Carbonyl compounds in electronic cigarette vapors: effects of nicotine solvent and battery output voltage

Advancing low-cost air quality monitor calibration with machine learning methods

Low-cost monitors for measuring airborne contaminants have gained popularity due to their affordability, portability, and ease of use. However, they often exhibit significant biases compared to high-cost reference instruments. For optimal accuracy, these monitors require calibration and validation in their specific environment using expensive reference instruments, which are often scarce and costly. This study proposes machine-learning calibration methods that utilize a single high-cost instrument as an active reference to improve the accuracy of large networks of low-cost monitors. Three machine learning models-linear regression, random forest, and Gradient Boosting Regression (GBR)-were employed. The proposed approach was tested in a controlled chamber under two conditions: environmental simulations with salt- and dust-based aerosols and occupational settings using three electronic cigarette (ECIG) brands. The study involved thirty low-cost GeoAir2 monitors, divided into ten groups of three. Initially, all groups were collocated with a high-cost monitor using Aerosol A to develop prediction and regression models. These models, along with intrinsic error measurements from one group, were then applied to improve data accuracy for the remaining groups using Aerosol B. The results demonstrated substantial improvements in accuracy, with r2 values ranging from 0.91 to 1.00 and RMSE reductions of up to 88 %, depending on the model and aerosol type. GBR consistently provided the highest accuracy and performance, particularly for complex, nonlinear patterns, while linear regression offered a faster, computationally efficient alternative suitable for less demanding scenarios. Random forest models performed moderately well, balancing accuracy and complexity. These methods provide a scalable and cost-effective solution for deploying networked low-cost sensors. Further research is needed to validate these findings in outdoor environments with meteorological and spatial influences, and indoor occupational settings where humidity effects may play a role.

Short-Term and Long-Term Effects of Electronic Cigarettes on Mouse Lungs Following Nose-Only Exposures

Health effects of electronic cigarettes (ECs) remain unknown, despite their popularity. We have determined that ECs produce highly reactive free radicals that could potentially cause damage in exposed tissues, mainly lungs. Goal for this study was to investigate the short- and long-term effects of ECs in mouse lungs. We focused on evaluating lung functions, oxidative stress related markers, and lung injury following nose-only exposures in male and female mice after 4- and 12-week periods. The EC exposure was modeled in vivo using nose-only exposures to C57BL/6 mice. For all studies, E-liquid (60:40; PG:VG) aerosols were compared to sham (compressed air) and to very low non-nicotine cigarette smoke (CS) controls in both sexes. Oxidative stress biomarkers (GSH, 8-Isoprostane, REDD1, and pGSK3β) and their selected downstream (RPS6) as well as upstream (AKT) target proteins in addition to pH2AX were measured by Western blot analysis. Lung function in mice was assessed by flexiVent and the injury scores were calculated following lung histology. Changes in cytology were also observed in cytospins from bronchoalveolar lavage (BALF). The lung injury (LI) score following 12-week exposures was significantly higher with EC and CS in female mice. Higher cell counts in BALF were mainly observed in CS exposed males and females at 4 and 12 weeks. 8-Isoprostane levels were significantly higher in EC and CS exposed males at 12 weeks. pGSK3β/GSK3β was low in males and higher in female mice at 4 weeks, and this difference was more pronounced at 12 weeks in CS exposed mice. Some mice exposed to EC and CS also showed DNA damage, as measured by pH2AX/H2AX expression. Based on the LI score, ECs were placed in between compressed air and CS. Our results showed the differentially expressed inflammation and oxidative stress/damage-related pathways from in vivo exposures to EC aerosols vs CS that could be an effective strategy for identifying EC relevant biomarkers of exposure and potential harm.

A review of analytical techniques for the determination of e-liquid and electronic cigarette aerosol composition

Since the introduction of electronic cigarettes (ECs) to the global market, the composition of e-liquids has been a controversial topic. While some consider ECs to be an effective tool for quitting smoking, their primary criticism lies in the uncertain and varied composition of e-liquids. Manufacturers create the desired formulations by mixing different ratios of humectants, flavorings, nicotine, cannabinoids, and cooling agents. However, the health effects of inhaling these compounds are still not well understood. Regular analytical control of e-liquids and aerosols is crucial to gain valuable insights into e-liquid composition, generating new compounds during aerosolization, and the potential impact on human health. This work presents an overview of the analytical techniques used for the qualitative and quantitative determination of e-liquid and aerosol compounds, including a description of the methods used for aerosol collection. Gas and liquid chromatography are the most used analytical techniques for compound determination, followed by nuclear magnetic resonance spectroscopy. Additionally, inductively coupled plasma-mass spectrometry and inductively coupled plasma-optical emission spectroscopy are the most frequently used analytical techniques for elemental determination in e-liquids and their aerosols.

Stability of Flavoring Chemicals in e-Cigarette Liquids: A Naturalistic Product Aging Study over 24 months

Flavoring chemicals commonly used in many consumer products, including pharmaceuticals, foods, and beverages, deteriorate over time. Flavoring chemicals are also common additives in e-cigarette liquid formulations, but their stability in vaping products has not been evaluated. Since e-cigarette liquids are exposed to varying environmental conditions during storage and use, we assessed the stabilities of 20 flavoring chemicals commonly used in vaping products, including benzaldehyde (cherry flavor), menthol (cooling flavor), and vanillin (vanilla flavor). We prepared reference e-cigarette liquids (reference solutions) containing individual flavorings and a mixed liquid with combined flavorings in a 55:45 (v/v) propylene glycol to vegetable glycerin solution. We also purchased 14 commercial e-cigarette liquids. Liquids were stored over 24 months in different temperatures (room and cold) and light exposure conditions (ambient light and dark). Gas chromatography/mass spectrometry techniques were used to measure the concentration of each flavoring chemical at the baseline and after 1, 3, 6, 12, and 24 months. We used a nontargeted approach to identify potential degradation byproducts. Using an air-liquid interface with bronchial epithelial cells and the Neutral Red assay, we also compared the cytotoxicity of selected reference solutions vaped at the baseline and after storage over 24 months. The flavorings in reference solutions stored at ambient temperature and exposed to light were the least stable. Reducing exposure to light and storing reference solutions in cold temperatures delayed the degradation of some flavorings. Tentatively identified byproducts of flavoring degradation found in unstable reference solutions suggested oxidation, hydrolysis, and condensation reactions with solvents. Despite substantial changes in the chemical composition, no significant cytotoxicity differences were detected between fresh and aged reference solutions. Our findings suggest that storing vaping products in dark places and at cold temperatures improves the stability of flavorings in e-cigarette liquids.

Role of the Transient Receptor Potential Ankyrin-1 in the Pulmonary, Vascular, and Systemic Effects of Short-Term Acrolein Inhalation in Mice: Implications for the Toxicity of Electronic Nicotine Delivery Systems

The cardiovascular and pulmonary disease risks of the use of electronic nicotine delivery systems (ENDS) are uncertain. We recently showed that ENDS solvent-derived aerosol (propylene glycol and vegetable glycerin, PG:VG) exposure induced a transient receptor potential ankyrin-1 (TRPA1)-dependent endothelial dysfunction (ED) in healthy female mice. As thermal degradation of PG:VG generates aldehydes, we hypothesized that acrolein (AC), a constituent of ENDS-derived aerosol and a known TRPA1 agonist, was responsible, in part, for the observed TRPA1-dependent pulmonary and vascular effects of PG:VG. To test this, female wild-type (WT) and TRPA1 null mice were exposed by inhalation to either filtered air or AC alone, and biomarkers of exposure and of harm were measured. Compared with their genotype-matched air control group, JUUL Virginia Tobacco (VT), PG:VG, and AC alone exposures (6 h) significantly increased urinary levels of the AC metabolite, 3-hydroxypropyl mercapturic acid (3HPMA), in both female WT and TRPA1 null mice. AC exposures at 1 and 3 ppm led to the rapid onset and reversal (upon cessation) of 'respiratory braking' in female WT but not in TRPA1 null mice indicating a TRPA1 dependence. As AC stimulated TRPA1-dependent respiratory braking, we measured urinary monoamines and their metabolites after exposure as a proxy of nervous system activation. In WT mice, AC exposure suppressed levels of dopamine, metanephrine, serotonin (5HT), and 5HT metabolite (5HIAA), whereas in TRPA1 null mice only 5HT was equally suppressed by AC. To assess vascular effects, mice were exposed for 4 days to Air or AC (6 h/day, 1 ppm), and aortic function was measured ex vivo. Although endothelial-dependent relaxation was similar in air control and AC-exposed mice, aortic sensitivity to an NO donor was enhanced significantly and equally by AC in both WT and TRPA1 null mice reflective of a TRPA1-independent and compensatory effect. Collectively, AC exposure at a level present in ENDS aerosols stimulated both TRPA1-dependent and -independent pulmonary, vascular, and systemic effects. These data suggest that ENDS use may increase cardiovascular and pulmonary disease risk, in part, via AC present in ENDS-derived aerosols yet independent of either nicotine or flavorants. The level of AC present in ENDS aerosols should be lowered to an amount where it does not induce biomarkers of vascular, pulmonary, and systemic harm to mitigate potential long-term disease risk.

