarette-related content. Understanding how e-cigarette consumers' view and utilize flavors within their vaping experience and how producers and marketers use social media to promote flavors and sell products could provide valuable information for regulatory decision-makers.

Laboratory Activity for the Determination of Nicotine in Electronic Cigarette Liquids using Gas Chromatography-Mass Spectrometry

In recent years the prevalence and popularity of electronic cigarettes (ECs) has increased noticeably and a large market for their refillable nicotine solutions (e-liquids) has also rapidly increased. These e-liquids contain nicotine, an addictive and potentially dangerous stimulant, but often the actual nicotine content differs significantly from manufacturers' labelling, due in part to lack of regulation for these products. A laboratory activity for undergraduate students was developed to directly test e-liquids for nicotine content using gas chromatography combined with mass spectrometry (GC-MS) as a means for teaching the instrumentation to undergraduate students using an authentic, real-world example. The activity introduces and/or re-emphasizes the theory and operation of GC-MS, standard/sample preparation, calibration curves, internal standards, selected ion monitoring mode of MS operation, and method validation. The laboratory experiment is designed for students enrolled in Quantitative Analysis courses (like Analytical Chemistry or Instrumental Analysis), but portions are also suitable for lower level chemistry courses or even those designed for allied health professionals or non-chemistry majors. Given the current popularity of ECs, this activity can provide the chemistry curriculum with a timely, real-world, and contemporary application in which crucial course content is taught. Students can also benefit from the inherent discussion of ECs, regulations, and related social aspects of smoking and EC vaping - which can serve as a secondary learning outcome.

Comparative in vitro toxicity profile of electronic and tobacco cigarettes, smokeless tobacco and nicotine replacement therapy products: e-liquids, extracts and collected aerosols

The use of electronic cigarettes (e-cigs) continues to increase worldwide in parallel with accumulating information on their potential toxicity and safety. In this study, an in vitro battery of established assays was used to examine the cytotoxicity, mutagenicity, genotoxicity and inflammatory responses of certain commercial e-cigs and compared to tobacco burning cigarettes, smokeless tobacco (SLT) products and a nicotine replacement therapy (NRT) product. The toxicity evaluation was performed on e-liquids and pad-collected aerosols of e-cigs, pad-collected smoke condensates of tobacco cigarettes and extracts of SLT and NRT products. In all assays, exposures with e-cig liquids and collected aerosols, at the doses tested, showed no significant activity when compared to tobacco burning cigarettes. Results for the e-cigs, with and without nicotine in two evaluated flavor variants, were very similar in all assays, indicating that the presence of nicotine and flavors, at the levels tested, did not induce any cytotoxic, genotoxic or inflammatory effects. The present findings indicate that neither the e-cig liquids and collected aerosols, nor the extracts of the SLT and NRT products produce any meaningful toxic effects in four widely-applied in vitro test systems, in which the conventional cigarette smoke preparations, at comparable exposures, are markedly cytotoxic and genotoxic.

Safety evaluation and risk assessment of electronic cigarettes as tobacco cigarette substitutes: a systematic review

Electronic cigarettes are a recent development in tobacco harm reduction. They are marketed as less harmful alternatives to smoking. Awareness and use of these devices has grown exponentially in recent years, with millions of people currently using them. This systematic review appraises existing laboratory and clinical research on the potential risks from electronic cigarette use, compared with the well-established devastating effects of smoking tobacco cigarettes. Currently available evidence indicates that electronic cigarettes are by far a less harmful alternative to smoking and significant health benefits are expected in smokers who switch from tobacco to electronic cigarettes. Research will help make electronic cigarettes more effective as smoking substitutes and will better define and further reduce residual risks from use to as low as possible, by establishing appropriate quality control and standards.