ABSTRACT: BACKGROUND/OBJECTIVE:The heating of the fluids used in electronic cigarettes ("e-cigarettes") used to create "vaping" aerosols is capable of causing a wide range of degradation reaction products. We investigated formation of benzene (an important human carcinogen) from e-cigarette fluids containing propylene glycol (PG), glycerol (GL), benzoic acid, the flavor chemical benzaldehyde, and nicotine. METHODS/MAIN RESULTS:Three e-cigarette devices were used: the JUULTM "pod" system (provides no user accessible settings other than flavor cartridge choice), and two refill tank systems that allowed a range of user accessible power settings. Benzene in the e-cigarette aerosols was determined by gas chromatography/mass spectrometry. Benzene formation was ND (not detected) in the JUUL system. In the two tank systems benzene was found to form from propylene glycol (PG) and glycerol (GL), and from the additives benzoic acid and benzaldehyde, especially at high power settings. With 50:50 PG+GL, for tank device 1 at 6W and 13W, the formed benzene concentrations were 1.9 and 750 ?g/m3. For tank device 2, at 6W and 25W, the formed concentrations were ND and 1.8 ?g/m3. With benzoic acid and benzaldehyde at ~10 mg/mL, for tank device 1, values at 13W were as high as 5000 ?g/m3. For tank device 2 at 25W, all values were ?~100 ?g/m3. These values may be compared with what can be expected in a conventional (tobacco) cigarette, namely 200,000 ?g/m3. Thus, the risks from benzene will be lower from e-cigarettes than from conventional cigarettes. However, ambient benzene air concentrations in the U.S. have typically been 1 ?g/m3, so that benzene has been named the largest single known cancer-risk air toxic in the U.S. For non-smokers, chronically repeated exposure to benzene from e-cigarettes at levels such as 100 or higher ?g/m3 will not be of negligible risk.
Project description:Electronic cigarettes (e-cigarettes) generate an aerosol by heating a solution (e-liquid) with a metallic coil. Whether metals are transferred from the coil to the aerosol is unknown.Our goal was to investigate the transfer of metals from the heating coil to the e-liquid in the e-cigarette tank and the generated aerosol.We sampled 56 e-cigarette devices from daily e-cigarette users and obtained samples from the refilling dispenser, aerosol, and remaining e-liquid in the tank. Aerosol liquid was collected via deposition of aerosol droplets in a series of conical pipette tips. Metals were reported as mass fractions (?g/kg) in liquids and converted to mass concentrations (mg/m3) for aerosols.Median metal concentrations (?g/kg) were higher in samples from the aerosol and tank vs. the dispenser (all p<0.001): 16.3 and 31.2 vs. 10.9 for Al; 8.38 and 55.4 vs. <0.5 for Cr; 68.4 and 233 vs. 2.03 for Ni; 14.8 and 40.2 vs. 0.476 for Pb; and 515 and 426 vs. 13.1 for Zn. Mn, Fe, Cu, Sb, and Sn were detectable in most samples. Cd was detected in 0.0, 30.4, and 55.1% of the dispenser, aerosol, and tank samples respectively. Arsenic was detected in 10.7% of dispenser samples (median 26.7?g/kg) and these concentrations were similar in aerosol and tank samples. Aerosol mass concentrations (mg/m3) for the detected metals spanned several orders of magnitude and exceeded current health-based limits in close to 50% or more of the samples for Cr, Mn, Ni, and Pb.Our findings indicate that e-cigarettes are a potential source of exposure to toxic metals (Cr, Ni, and Pb), and to metals that are toxic when inhaled (Mn and Zn). Markedly higher concentrations in the aerosol and tank samples versus the dispenser demonstrate that coil contact induced e-liquid contamination. https://doi.org/10.1289/EHP2175.
Project description:Background E-cigarettes are the most popular aid to smoking cessation attempts in England and the USA. This research examined associations between e-cigarette device characteristics and patterns of use, tobacco-smoking relapse, and smoking abstinence. Methods A convenience sample of 371 participants with experience of vaping, and tobacco-smoking abstinence and/or relapse completed an online cross-sectional survey about e-cigarettes. Factors associated with smoking relapse were examined using multiple linear and logistic regression models. Results Most participants were self-reported long-term abstinent smokers (86.3%) intending to continue vaping. Most initiated e-cigarette use with a vape pen (45.8%) or cig-a-like (38.7%) before moving onto a tank device (89%). Due to missing data, managed through pairwise deletion, only around 70 participants were included in some of the main analyses. Those using a tank or vape pen appeared less likely to relapse than those using a cig-a-like (tank vs. cig-a-like OR?=?0.06, 95% CI 0.01–0.64, p?=?0.019). There was an inverse association between starting self-reported e-cigarette liquid nicotine concentration and relapse, interacting with device type (OR?=?0.79, 95% CI 0.63–0.99, p?=?0.047), suggesting that risk of relapse may have been greater if starting with a low e-cigarette liquid nicotine concentration and/or cig-a-like device. Participants reported moving from tobacco-flavored cig-a-likes to fruit/sweet/food flavors with tank devices. Conclusions Knowledge of how people have successfully maintained tobacco-smoking abstinence using vaping could help other tobacco smokers wishing to quit tobacco smoking through vaping.