Composition of e-cigarette aerosols: A review and risk assessment of selected compounds

The potential harms and benefits of e-cigarettes, or electronic nicotine delivery systems (ENDS), have received significant attention from public health and regulatory communities. Such products may provide a reduced risk means of nicotine delivery for combustible cigarette smokers while being inappropriately appealing to nicotine naive youth. Numerous authors have examined the chemical complexity of aerosols from various open- and closed-system ENDS. This body of literature is reviewed here, with the risks of ENDS aerosol exposure among users evaluated with a margin of exposure (MoE) approach for two non-carcinogens (methylglyoxal, butyraldehyde) and a cancer risk analysis for the carcinogen N-nitrosonornicotine (NNN). We identified 96 relevant papers, including 17, 13, and 5 reporting data for methylglyoxal, butyraldehyde, and NNN, respectively. Using low-end (minimum aerosol concentration, low ENDS use) and high-end (maximum aerosol concentration, high ENDS use) assumptions, estimated doses for methylglyoxal (1.78 × 10-3-135 μg/kg-bw/day) and butyraldehyde (1.9 × 10-4-66.54 μg/kg-bw/day) corresponded to MoEs of 227-17,200,000 and 271-280,000,000, respectively, using identified points of departure (PoDs). Doses of 9.90 × 10-6-1.99 × 10-4 μg/kg-bw/day NNN corresponded to 1.4-28 surplus cancers per 100,000 ENDS users, relative to a NNN-attributable surplus of 7440 per 100,000 cigarette smokers. It was concluded that methylglyoxal and butyraldehyde in ENDS aerosols, while not innocuous, did not present a significant risk of irritant effects among ENDS users. The carcinogenic risks of NNN in ENDS aerosols were reduced, but not eliminated, relative to concentrations reported in combustible cigarette smoke.

Nicotine Influence on Vascular and Neurocognitive Function with In-utero Electronic Cigarette Exposure

Emerging studies find arteriolar dysfunction in offspring with in-utero electronic cigarette (Ecig) exposure, but the long-term effect on offspring's cerebrovascular vascular and neurocognitive health is poorly understood. Ecigs provides a unique opportunity to directly evaluate the contributions of inhaled nicotine from the vehicle e-liquid - which was not possible with traditional cigarettes. Moreover, many Ecigs have variable power settings, which can alter the toxicity of the aerosol cloud produced. We hypothesize maternal vaping at different wattages will have variable effects on cerebrovascular function in the offspring, and that these effects would be independent of nicotine. We used time-mated female Sprague-Dawley rats with Ecig exposure from gestation day (GD)2-21. We studied male and female offspring for vascular and neurocognitive function at 1-, 3-, 6- and 12-months of age. We found that, both sexes, offspring with in-utero exposure (at 5w and 30w Ecig conditions) exhibited impaired middle cerebral artery (MCA) reactivity. While the magnitude of impairment was greater at higher that lower watts, Ecig at 5-watts still exhibited significant impairments in MCA function (suggesting the harm threshold for blood vessels is very low). Vascular dysfunction was evident with or without nicotine in the e-liquid, but nicotine exposure resulted in short-term memory deficits, evidence of neuronal damage, and increased astrocyte interaction with endothelial cells in 6- and 12-month-old offspring. We also observed altered expression of clock genes and antioxidant signaling pathways, along with a decrease in sirtuin-1 expression, decreased ratio of beta-amyloid Aβ 42/40 protein expression, and increased in NOX1, which are consistent with redox imbalance, neuroinflammation, and advancing cellular senescence. These preclinical data provide evidence suggesting that in utero exposure to Ecigs from maternal vaping can be expected to adversely affect the brain health of offspring in their adult life and that neurocognitive outcomes are worsened with exposure to nicotine.

Assessing the impact of device parameters on electronic cigarette aerosol dynamics: Comprehensive analysis of emission profiles and toxic chemical constituents

The toxicity of electronic cigarette (EC) aerosol is influenced not only by the type of e-liquid but also by various operational parameters of the device used to vaporize it. In this study, we utilized a flask and heating mantle system, instead of a conventional EC device, to systematically evaluate the effects of EC device operational parameters, including vaporization temperature, airflow rate, and the materials of coils and wicks, on the generated mass of EC aerosol and the production of toxic carbonyl compounds. The results demonstrated that these parameters significantly impact aerosol mass and toxicant composition. Specifically, increasing vaporization temperature and airflow rate drastically affect aerosol mass, showing exponential and logarithmic increases. Using the ISO 20768 method, aerosol mass (from 20 μL e-liquid) escalated over threefold from 3100 μg at 200°C to 10,300 μg at 400°C, illustrating temperature's pivotal role. Formaldehyde levels rose from 0.21 μg to 60.2 μg with temperature increases from 200°C to 400°C. At a realistic vaporization temperature of 300°C, the formaldehyde mass was 2.21 μg (3.28 ppm), exceeding the lowest-observed-adverse-effect level for acute respiratory toxicity in humans. While cotton wicks modestly affected aerosol mass, they significantly raised formaldehyde and acetaldehyde levels by 36.2%. In contrast, silica, kanthal, and nichrome materials increased aerosol mass and chemicals like propylene glycol, vegetable glycerin, nicotine, formaldehyde, and acetaldehyde by 22.7% to 63.2%. Our findings underscore the urgent need for regulations encompassing e-liquids and EC devices to mitigate health risks associated with EC use, providing a scientific basis for safety-focused regulatory measures.

E-Cigarette effects on oral health: A molecular perspective

Electronic cigarettes (e-cigarettes) have emerged as a potential alternative to traditional smoking and may aid in tobacco harm reduction and smoking cessation. E-cigarette use has notably increased, especially among young non-tobacco users, raising concerns due to the unknown long-term health effects. The oral cavity is the first and one of the most crucial anatomical sites for the deposition of e-cigarette aerosols. E-cigarette aerosols contain nicotine, flavors, volatile organic compounds, heavy metals, carcinogens, and other hazardous substances. These aerosols impact the oral cavity, disrupting host-microbial interactions and triggering gingivitis and systemic diseases. Furthermore, oral inflammation and periodontitis can be caused by proinflammatory cytokines induced by e-cigarette aerosols. The toxic components of e-cigarette aerosols increase the cellular reactive oxygen species (ROS) levels, reduce antioxidant capacity, increase DNA damage, and disrupt repair processes, which may further contribute to harmful effects on oral epithelum, leading to inflammatory and pre-malignant oral epithelial lesions. In this review, we analyze the toxicological properties of compounds in e-cigarette aerosols, exploring their cytotoxic, genotoxic, and inflammatory effects on oral health and delving into the underlying molecular mechanisms. Further research is essential to understand the impact of e-cigarettes on oral health and make informed regulatory decisions based on reliable scientific evidence.

The use of the model organism Caenorhabditis elegans in the investigation of the adverse effects of electronic cigarettes

The use of tobacco products is one of the most preventable risk factors for mortality from a variety of diseases, including cardiovascular, infectious, respiratory, and neoplastic conditions. The use of electronic cigarettes (ECIGs), also known as electronic nicotine delivery devices, has increased significantly in recent years. Nicotine, propylene glycol, and / or glycerine, water, alcohol, flavorings, and other substances are among the many chemicals found in ECIGs that are vaporized and inhaled. A review of the existing literature shows that research dedicated to ECIGs is a rapidly developing and growing field of study. The rationale for the use of ECIGs is that they represent a safer alternative to traditional tobacco products. However, vaping safety profiles are still under development, as this is a relatively recent phenomenon. Various model organisms can be employed to examine the cellular processes that may be altered by exposure to the electronic liquids utilized for vaping. For example, the translucent multicellular eukaryote Caenorhabditis elegans is widely used as a model organism to explain a broad range of biological processes, including aging, stress response, development, and many others. Due to its short lifespan and easy use, C. elegans is an ideal model organism for studying chronic exposure to drugs and environmental toxicology. This review presents a summary of the most recent findings on the impact of electronic cigarettes on the physiological health of this nematode. Preliminary observations made in C. elegans can provide insight into the consequences of exposure to fundamental cellular physiology, which can then be used for future research in humans and mammalian models.

E-cigarettes and arterial health: A review of the link between vaping and atherosclerosis progression

Recent studies have suggested an evolving understanding of the association between vaping, specifically electronic cigarette (e-cigarette) use, and the progression of atherosclerosis, a significant contributor to cardiovascular disease. Despite the prevailing perception of vaping as a safer alternative to traditional tobacco smoking, accumulating evidence suggests that the aerosols emitted by e-cigarettes contain harmful constituents that may promote endothelial dysfunction, oxidative stress, inflammation, and dyslipidemia-key mechanisms implicated in atherosclerosis pathogenesis. While past research, including experimental studies and clinical investigations, has shed light on the potential cardiovascular risks associated with vaping, gaps in knowledge persist. Future research endeavors should focus on interpreting the long-term effects of vaping on atherosclerosis development and progression, exploring the impact of different e-cigarette formulations and user demographics, and identifying effective strategies for mitigating the cardiovascular consequences of vaping. By identifying and addressing these research gaps, we can enhance our understanding of the cardiovascular implications of vaping and inform evidence-based interventions and policies to safeguard public health.

Effects of E-Cigarette (e-cig) Aerosols on Mutagenesis in Selected Organs in a C57 lacI (BigBlueTM) Mouse Model

The objective of this study is to investigate the potential mutagenic effects of the exposure of mice to aerosols produced from the component liquids of an electronic nicotine delivery system (ENDS). The use of electronic cigarettes (e-cigs) and ENDSs has increased tremendously over the past two decades. From what we know to date, ENDSs contain much lower levels of known carcinogens than tobacco smoke. While conventional tobacco smoke is a well-established mutagen, little is known about the mutagenicity of ENDS aerosols. Here, we report the mutagenic effects of a 3-month whole body exposure of C57 lacI mice (BigBlueTM) to filtered air (AIR) or ENDS aerosols in several tissues. Aerosols were generated from a 50/50 vegetable glycerin (VG)/propylene glycol (PG) mixture with and without nicotine. The results revealed that in the lung, bladder urothelial tissue, and tongue, mutagenesis was significantly greater in the VG/PG/nicotine group than in the AIR group. In all organs except the bladder, mutagenesis in the VG/PG only group was similar to those exposed to AIR. In the bladder, mutagenesis in the VG/PG group was elevated compared to that in the AIR group. In the liver, mutagenesis was modestly elevated in the VG/PG/nicotine group, but the elevation failed to reach statistical significance. Overall, there were no consistent differences in mutagenesis between the sexes. The results of this study suggest that exposure to e-cig aerosols containing nicotine represents a risk factor for carcinogenesis in several organ systems, and exposure to VG/PG alone may be a risk factor for bladder cancer.

The impact of electronic cigarette aerosol exposure on spatial memory formation: Modulation by orally administered vitamin E

The use of electronic cigarettes (ECIGs) has grown exponentially among young adolescents. Tobacco smoking, in general and ECIG use in particular, has been linked to disruption of the oxidative system, resulting in organ damage. The current investigation intends to evaluate if orally administered Vitamin E (VitE) can protect from learning and cognitive impairment induced by ECIG aerosol exposure in a rat model. This effect was determined by studying behavioral and molecular targets for potential learning and memory impairment. Adult Wistar rats were assigned to the following groups (N= 12/group): Control, ECIG, VitE, and VitE+ECIG. The animals in the groups ECIG and VitE+ECIG were exposed to ECIG aerosol (1 hr/day, 6 days/week) for four weeks. The control group and VitE group were exposed to fresh air. At the same time, the VitE group and VitE+ECIG group were given Vitamin E 100 mg/kg/ day via gavage for the same period as the exposure. The control group and ECIG group were given the vehicle via gavage. Behavioral assessment was performed using the Radial Arm Water Maze. In addition, molecular measures (BDNF, SOD, GPx, GSH, and GSSG), were measured in rats' hippocampal tissues. The results showed that VitE prevented ECIG aerosol exposure-induced impairment of spatial short-term and long-term memory formation (p<0.05), decreased BDNF, and activities/levels of GPx, SOD, and GSH (p<0.05). Moreover, VitE protected against GSSG levels increases (p<0.05) associated with ECIG aerosol exposure. In summary, exposure to ECIGs resulted in spatial memory impairments, which could be mitigated by orally administered vitamin E.

The biochemistry of the carcinogenic alcohol metabolite acetaldehyde

Acetaldehyde (AcH) is the first metabolite of ethanol and is proposed to be responsible for the genotoxic effects of alcohol consumption. As an electrophilic aldehyde, AcH can form multiple adducts with DNA and other biomolecules, leading to function-altering and potentially toxic and carcinogenic effects. In this review, we describe sources of AcH in humans, including AcH biosynthesis mechanisms, and outline the structures, properties and functions of AcH-derived adducts with biomolecules. We also describe human AcH detoxification mechanisms and discuss ongoing challenges in the field.

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.

Vaping causes an acute BMI-dependent change in pulmonary blood flow

Vaping use has skyrocketed especially among young adults, however there is no consensus on how vaping impacts the lungs. We aimed to determine whether there were changes in lung function acutely after a standard vaping session or if there were differences in lung function metrics between a healthy never-vaping cohort (N = 6; 27.3 ± 3.0 years) and a young asymptomatic vaping cohort (N = 14; 26.4 ± 8.0 years) indicating chronic changes. Pulmonary function measurements and impulse oscillometry were obtained on all participants. Oxygen-enhanced and Arterial Spin Labelling MRI were used to measure specific ventilation and perfusion, respectively, before and after vaping, and in the control cohort at baseline. MRI metrics did not show any significant differences in specific ventilation or perfusion after vaping. Heart rate increased post-vaping (68.1 ± 10.5 to 71.3 ± 8.7, p = 0.020); however, this and other metrics did not show a nicotine dose-dependent effect. There was a significant negative correlation between BMI and change in mean perfusion post-vaping (p = 0.003); those with normal/low BMI showing an increase in perfusion and vice versa for high BMI. This may be due to subjects lying supine during vaping inhalation. Pulmonary function metrics indicative of airways resistance showed significant differences between the vaping and control cohorts indicating early airway changes.

Formaldehyde and the transient receptor potential ankyrin-1 contribute to electronic cigarette aerosol-induced endothelial dysfunction in mice

Electronic nicotine delivery systems (ENDS) aerosol exposures can induce endothelial dysfunction (ED) in healthy young humans and animals. Thermal degradation of ENDS solvents, propylene glycol, and vegetable glycerin (PG: VG), generates abundant formaldehyde (FA) and other carbonyls. Because FA can activate the transient receptor potential ankyrin-1 (TRPA1) sensor, we hypothesized that FA in ENDS aerosols provokes TRPA1-mediated changes that include ED and "respiratory braking"-biomarkers of harm. To test this, wild-type (WT) and TRPA1-null mice were exposed by inhalation to either filtered air, PG: VG-derived aerosol, or FA (5 ppm). Short-term exposures to PG: VG and FA-induced ED in female WT but not in female TRPA1-null mice. Moreover, acute exposures to PG: VG and FA stimulated respiratory braking in WT but not in TRPA1-null female mice. Urinary metabolites of FA (ie, N-1,3-thiazolidine-4-carboxylic acid, TCA; N-1,3-thiazolidine-4-carbonyl glycine, TCG) and monoamines were measured by LC-MS/MS. PG: VG and FA exposures significantly increased urinary excretion of both TCA and TCG in both WT and TRPA1-null mice. To confirm that inhaled FA directly contributed to urinary TCA, mice were exposed to isotopic 13C-FA gas (1 ppm, 6 h). 13C-FA exposure significantly increased the urine level of 13C-TCA in the early collection (0 to 3 h) supporting a direct relationship between inhaled FA and TCA. Collectively, these data suggest that ENDS use may increase CVD risk dependent on FA, TRPA1, and catecholamines, yet independently of either nicotine or flavorants. This study supports that levels of FA in ENDS-derived aerosols should be lowered to mitigate CVD risk in people who use ENDS.