Project description:BACKGROUND:Electronic cigarettes (e-cigarettes) have become popular, in part because they are perceived as a safer alternative to tobacco cigarettes. An increasing number of studies, however, have found toxic metals/metalloids in e-cigarette emissions. OBJECTIVE:We summarized the evidence on metal/metalloid levels in e-cigarette liquid (e-liquid), aerosols, and biosamples of e-cigarette users across e-cigarette device systems to evaluate metal/metalloid exposure levels for e-cigarette users and the potential implications on health outcomes. METHODS:We searched PubMed/TOXLINE, Embase®, and Web of Science for studies on metals/metalloids in e-liquid, e-cigarette aerosols, and biosamples of e-cigarette users. For metal/metalloid levels in e-liquid and aerosol samples, we collected the mean and standard deviation (SD) if these values were reported, derived mean and SD by using automated software to infer them if data were reported in a figure, or calculated the overall mean (mean ± SD) if data were reported only for separate groups. Metal/metalloid levels in e-liquids and aerosols were converted and reported in micrograms per kilogram and nanograms per puff, respectively, for easy comparison. RESULTS:We identified 24 studies on metals/metalloids in e-liquid, e-cigarette aerosols, and human biosamples of e-cigarette users. Metal/metalloid levels, including aluminum, antimony, arsenic, cadmium, cobalt, chromium, copper, iron, lead, manganese, nickel, selenium, tin, and zinc, were present in e-cigarette samples in the studies reviewed. Twelve studies reported metal/metalloid levels in e-liquids (bottles, cartridges, open wick, and tank), 12 studies reported metal/metalloid levels in e-cigarette aerosols (from cig-a-like and tank devices), and 4 studies reported metal/metalloid levels in human biosamples (urine, saliva, serum, and blood) of e-cigarette users. Metal/metalloid levels showed substantial heterogeneity depending on sample type, source of e-liquid, and device type. Metal/metalloid levels in e-liquid from cartridges or tank/open wicks were higher than those from bottles, possibly due to coil contact. Most metal/metalloid levels found in biosamples of e-cigarette users were similar or higher than levels found in biosamples of conventional cigarette users, and even higher than those found in biosamples of cigar users. CONCLUSION:E-cigarettes are a potential source of exposure to metals/metalloids. Differences in collection methods and puffing regimes likely contribute to the variability in metal/metalloid levels across studies, making comparison across studies difficult. Standardized protocols for the quantification of metal/metalloid levels from e-cigarette samples are needed. https://doi.org/10.1289/EHP5686.
Project description:INTRODUCTION:Tobacco product characteristics convey product attributes to potential users. This study aimed to assess independent contributions of specific e-cigarette and smokeless tobacco product characteristics to adolescents' perceptions about these products. METHODS:In 2019-2020, students (N=1003) attending a convenience sample of 7 high schools in California (USA) were individually randomized to one of two discrete choice experiments, featuring either electronic cigarettes (e-cigarettes) or moist snuff. Participants were presented like-product pairs of randomlygenerated hypothetical tobacco products differing in device type, flavor, vapor cloud, and nicotine amount (for e-cigarettes) or differing in brand, flavor, cut, and price (for moist snuff). Within pairs, participants were asked about which product they were more curious, was more dangerous, would give a greater 'buzz,' and would be easier to use. Conditional logistic regression was used to quantify independent associations of product characteristics to participants' choices. RESULTS:Each e-cigarette and moist snuff characteristic was independently associated with multiple product perceptions. All non-tobacco flavors were associated with more curiosity and perceived ease-of-use but lower perceived danger. Tank and pod-type e-cigarettes were viewed as easier to use and garnered more curiosity than 'cigalike' or 'drip-mod' devices. Smaller vapor cloud e-cigarettes and lower-price moist snuff were viewed as less dangerous, less buzz-inducing, and easier to use. Product ever users held stronger perceptions than never users about device type (e-cigarettes) and brands (moist snuff), while product naïve participants more strongly associated flavor with danger and buzz. CONCLUSIONS:Tobacco product characteristics convey product attributes to adolescents that may increase appeal. Restricting specific characteristics, including flavors, could reduce positive perceptions of these products among youth.