Influence of gestational window on offspring vascular health in rodents with in utero exposure to electronic cigarettes

Studies have shown cerebrovascular dysfunction in offspring with full-gestational electronic cigarette (Ecig) exposure, but little is known about how individual trimester exposure impacts offspring health. This study aimed to determine if there is a critical window during gestation that contributes to vascular and anxiety-like behavioural changes seen with full-term exposure. To test this, rats were time-mated, and the pregnant dams were randomly assigned to Ecig exposure during first trimester (gestational day, GD2-7), second trimester (GD8-14), third trimester (GD15-21) or full-term gestation (GD2-21). We also assessed the effect of maternal preconception exposure. Both male and female offspring from all maternal exposure conditions were compared to offspring from dams under ambient air (control) conditions. Ecig exposure consisted of 60-puffs/day (5 days/week) using either 5 or 30 watts for each respective exposure group. We found that maternal exposure to Ecig in the second and third trimesters resulted in a decrease (23-38%) in vascular reactivity of the middle cerebral artery (MCA) reactivity in 3- and 6-month-old offspring compared to Air offspring. Further, the severity of impairment was comparable to the full-term exposure (31-46%). Offspring also displayed changes in body composition, body mass, anxiety-like behaviour and locomotor activity, indicating that Ecigs influence neurodevelopment and metabolism. Maternal preconception exposure showed no impact on offspring body mass, anxiety-like behaviour, or vascular function. Thus, the critical exposure window where Ecig affects vascular development in offspring occurs during mid- to late-gestation in pregnancy, and both 5 W and 30 W exposure produce significant vascular dysfunction compared to Air. KEY POINTS: Exposure to electronic cigarettes (Ecigs) is known to increase risk factors for cardiovascular disease in both animals and humans. Maternal Ecig use during pregnancy in rodents is found to impair the vascular health of adolescent and adult offspring, but the critical gestation window for Ecig-induced vascular impairment is not known. This study demonstrates Ecig exposure during mid- and late-gestation (i.e. second or third trimester) results in impaired endothelial cell-mediated dilatation (i.e. middle cerebral artery reactivity) and alters anxiety-like behaviour in offspring. Maternal exposure prior to conception did not impact offspring's vascular or anxiety-like behavioural outcomes. Rodent models have been a reliable and useful predictor of inhalation-induced harm to humans. These data indicate maternal use of Ecigs during pregnancy should not be considered safe, and begin to inform clinicians and women about potential long-term harm to their offspring.

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.

Pancreatic Cancer: A Review of Risk Factors

Pancreatic adenocarcinoma is one of the most lethal types of gastrointestinal cancer despite the latest medical advances. Its incidence has continuously increased in recent years in developed countries. The location of the pancreas can result in the initial symptoms of neoplasia being overlooked, which can lead to a delayed diagnosis and a subsequent reduction in the spectrum of available therapeutic options. The role of modifiable risk factors in pancreatic cancer has been extensively studied in recent years, with smoking and alcohol consumption identified as key contributors. However, the few screening programs that have been developed focus exclusively on genetic factors, without considering the potential impact of modifiable factors on disease occurrence. Thus, fully understanding and detecting the risk factors for pancreatic cancer represents an important step in the prevention and early diagnosis of this type of neoplasia. This review reports the available evidence on different risk factors and identifies the areas that could benefit the most from additional studies.

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

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

Challenges in current inhalable tobacco toxicity assessment models: A narrative review

Emerging tobacco products such as electronic nicotine delivery systems (ENDS) and heated tobacco products (HTPs) have a dynamic landscape and are becoming widely popular as they claim to offer a low-risk alternative to conventional smoking. Most pre-clinical laboratories currently exploit in vitro, ex vivo, and in vivo experimental models to assess toxicological outcomes as well as to develop risk-estimation models. While most laboratories have produced a wide range of cell culture and mouse model data utilizing current smoke/aerosol generators and standardized puffing profiles, much variation still exists between research studies, hindering the generation of usable data appropriate for the standardization of these tobacco products. In this review, we discuss current state-of-the-art in vitro and in vivo models and their challenges, as well as insights into risk estimation of novel products and recommendations for toxicological parameters for reporting, allowing comparability of the research studies between laboratories, resulting in usable data for regulation of these products before approval by regulatory authorities.

Rates of adverse events and related risk factors following e-cigarette use

BACKGROUND

E-cigarettes have emerged as popular products, especially for younger populations. However, concerns regarding health effects exist and there is a notable gap in understanding the prevalence and nature of adverse events. This study aims to examine the rate of adverse events in individuals who use e-cigarettes in a large sample.

METHODS

A cross-sectional survey was conducted with a sample of 4695 current and former e-cigarette users with a median age of 34 years. The survey collected data on e-cigarette use, adverse events experienced, product characteristics, related behaviors, sociodemographic factors and presence of medical comorbidities. Statistical analyses were conducted using Pearson's chi-squared tests and logistic regression.

RESULTS

A total of 78.9% of respondents reported experiencing an adverse event within 6 h of using a vaping device, with the most common events being headache, anxiety and coughing. Product characteristics and related behaviors significantly influenced the risk of adverse events. There were also sociodemographic disparities, with Hispanic respondents and those with at least college-level education reporting higher rates of adverse events.

CONCLUSIONS

Our study found a high rate of adverse events among e-cigarette users. We identified that certain e-cigarette product characteristics, behaviors and medical comorbidities significantly increased the risk of these events.

Addressing Cardiovascular Toxicity Risk of Electronic Nicotine Delivery Systems in the Twenty-First Century: "What Are the Tools Needed for the Job?" and "Do We Have Them?"

Cigarette smoking is positively and robustly associated with cardiovascular disease (CVD), including hypertension, atherosclerosis, cardiac arrhythmias, stroke, thromboembolism, myocardial infarctions, and heart failure. However, after more than a decade of ENDS presence in the U.S. marketplace, uncertainty persists regarding the long-term health consequences of ENDS use for CVD. New approach methods (NAMs) in the field of toxicology are being developed to enhance rapid prediction of human health hazards. Recent technical advances can now consider impact of biological factors such as sex and race/ethnicity, permitting application of NAMs findings to health equity and environmental justice issues. This has been the case for hazard assessments of drugs and environmental chemicals in areas such as cardiovascular, respiratory, and developmental toxicity. Despite these advances, a shortage of widely accepted methodologies to predict the impact of ENDS use on human health slows the application of regulatory oversight and the protection of public health. Minimizing the time between the emergence of risk (e.g., ENDS use) and the administration of well-founded regulatory policy requires thoughtful consideration of the currently available sources of data, their applicability to the prediction of health outcomes, and whether these available data streams are enough to support an actionable decision. This challenge forms the basis of this white paper on how best to reveal potential toxicities of ENDS use in the human cardiovascular system-a primary target of conventional tobacco smoking. We identify current approaches used to evaluate the impacts of tobacco on cardiovascular health, in particular emerging techniques that replace, reduce, and refine slower and more costly animal models with NAMs platforms that can be applied to tobacco regulatory science. The limitations of these emerging platforms are addressed, and systems biology approaches to close the knowledge gap between traditional models and NAMs are proposed. It is hoped that these suggestions and their adoption within the greater scientific community will result in fresh data streams that will support and enhance the scientific evaluation and subsequent decision-making of tobacco regulatory agencies worldwide.

Impact of Electronic Cigarette use on Cardiovascular Health: Current Evidence, Causal Pathways, and Public Health Implications

Electronic cigarette (e-cigarette) use is increasing in Europe and the USA. While mounting evidence exists regarding an array of associated adverse health effects, to date limited evidence exists regarding the health effects of e-cigarette use on cardiovascular (CV) disease (CVD). The present review summarizes the effects of e-cigarette use on CV health. A search strategy of in vivo experimental, observational studies (including population-based cohort studies), and interventional studies was conducted in PubMed, MEDLINE, and Web of Science (April 1, 2009-April 1, 2022). The main findings revealed that the influence of e-cigarette on health are attributed mainly to the individual and interactive effects of flavors and additives used in e-cigarette fluids, along with the extended heating. The above collectively stimulate prolonged sympathoexcitatory CV autonomic effects, such as increased heart rate and diastolic blood pressure (BP), as well as decreased oxygen saturation. Hence, e-cigarette users are at increased risk of developing atherosclerosis, hypertension, arrhythmia, myocardial infarction, and heart failure. Such risks are anticipated to increase, especially among the young who are increasingly adopting e-cigarette use particularly with flavored additives. Further investigations are urgently needed to evaluate the long-term effects of e-cigarette use, particularly among susceptible population groups such as youth.

Unveiling the Impact of Electronic Cigarettes (EC) on Health: An Evidence-Based Review of EC as an Alternative to Combustible Cigarettes

Cigarette smoking has been considered a major public health concern due to its serious impact on health. However, smokers intending to quit may find long-term abstinence challenging. When smoking an electronic cigarette (EC), users can experience a sensation and taste similar to that of smoking a combustible cigarette. Therefore, manufacturers promote these products as a viable substitute for combustible cigarettes. However, several researchers report the serious health impacts experienced by EC users. Therefore, this review aims to examine the health impacts of EC use. Based on the findings of the research papers reported in the literature, the role of EC as a smoking cessation tool is unclear. Several researchers have also reported a significant association between EC usage among non-smokers at baseline and the future initiation of combustible cigarette smoking. EC use significantly impacts user health. The nicotine that is present in EC e-liquids can elevate blood pressure, resulting in blood vessel constriction and an increase in heart rate, ultimately leading the body to an ischemic condition, resulting in myocardial infarction (MI), stroke, and increased arterial stiffness. Researchers report a higher likelihood of prediabetes among EC users; its usage was associated with higher OR of having asthma attacks and higher OR of reporting depression and has an impact on birth outcomes among pregnant women. Men using EC are more likely to report erectile dysfunction than non-users. EC also has a significant impact on oral health, which includes periodontal diseases, mucosal lesions, irritation in the mouth and throat, reduced salivary flow, and an increased risk of developing cancer. The physical injury resulting from exploding EC is another health concern. The frequently burned areas included the hands, face, genitalia, and thighs. Marketers promote EC as an alternative to combustible cigarettes and a tool for quitting smoking. However, the Food and Drug Administration has not approved them for smoking cessation. EC can have a serious impact on the health of their users; hence, the findings of this paper have several implications, including the need for regulation of the sales and marketing of these products and educating the users on the impact of these products on their health and safety.

Particulate matter in aerosols produced by two last generation electronic cigarettes: a comparison in a real-world environment

The design of e-cigarettes (e-cigs) is constantly evolving and the latest models can aerosolize using high-power sub-ohm resistance and hence may produce specific particle concentrations. The aim of this study was to evaluate the aerosol characteristics generated by two different types of electronic cigarette in real-world conditions, such as a sitting room or a small office, in number of particles (particles/cm3). We compared the real time and time-integrated measurements of the aerosol generated by the e-cigarette types Just Fog and JUUL. Real time (10s average) number of particles (particles/cm3) in 8 different aerodynamic sizes was measured using an optical particle counter (OPC) model Profiler 212-2. Tests were conducted with and without a Heating, Ventilating Air Conditioning System (HVACS) in operation, in order to evaluate the efficiency of air filtration. During the vaping sessions the OPC recorded quite significant increases in number of particles/cm3. The JUUL e-cig produced significantly lower emissions than Just Fog with and without the HVACS in operation. The study demonstrates the rapid volatility or change from liquid or semi-liquid to gaseous status of the e-cig aerosols, with half-life in the order of a few seconds (min. 4.6, max 23.9), even without the HVACS in operation. The e-cig aerosol generated by the JUUL proved significantly lower than that generated by the Just Fog, but this reduction may not be sufficient to eliminate or consistently reduce the health risk for vulnerable non e-cig users exposed to it.

Impact of electronic cigarettes on pediatric, adolescent and young adult leukemia patients

Electronic cigarettes, which deliver an aerosolized, nicotine-containing product upon inhalation, are a public health issue that continue to gain popularity among adolescents and young adults in the United States. Use of electronic cigarettes is wide, and extends to pediatric patients with multiple comorbidities, including childhood cancer, leaving them vulnerable to further negative health outcomes. Acute leukemias are the most common type of cancer in pediatric populations, and treatment outcomes for these patients are improving; consequently, there is an increased emphasis on the effect of behavioral lifestyle factors on quality of life in survivorship. The rate of electronic cigarette use is higher among pediatric patients with a history of cancer than those without a history of cancer. Because electronic cigarettes are relatively new, much about their acute and long-term consequences remains unknown, as is their effect on therapy outcomes and long-term survivorship. This review article summarizes current knowledge about electronic cigarettes, including their composition and the trends in use among pediatric patients. Furthermore, this review provides a comprehensive description of the impact electronic cigarettes have on leukemia development, treatment and survivorship and highlights gaps in knowledge that will be necessary for developing recommendations, management strategies, and tailored treatments for pediatric leukemia patients and survivors who use these nicotine products.

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

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

In vitro toxicological evaluation of aerosols generated by a 4th generation vaping device using nicotine salts in an air-liquid interface system

BACKGROUND

Electronic cigarettes (EC) have gained popularity, especially among young people, with the introduction of fourth-generation devices based on e-liquids containing nicotine salts that promise a smoother vaping experience than freebase nicotine. However, the toxicological effects of nicotine salts are still largely unknown, and the chemical diversity of e-liquids limits the comparison between different studies to determine the contribution of each compound to the cytotoxicity of EC aerosols. Therefore, the aim of this study was to evaluate the toxicological profile of controlled composition e-liquid aerosols to accurately determine the effects of each ingredient based on exposure at the air-liquid interface.

METHODS

Human lung epithelial cells (A549) were exposed to undiluted aerosols of controlled composition e-liquids containing various ratios of propylene glycol (PG)/vegetable glycerin (VG) solvents, freebase nicotine, organic acids, nicotine salts, and flavoured commercial e-liquids. Exposure of 20 puffs was performed at the air-liquid interface following a standard vaping regimen. Toxicological outcomes, including cytotoxicity, inflammation, and oxidative stress, were assessed 24 h after exposure.

RESULTS

PG/VG aerosols elicited a strong cytotoxic response characterised by a 50% decrease in cell viability and a 200% increase in lactate dehydrogenase (LDH) production, but had no effects on inflammation and oxidative stress. These effects occurred only at a ratio of 70/30 PG/VG, suggesting that PG is the major contributor to aerosol cytotoxicity. Both freebase nicotine and organic acids had no greater effect on cell viability and LDH release than at a 70/30 PG/VG ratio, but significantly increased inflammation and oxidative stress. Interestingly, the protonated form of nicotine in salt showed a stronger proinflammatory effect than the freebase nicotine form, while benzoic acid-based nicotine salts also induced significant oxidative stress. Flavoured commercial e-liquids was found to be cytotoxic at a threshold dose of ≈ 330 µg/cm².

CONCLUSION

Our results showed that aerosols of e-liquids consisting only of PG/VG solvents can cause severe cytotoxicity depending on the concentration of PG, while nicotine salts elicit a stronger pro-inflammatory response than freebase nicotine. Overall, aerosols from fourth-generation devices can cause different toxicological effects, the nature of which depends on the chemical composition of the e-liquid.

Utilizing primary human airway mucociliary tissue cultures to model ramifications of chronic E-cigarette usage

Electronic cigarettes are battery powered devices that use a vape-liquid to produce a vapor that is inhaled. A consequence of the rise in e-cigarette usage was the 2019 emergence of a vaping-induced respiratory disease denoted as 'e-cigarette or vaping use-associated lung injury' (EVALI). One of the suspected causes of EVALI is Vitamin E Acetate (VEA), which was found to be a diluent in certain illicit vape-pens, whereas nicotine is commonly diluted in equal parts propylene glycol and vegetable glycerin (PG:VG). The prevalent use of e-cigarettes and the emergence of a novel illness has made understanding how e-cigarette vapors affect our respiratory tissues a public health concern. We have designed and produced a simple device that can operate e-cigarettes and deliver the vapor to a chamber containing a standard cell culture multi-well plate. Here we utilize our device to model the response of human airway mucociliary tissue after chronic exposure to vapors produced from either PG:VG or VEA. We note several differences between how PG:VG and VEA vapors interact with and alter airway tissue cultures and suggest potential mechanisms for how VEA-vapors can exacerbate EVALI symptoms. Our device combined with primary human airway tissue cultures make an economical and compact model system that allows for animal-free investigations into the acute and chronic consequences of e-cigarette vapors on primary respiratory cells.

Lung cancer in patients who have never smoked - an emerging disease

Lung cancer is the most common cause of cancer-related deaths globally. Although smoking-related lung cancers continue to account for the majority of diagnoses, smoking rates have been decreasing for several decades. Lung cancer in individuals who have never smoked (LCINS) is estimated to be the fifth most common cause of cancer-related deaths worldwide in 2023, preferentially occurring in women and Asian populations. As smoking rates continue to decline, understanding the aetiology and features of this disease, which necessitate unique diagnostic and treatment paradigms, will be imperative. New data have provided important insights into the molecular and genomic characteristics of LCINS, which are distinct from those of smoking-associated lung cancers and directly affect treatment decisions and outcomes. Herein, we review the emerging data regarding the aetiology and features of LCINS, particularly the genetic and environmental underpinnings of this disease as well as their implications for treatment. In addition, we outline the unique diagnostic and therapeutic paradigms of LCINS and discuss future directions in identifying individuals at high risk of this disease for potential screening efforts.