Project description:Objectives:The current study tests the substitutability of nicotine replacement therapy (NRT), electronic cigarettes (ECs), and very low nicotine cigarettes (VLNCs) in the context of an online experimental tobacco marketplace (ETM) that was designed to mimic the choices of smokers under 4 policy scenarios. Methods:Dutch cigarette smokers (N = 840) completed an online survey in July 2015. The ETM was comprised of conventional cigarettes, VLNCs, ECs (disposable/cartridge/tank systems), and NRT (lozenges/patches/tabs). All participants completed a scenario in which conventional cigarettes were banned. To test additional policy scenarios participants were randomized to one of 3 experiments: 1) no VLNCs, 2) all products available, or 3) no ECs. Hypothetical weekly purchases were made when the cost for conventional cigarettes was ½ market price (MP), MP, 2x MP, and 4x MP. Substitutability was measured by the change in estimated consumption as cigarette prices increased. Results:Tank and cartridge ECs and VLNCs were stronger cigarette substitutes than disposable ECs and NRT products. Substitution of ECs and NRT for cigarettes was dampened when VLNCs were available. Conclusions:The ETM offers a method to predict how smokers might respond to policies that alter the availability of potentially substitutable products available in the marketplace.
Project description:<h4>Importance</h4>Alkaline free-base nicotine is bitter and a respiratory irritant. High-nicotine electronic cigarette (e-cigarette) products contain acid additives that change nicotine from a free-base to a protonated salt chemical form, which could improve the sensory experience of vaping, particularly among never smokers unaccustomed to inhaling free-base nicotine.<h4>Objective</h4>To determine whether exposure to e-cigarettes with salt vs free-base nicotine formulations improves the appeal and sensory experience of vaping e-cigarettes and whether nicotine formulation effects differ by e-cigarette flavor and ever combustible cigarette smoking status.<h4>Design, setting, and participants</h4>Single-visit double-blind within-participant randomized clinical trial was conducted in an academic medical center outpatient clinical research facility in Southern California. Participants were 119 individuals with past 30-day e-cigarette or combustible cigarette use aged 21 years or older recruited from November 2019 to March 2020.<h4>Interventions</h4>Participants self-administered standardized puffs of each 10 differently flavored e-cigarette solutions using a pod-style device. Each flavor was administered in salt (benzoic acid added) and free-base (no benzoic acid) nicotine formulations with commensurate nicotine concentrations (mean, 23.6 mg/mL). The 20 solutions were administered in randomly assigned sequences. Immediately after puffing each solution, participants rated appeal and sensory attributes.<h4>Main outcomes and measures</h4>Self-reported appeal (mean of like, dislike [reverse-scored], and willingness to use again ratings) and 4 sensory attributes (sweetness, smoothness, bitterness, and harshness; analyzed individually) on visual analog scales with not at all and extremely anchors (range, 0-100).<h4>Results</h4>Of the 119 participants; 39 (32.8%) were female. The mean (SD) age was 42.1 (14.4) years; 105 (88.2%) were ever combustible cigarette smokers, and 66 (55.5%) were current e-cigarette users. Salt vs free-base nicotine formulations produced higher ratings of appeal (salt vs free-base mean difference effect estimate: b?=?12.0; 95% CI, 9.9-14.1; P?<?.001), sweetness (b?=?9.3; 95% CI, 7.1-11.4; P?<?.001), and smoothness (b?=?17.4; 95% CI, 15.2-19.6; P?<?.001) and lower ratings of bitterness (b?=?-13.3; 95% CI, -15.4 to -11.2; P?<?.001) and harshness (b?=?-21.0; 95% CI, -23.2 to -18.7; P?<?.001). Nicotine formulation effects largely generalized across different flavors and the smoothness-enhancing and harshness-reducing effects of nicotine salt were stronger in never vs ever cigarette smokers.<h4>Conclusions and relevance</h4>In this randomized clinical trial of adult current nicotine or tobacco product users, controlled exposure to e-cigarette puffs with salt vs free-base nicotine formulations appeared to increase product appeal and improve the sensory experience of vaping, particularly among never smokers. Regulatory policies limiting acid additives in e-cigarettes might reduce the appeal of high-nicotine e-cigarettes among populations deterred from vaping e-cigarettes that emit harsh aerosol.<h4>Trial registration</h4>ClinicalTrials.gov Identifier: NCT04399031.