Conventional and multi-omics assessments of subacute inhalation toxicity due to propylene glycol and vegetable glycerin aerosol produced by electronic cigarettes

Propylene glycol (PG) and vegetable glycerin (VG) are the most common solvents used in electronic cigarette liquids. No long-term inhalation toxicity assessments have been performed combining conventional and multi-omics approaches on the potential respiratory effects of the solvents in vivo. In this study, the systemic toxicity of aerosol generated from a ceramic heating coil-based e-cigarette was evaluated. First, the aerosol properties were characterized, including carbonyl emissions, the particle size distribution, and aerosol temperatures. To determine toxicological effects, rats were exposed, through their nose only, to filtered air or a propylene glycol (PG)/ glycerin (VG) (50:50, %W/W) aerosol mixture at the target concentration of 3 mg/L for six hours daily over a continuous 28-day period. Compared with the air group, female rats in the PG/VG group exhibited significantly lower body weights during both the exposure period and recovery period, and this was linked to a reduced food intake. Male rats in the PG/VG group also experienced a significant decline in body weight during the exposure period. Importantly, rats exposed to the PG/VG aerosol showed only minimal biological effects compared to those with only air exposure, with no signs of toxicity. Moreover, the transcriptomic, proteomic, and metabolomic analyses of the rat lung tissues following aerosol exposure revealed a series of candidate pathways linking aerosol inhalation to altered lung functions, especially the inflammatory response and disease. Dysregulated pathways of arachidonic acids, the neuroactive ligand-receptor interaction, and the hematopoietic cell lineage were revealed through integrated multi-omics analysis. Therefore, our integrated multi-omics approach offers novel systemic insights and early evidence of environmental-related health hazards associated with an e-cigarette aerosol using two carrier solvents in a rat model.

E-cigarette vapor renders neutrophils dysfunctional due to filamentous actin accumulation

BACKGROUND

Electronic cigarette (e-cigarette) use continues to rise despite concerns of long-term effects, especially the risk of developing lung diseases such as chronic obstructive pulmonary disease. Neutrophils are central to the pathogenesis of chronic obstructive pulmonary disease, with changes in phenotype and function implicated in tissue damage.

OBJECTIVE

We sought to measure the impact of direct exposure to nicotine-containing and nicotine-free e-cigarette vapor on human neutrophil function and phenotype.

METHODS

Neutrophils were isolated from the whole blood of self-reported nonsmoking, nonvaping healthy volunteers. Neutrophils were exposed to 40 puffs of e-cigarette vapor generated from e-cigarette devices using flavorless e-cigarette liquids with and without nicotine before functions, deformability, and phenotype were assessed.

RESULTS

Neutrophil surface marker expression was altered, with CD62L and CXCR2 expression significantly reduced in neutrophils treated with e-cigarette vapor containing nicotine. Neutrophil migration to IL-8, phagocytosis of Escherichia coli and Staphylococcus aureus pHrodo bioparticles, oxidative burst response, and phorbol 12-myristate 13-acetate-stimulated neutrophil extracellular trap formation were all significantly reduced by e-cigarette vapor treatments, independent of nicotine content. E-cigarette vapor induced increased levels of baseline polymerized filamentous actin levels in the cytoplasm, compared with untreated controls.

CONCLUSIONS

The significant reduction in effector neutrophil functions after exposure to high-power e-cigarette devices, even in the absence of nicotine, is associated with excessive filamentous actin polymerization. This highlights the potentially damaging impact of vaping on respiratory health and reinforces the urgency of research to uncover the long-term health implications of e-cigarettes.

Association between e-cigarette use and myocardial infarction: a systematic review and meta-analysis

BACKGROUND

The popularity of e-cigarettes has risen dramatically over the last few years, particularly among the younger population. Although the use of combustible cigarettes has established evidence to be associated with the development of several adverse cardiopulmonary diseases, the investigations regarding the prospective long-term effects of e-cigarette use on the cardiovascular system have just begun. We set to investigate if there is an association between the history of MI and e-cigarette use among smokers and non-smokers?

METHODS

The current review aims to assess the association of myocardial infarction with e-cigarette consumption. PubMed, Google Scholar, and Cochrane Central Register of Controlled Trials (CENTRAL) were queried up to October 2022 to identify articles assessing the incidence of myocardial infarction among e-cigarette users. Data were meta-analyzed using a random-effects model to derive odds ratios (OR) and 95% confidence intervals.

RESULTS

Nine studies involving 984,764 patients were included. The mean age of e-cigarette smokers was less than the controls, and female participants dominated the sample size. E-cigarette users were associated with increased odds of MI than non-users [OR = 1.44; 95% CI (1.22, 1.74); P < 0.0001]. Dual users were also associated with increased odds of MI with large effect when compared to non-users [OR = 4.04; 95% CI (3.40, 4.81); P < 0.00001].

CONCLUSIONS

Dual use is associated with an increased risk of MI than e-cigarette use only. Similarly, dual and solely e-cigarette consumption patterns of nicotine delivery are at a higher risk of MI than non-smokers.

E-Cigarettes and Associated Health Risks: An Update on Cancer Potential

The potential cancer risk associated with electronic-cigarette (e-cigarette) use is ongoing and remains a subject of debate. E-Cigarettes work by heating a liquid that usually contains nicotine, flavorings, and other chemicals. When the liquid is heated, users inhale an aerosol into their lungs. While e-cigarettes are generally considered less harmful than traditional tobacco products, they still contain potentially harmful chemicals, which can damage DNA and lead to cancer. Several studies have investigated the potential cancer risk associated with e-cigarette use, while other studies have suggested that e-cigarette aerosol may contain carcinogenic chemicals that could increase the risk of lung and bladder cancer in humans. However, these studies are limited in their scope and do not provide conclusive evidence. Overall, the long-term cancer risk associated with e-cigarette use remains uncertain, more research is needed to fully understand the potential risks and benefits of e-cigarettes. However, this review will allow the investigator to get more recent updates about e-cigarettes.

Use of real-time monitors to evaluate the potential exposure of secondhand electronic cigarette particulate matter inside vehicles

Electronic cigarette (ECIG) use continues to be highly prevalent, especially among youth and young adults. Potential exposure from secondhand ECIG particulate matter (PM) places bystanders in danger of inhaling harmful substances, especially in confined spaces. This study was conducted to measure the potential exposure from secondhand ECIG PM exposure in vehicles, with participants completing a 30-min ECIG use session in their own vehicle with their preferred ECIG device. Sessions included a 5-min, 10-puff directed bout (30-s interpuff interval), followed by a 25-min ad libitum bout in which participants could take as many puffs as desired. Real-time PM1, PM2.5, and PM10 (the 50% efficiency mass cut-off of that passes through a size-selective inlet at 1 μm, 2.5 μm, and 10 μm aerodynamic diameters, respectively) measurements were captured during the sessions using portable PM monitors (MiniWRAS, pDR, SidePak, and GeoAir2 low-cost monitors). A total of 56 participants with valid measurements were included in the study, with a total of 13 unique ECIG device brands, including Vuse Alto, Box Air Bar, ElfBar, Esco Bar, Aegis Legend, Hyde Edge, JUUL, Kang Onee Stick, Kang Onee Stick Plus, Nord X, Nord 2, Nord 3, and Vaporesso. During the 5-min directed bout, the highest real-time PM2.5 mean concentrations were 175 μg/m3 for the MiniWRAS, 1050 μg/m3 for pDR and 3314 μg/m3 for SidePak. The filter measurements were not detectable in most experiments, except for two participants, with one taking 205 puffs and the other taking 285 puffs, approximately 10 times the mean (30) puffs of all participants. The evaluation of GeoAir2 with the MiniWRAS showed a wide range of Pearson correlation coefficient (r) values, ranging from -0.03 to 1.00, for the 13 ECIG brands. The mass median diameter (0.31 μm-3.42 μm) and geometric standard deviation (2.47-8.21) were different based on the participants for the same ECIG brand.

PM1 exposure and spatial transmission of nicotine from the simulated second-hand vapor of pod-based electronic cigarettes

Electronic cigarettes (E-cigarettes) have gained significant popularity in recent years as a substitute for combustible cigarettes. However, there is growing concern regarding the safety of E-cigarette products for both the users and those exposed passively to second-hand emissions, which contain nicotine and other toxic substances. In particular, the characteristics of second-hand PM1 exposure and the transmission of nicotine from E-cigarettes remain unclear. In this study, the untrapped mainstream aerosols from the E-cigarette and smoke from cigarettes were exhausted by the smoking machines which were operated under standardized puffing regimes to simulate second-hand vapor or smoke exposure. The concentrations and components of PM1 released from cigarettes and E-cigarettes were compared under varying environmental conditions and regulated using a heating, ventilation, and air conditioning (HVAC) system. Additionally, the ambient nicotine concentrations and the size distribution of the generated aerosols were determined at different distances from the release source. Results showed that PM1 accounted for the highest proportion (98 %) of the released particulate matter (PM1, PM2.5, and PM10). The mass median aerodynamic diameter (MMAD) of cigarette smoke (0.5 ± 0.01 μm, geometric standard deviation (GSD) 1.97 ± 0.1) was smaller than that of E-cigarette aerosols (1.06 ± 0.14 μm, GSD 1.79 ± 0.19). The PM1 concentrations and chemical components were effectively reduced when the HVAC system was utilized. Nicotine concentrations in E-cigarette aerosols were comparable to those of combustible cigarette emissions when close to the exposure source (0 m), while they declined more rapidly than cigarette smoke emissions with increasing distance from the source. Furthermore, the maximum nicotine concentrations occurred in 1 μm and 0.5 μm particles in E-cigarette and cigarette emissions, respectively. These results provide a scientific basis for the assessment of E-cigarette and cigarette aerosol passive exposure risks, guiding the development of environmental and human health control measures for these products.

Clinical impact of vaping on cardiopulmonary function and lung cancer development: an update

The word 'vaping' is used to define the usage of electronic cigarettes or other instruments to inhale a wide variety of heated and aerosolized substances. Although proposed as a less dangerous and oncogenic alternative than standard nicotine products, e-cigarettes and vaping devices are quite far from being considered benign. In fact, although vaping devices do not generate carcinogenic agents as polycyclic aromatic hydrocarbons produced by the combustion of standard cigarettes and their liquids do not present tobacco-related carcinogens like nitrosamines, there is nowadays clear evidence that they produce dangerous products during their use. Several different molecular mechanisms have been proposed for the oncogenic impact of vaping fluids - by means of their direct chemical action or derivative products generated by pyrolysis and combustion ranging from epithelial-mesenchymal transition, redox stress and mitochondrial toxicity to DNA breaks and fragmentation. In this review we focus on vaping devices, their potential impact on lung carcinogenesis, vaping-associated lung injury and other clinical implications on cardiovascular, cerebrovascular and respiratory diseases, as well as on the psychological implication of e-cigarettes both on heavy smokers trying to quit smoking and on younger non-smokers approaching vaping devices because they are considered as a less dangerous alternative to tobacco cigarettes.

Mechanisms of E-Cigarette Vape-Induced Epithelial Cell Damage

E-cigarette use has been reported to affect cell viability, induce DNA damage, and modulate an inflammatory response resulting in negative health consequences. Most studies focus on oral and lung disease associated with e-cigarette use. However, tissue damage can be found in the cardio-vascular system and even the bladder. While the levels of carcinogenic compounds found in e-cigarette aerosols are lower than those in conventional cigarette smoke, the toxicants generated by the heat of the vaping device may include probable human carcinogens. Furthermore, nicotine, although not a carcinogen, can be metabolized to nitrosamines. Nitrosamines are known carcinogens and have been shown to be present in the saliva of e-cig users, demonstrating the health risk of e-cigarette vaping. E-cig vape can induce DNA adducts, promoting oxidative stress and DNA damage and NF-kB-driven inflammation. Together, these processes increase the transcription of pro-inflammatory cytokines. This creates a microenvironment thought to play a key role in tumorigenesis, although it is too early to know the long-term effects of vaping. This review considers different aspects of e-cigarette-induced cellular changes, including the generation of reactive oxygen species, DNA damage, DNA repair, inflammation, and the possible tumorigenic effects.

Chemical analysis of selected harmful and potentially harmful constituents and in vitro toxicological evaluation of leading flavoured e-cigarette aerosols in the Chinese market

Use of electronic cigarettes (e-cigarettes) has increased significantly over the past decade due to consumer perception that these products represent a less risky alternative to combustible cigarettes. E-liquids generally contain a simple mix of vegetable glycerin, propylene glycerol, nicotine, organic acids, and flavourings. Regulators require that harmful and potentially harmful constituents (HPHCs) that might cause harm to the consumer must be monitored in the aerosol generated by e-cigarettes and in cigarette smoke (CS). To quantify HPHCs in aerosols from commercial flavoured e-cigarettes in Chinese market, this study has systematically compared levels of HPHCs, including eight carbonyls, five volatile organic compounds, four tobacco-specific nitrosamines, 16 polycyclic aromatic hydrocarbons, and seven heavy metals, in the aerosols of four market-leading flavoured e-cigarettes and mainstream CS, alongside in vitro cytotoxicity and mutagenicity assays. The vast majority of HPHCs were either undetected or significantly lower in the e-cigarette aerosols than in commercial CS or reference CS (3R4F). Where HPHCs were detected, there were small variations among the different flavoured e-cigarettes. In the neutral red uptake and Ames assays, aqueous extracts of the e-cigarette aerosols did not induce obvious cytotoxicity or mutagenicity, whereas CS aqueous extract showed dose-related cytotoxicity and mutagenicity. Collectively, these results indicate that use of e-cigarettes might potentially lead to a significant reduction in exposure to harmful substances, with fewer cytotoxic and mutagenic effects, as compared with conventional smoking. Further studies based on human puffing conditions and longer evaluation periods will be needed to substantiate this potential.

A review of the characteristic properties of selected tobacco chemicals and their associated etiological risks

OBJECTIVES

Despite the quantum of research findings on tobacco epidemic, a review on the formation characteristics of nicotine, aldehydes and phenols, and their associated etiological risks is still limited in literature. Accordingly, knowledge on the chemical properties and free radical formation during tobacco burning is an important subject towards unravelling the relationship between smoking behaviour and disease. This review investigates how scientific efforts have been advanced towards understanding the release of molecular products from the thermal degradation of tobacco, and harm reduction strategies among cigarette smokers in general. The mechanistic characteristics of nicotine and selected aldehydes are critically examined in this review. For the purpose of this work, articles published during the period 2004-2021 and archived in PubMed, Google Scholar, Medley, Cochrane, and Web of Science were used. The articles were selected based on the health impacts of cigarette smoking, tobacco burning kinetics, tobacco cessation and tobacco as a precursor for emerging diseases such as Covid-19.

CONTENT

The toxicity of cigarette smoke is directly correlated with its chemical composition derived from the pyrolysis of tobacco stem and leaves. Most of the harmful toxic substances are generated by pyrolysis during smoking and depends on pyrolysis conditions. Detailed studies have been conducted on the kinetics of nicotine by use of robust theoretical models in order to determine the rate constants of reactions in nicotine and those of nicotine dissociation via C-C and C-N scission, yielding pyridinyl and methyl radicals, respectively. Research has suggested that acetaldehyde enhances the effect of nicotine, which in turn reinforces addiction characteristics whereas acrolein and crotonaldehyde are ciliatoxic, and can inhibit lung clearance. On the other hand, phenol affects liver enzymes, lungs, kidneys, and the cardiovascular system while m-cresol attacks the nervous system.

SUMMARY AND OUTLOOK

The characteristics of chemical release during tobacco burning are very important in the tobacco industry and the cigarette smoking community. Understanding individual chemical formation from cigarette smoking will provide the necessary information needed to formulate sound tobacco reform policies from a chemical standpoint. Nonetheless, intense research is needed in this field in order to prescribe possible measures to deter cigarette smoking addiction and ameliorate the grave miseries bedevilling the tobacco smoking community.

Carcinogenic and non-carcinogenic health risk assessment of organic compounds and heavy metals in electronic cigarettes

E-cigarettes are now very popular in the world. Compared to traditional cigarettes, e-cigarettes are often considered safer and healthier. However, their safety remains controversial and requires further research and regulation. In this study, we aimed to understand the possible hazards to humans of four compounds (formaldehyde, acetaldehyde, acrolein, and acetone) and seven heavy metals (arsenic, cadmium, manganese, lead, copper, nickel, and chromium) contained in e-cigarette liquids and aerosols and perform a health risk assessment. We searched PubMed, CNKI, and other databases for relevant literature to obtain data on organic compounds and heavy metals in e-cigarette liquids and aerosols, and conducted acute, chronic, and carcinogenic risk assessments of various chemicals by different exposure routes. This study showed that exposure to four organic compounds and seven heavy metals in e-cigarette aerosols and e-liquids can cause varying levels of health risks in humans through different routes, with the inhalation route posing a higher overall risk than dermal exposure and oral intake. Various chemicals at high exposure doses can produce health risks beyond the acceptable range. E-cigarette designers must improve their products by changing the composition of the e-liquid and controlling the power of the device to reduce the health effects on humans.

Effect of glycerol concentration on levels of toxicants emissions from water-pipe tobacco smoking (WTS)

Glycerol, flavorings and sweeteners constitute approximately 70% of water-pipe tobacco smoking (WTS) mixtures. Tobacco mixture combustion produces smoke toxins (e.g. carbonyl compounds), of which the type and amount are highly dependable on tobacco mixture formula. While glycerol in tobacco mixture contribute to enhanced smoking experience, its' combustion produces toxicants such as acrolein. According to WHO, there are no approved international upper limits regulations on WTS ingredients. This study aims to assess toxicant emission levels corresponding to increasing glycerol concentration in WTS mixtures, which may aid in developing tobacco regulations towards harm reduction.MethodsLaboratory experimental study. Using laboratory water-pipe smoking machine, levels of toxicant emissions in the smoke from WTS mixture samples containing varying glycerol concentrations were measured using High-performance Liquid Chromatography (HPLC). Smoke from 5 consecutive smoking cycles with 35 puffs each (ISO 22486 standard) was led through a trapping system as described in the Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA) recommended method No. 74 (Determination of selected carbonyls in mainstream cigarette smoke by HPLC). Trapped carbonyls were then analysed by HPLC with a DAD detector.ResultsAcrolein emission is associated with glycerol addition in WTS mixture indicated by lab-made samples throughout all glycerol concentrations (10%, 20%, 40% and 60%), and brand samples with glycerol concentrations 10% to 20%. However, brand samples showed no increase in acrolein emission corresponding to the increase in glycerol concentrations from 20% to 60%.ConclusionThe effect of glycerol addition in waterpipe tobacco on acrolein emission varies between products. Tobacco fillers, additives and contents quality and other factors may affect toxicant emission levels. Therefore, regulatory recommendations towards defining upper limits of content concentrations require further investigations regarding potential confounders in acrolein emissions and health effects of market-available glycerol concentrations in waterpipe tobacco smoking.