Project description:In electronic cigarettes ("electronic nicotine delivery systems", ENDS), mixtures of propylene glycol (PG) and/or glycerol (GL; aka "vegetable glycerin", VG) with nicotine are vaporized to create a nicotine-containing aerosol. For a given composition, the temperature required to boil the liquid at 1 atmosphere must be at least somewhat greater than the boiling point (BP). The use of ENDS is increasing rapidly worldwide, yet the BP characteristics of the PG + GL system have been characterized as the mixtures; here we re-do this, but significantly, also study the effects of added water and nicotine. BP values at 1 atmosphere pressure were measured over the full binary composition range. Fits based on the Gibbs-Konovalov theorem provide BP as a function of composition (by mole-percent, by weight-percent, and by volume-percent). BPs of PG + GL mixtures were then tested in the presence of additives such as water (2.5 and 5 mol% added) and nicotine (3 mol%). Water was found to decrease the BP of PG + GL mixtures significantly at all compositions tested, and nicotine was found to decrease the BP of PG + GL mixtures containing ~75 GL: 25 PG (by moles) or more. The effect of added water (5, 10, and 15 mol% added) on electronic cigarette degradation production (some aldehydes and formaldehyde hemiacetals) was examined and found to have no significant impact on solvent (PG or GL) degradation for the particular device used.
Project description:Dangerous levels of harmful chemicals in electronic cigarette (e-cigarette) aerosols were reported by several studies, but variability in e-cigarette design and use patterns, and a rapid development of new devices, such as JUUL, hamper efforts to develop standardized testing protocols and understand health risks associated with e-cigarette use. In this study, we investigated the relative importance of e-cigarette design, power output, liquid composition, puff topography on e-cigarette emissions of carbonyl compounds, carbon monoxide (CO), and nicotine. Four popular e-cigarette devices representing the most common e-cigarette types (e.g., cig-a-like, top-coil, 'mod', and 'pod') were tested. Under the tested vaping conditions, a top-coil device generated the highest amounts of formaldehyde and CO. A 'pod' type device (i.e., JUUL) emitted the highest amounts of nicotine, while generating the lowest levels of carbonyl and CO as compared to other tested e-cigarettes. Emissions increased nearly linearly with puff duration, while puff flow had a relatively small effect. Flavored e-liquids generated more carbonyls and CO than unflavored liquids. Carbonyl concentrations and CO in e-cigarette aerosols were found to be well correlated. While e-cigarettes emitted generally less CO and carbonyls than conventional cigarettes, daily carbonyl exposures from e-cigarette use could still exceed acute exposure limits, with the top-coil device potentially posing more harm than conventional cigarettes.
Project description:Country-level differences in nicotine vaping products used and biomarkers of exposure among long-term e-cigarette users and dual users remain understudied. This cross-sectional study was conducted in 2014 in the United States (<i>n</i> = 166), United Kingdom (<i>n</i> = 129), and Poland (<i>n</i> = 161). We compared patterns of tobacco product use and nicotine and toxicant exposure among cigarette-only smokers (<i>n</i> = 127); e-cigarette-only users (<i>n</i> = 124); dual users of tobacco cigarettes and e-cigarettes (<i>n</i> = 95); and non-users (control group, <i>n</i> = 110) across three countries using mixed-effects linear regression. Compared with cigarette smokers, e-cigarette-only users had lower levels of toxicant biomarkers, but higher levels of nicotine biomarkers. Dual users had higher levels of toxicant biomarkers than e-cigarette-only users but similar levels to cigarette-only smokers. E-cigarette users in Poland, who overwhelmingly used refillable tank devices, exhibited greater levels of nicotine, and toxicant biomarkers relative to e-cigarette users in US/UK. Despite smoking fewer cigarettes, dual users from Poland exhibited similar levels of nicotine biomarkers compared with UK dual users, but higher than US dual users. Country-level differences in e-cigarette devices used and smoking behaviors (e.g., intensity) may contribute to differences in biomarker levels among users of the same products residing in different countries.
Project description:With the rapidly rising popularity and substantial evolution of electronic cigarettes (e-cigarettes) in the past 5-6 years, how these devices are used by vapers and consumers' exposure to aerosol emissions need to be understood. We used puffing topography to measure directly product use. We adapted a cigarette puffing topography device for use with e-cigarettes. We performed validation using air and e-cigarette aerosol under multiple regimes. Consumer puffing topography was measured for 60 vapers provided with rechargeable "cig-a-like" or larger button-activated e-cigarettes, to use ad-libitum in two sessions. Under all regimes, air puff volumes were within 1?mL of the target and aerosol volumes within 5?mL for all device types, serving to validate the device. Vapers' mean puff durations (2.0?s and 2.2?s) were similar with both types of e-cigarette, but mean puff volumes (52.2?mL and 83.0?mL) and mean inter-puff intervals (23.2?s and 29.3?s) differed significantly. The differing data show that product characteristics influence puffing topography and, therefore, the results obtained from a given e-cigarette might not read across to other products. Understanding the factors that affect puffing topography will be important for standardising testing protocols for e-cigarette emissions.