Vaping, Environmental Toxicants Exposure, and Lung Cancer Risk

Lung cancer (LC) is the second-most prevalent tumor worldwide. According to the most recent GLOBOCAN data, over 2.2 million LC cases were reported in 2020, with an estimated new death incident of 1,796,144 lung cancer cases. Genetic, lifestyle, and environmental exposure play an important role as risk factors for LC. E-cigarette, or vaping, products (EVPs) use has been dramatically increasing world-wide. There is growing concern that EVPs consumption may increase the risk of LC because EVPs contain several proven carcinogenic compounds. However, the relationship between EVPs and LC is not well established. E-cigarette contains nicotine derivatives (e.g., nitrosnornicotine, nitrosamine ketone), heavy metals (including organometal compounds), polycyclic aromatic hydrocarbons, and flavorings (aldehydes and complex organics). Several environmental toxicants have been proven to contribute to LC. Proven and plausible environmental carcinogens could be physical (ionizing and non-ionizing radiation), chemicals (such as asbestos, formaldehyde, and dioxins), and heavy metals (such as cobalt, arsenic, cadmium, chromium, and nickel). Air pollution, especially particulate matter (PM) emitted from vehicles and industrial exhausts, is linked with LC. Although extensive environmental exposure prevention policies and smoking reduction strategies have been adopted globally, the dangers remain. Combined, both EVPs and toxic environmental exposures may demonstrate significant synergistic oncogenicity. This review aims to analyze the current publications on the importance of the relationship between EVPs consumption and environmental toxicants in the pathogenesis of LC.

Making Every Single Puff Count-Simple and Sensitive E-Cigarette Aerosol Sampling for GCxIMS and GC-MS Analysis

The analysis of the aerosol from tobaccoless electronic cigarettes (e-cigarettes) is an important part of understanding their impact on human health, yet sampling aerosol from e-cigarettes is still considered a challenge. It lacks a standard method for research and quality control and there are a variety of methods. However, few are simple and inexpensive, and none have been suggested for the use with gas chromatography coupled ion mobility spectrometry (GCxIMS). This work presents and evaluates such a setup made from standard lab equipment to quickly collect a quantitative sample from the aerosol of a single puff (5 s totaling 125 mL). The aerosol condensates directly in the cooled headspace (HS) vial, which is analyzed in the HS-GCxIMS or mass spectrometer (HS-GC-MS). The combined use of GC-MS and GCxIMS allows the simple and sensitive identification of unknown substances in complex mixtures and the identification of degradation products in the aerosols. A calibration of 26 flavor compounds (0.2-20 µg/g) was created using single puffs of a spiked, flavorless commercial refill solution and 2-alkanones as internal standards. This sensitive but easily reproducible setup enables a wide range of further investigations, even for labs that were previously unable to afford it.

Electronic nicotine delivery systems (ENDS): A convenient means of smoking?

Electronic nicotine delivery systems (ENDS), which are becoming increasingly popular in many parts of the world, have recently become more sophisticated in terms of their more active content and better controlled vaporisation. This review begins by describing how cigarette smoking led to the development of ENDS as a means of combatting nicotine addiction. ENDS are usually categorised as belonging to one of only three main generations, but a fourth has been added in order to differentiate the latest, most powerful, most advanced and innovative that have improved heating efficiency. Descriptions of the principal substances contained in ENDS are followed by considerations concerning the risk of toxicity due to the presence of albeit low concentrations of such a variety of compounds inhaled over a long time, and the increasingly widespread use of ENDS as a means of smoking illicit drugs. We also review the most widely used pharmacotherapeutic approaches to smoking cessation, and recent epidemiological data showing that ENDS can help some people to stop smoking. However, in order to ensure their appropriate regulation, there is a need for higher-quality evidence concerning the health effects and safety of ENDS, and their effectiveness in discouraging tobacco smoking.

The toxic effects of electronic cigarette aerosol and cigarette smoke on cardiovascular, gastrointestinal and renal systems in mice

Electronic cigarette (EC) has been suggested to be less harmful than cigarette smoking, but the research on the full extent of their harm reduction potential is still lacking. This study aimed to evaluate the influence of EC aerosol and cigarette smoke (CS) on cardiovascular, gastrointestinal, and renal functions in mice after prolonged exposure. Forty-eight C57BL/6J male mice were randomly grouped and then exposed to fresh air (control), mung bean-flavored EC aerosol with low and high dose (EC1L, 6 mg/kg; EC1H, 12 mg/kg), watermelon-flavored EC aerosol with low and high dose (EC2L, 6 mg/kg; EC2H, 12 mg/kg), and finally a cigarette smoke (CS, 6 mg/kg), respectively. After 10 weeks of exposure, the heart rate increased for both the EC and CS groups, and the effect of CS on blood oxygen saturation was significantly higher than that of the EC group (P < 0.01). Proteomic analysis of the heart tissue showed that the overlapped differential expression protein from the EC and CS exposures was Crip2. For the gastrointestinal system, oral mucosa was significantly damaged in CS group. Compare with CS, EC had significantly fewer negative effects on most of the indictors which focused on in this study.

Nicotine and Microvascular Responses in Skeletal Muscle from Acute Exposure to Cigarettes and Vaping

Despite claims of safety or harm reduction for electronic cigarettes (E-cig) use (also known as vaping), emerging evidence indicates that E-cigs are not likely safe, or necessarily safer than traditional cigarettes, when considering the user's risk of developing vascular dysfunction/disease. E-cigs are different from regular cigarettes in that E-cig devices are highly customizable, and users can change the e-liquid composition (such as the base solution, flavors, and nicotine level). Since the effects of E-cigs on the microvascular responses in skeletal muscle are poorly understood, we used intravital microscopy with an acute (one-time 10 puff) exposure paradigm to evaluate the individual components of e-liquid on vascular tone and endothelial function in the arterioles of the gluteus maximus muscle of anesthetized C57Bl/6 mice. Consistent with the molecular responses seen with endothelial cells, we found that the peripheral vasoconstriction response was similar between mice exposed to E-cig aerosol or cigarette smoke (i.e., 3R4F reference cigarette); this response was not nicotine dependent, and endothelial cell-mediated vasodilation was not altered within this acute exposure paradigm. We also report that, regardless of the base solution component [i.e., vegetable glycerin (VG)-only or propylene glycol (PG)-only], the vasoconstriction responses were the same in mice with inhalation exposure to 3R4F cigarette smoke or E-cig aerosol. Key findings from this work reveal that some component other than nicotine, in inhaled smoke or aerosol, is responsible for triggering peripheral vasoconstriction in skeletal muscle, and that regardless of one's preference for an E-cig base solution composition (i.e., ratio of VG-to-PG), the acute physiological response to blood vessels appears to be the same. The data suggest that vaping is not likely to be 'safer' than smoking towards blood vessels and can be expected to produce and/or result in the same adverse vascular health outcomes associated with smoking cigarettes.

Molecular insights into the role of electronic cigarettes in oral carcinogenesis

Electronic cigarette (EC) usage or vaping has seen a significant rise in recent years across various parts of the world. They have been publicized as a safe alternative to smoking; however, this is not supported strongly by robust research evidence. Toxicological analysis of EC liquid and aerosol has revealed presence of several toxicants with known carcinogenicity. Oral cavity is the primary site of exposure of both cigarette smoke and EC aerosol. Role of EC in oral cancer is not as well-researched as that of traditional smoking. However, several recent studies have shown that it can lead to a wide range of potentially carcinogenic molecular events in oral cells. This review delineates the oral carcinogenesis potential of ECs at the molecular level, providing a summary of the effects of EC usage on cancer therapy resistance, cancer stem cells (CSCs), immune evasion, and microbiome dysbiosis, all of which may lead to increased tumor malignancy and poorer patient prognosis. This review of literature indicates that ECs may not be as safe as they are perceived to be, however further research is needed to definitively determine their oncogenic potential.