Effects of Electronic Cigarettes on Indoor Air Quality and Health.
ABSTRACT: With the rapid increase in electronic cigarette (e-cig) users worldwide, secondhand exposure to e-cig aerosols has become a serious public health concern. We summarize the evidence on the effects of e-cigs on indoor air quality, chemical compositions of mainstream and secondhand e-cig aerosols, and associated respiratory and cardiovascular effects. The use of e-cigs in indoor environments leads to high levels of fine and ultrafine particles similar to tobacco cigarettes (t-cigs). Concentrations of chemical compounds in e-cig aerosols are generally lower than those in t-cig smoke, but a substantial amount of vaporized propylene glycol, vegetable glycerin, nicotine, and toxic substances, such as aldehydes and heavy metals, has been reported. Exposures to mainstream e-cig aerosols have biologic effects but only limited evidence shows adverse respiratory and cardiovascular effects in humans. Long-term studies are needed to better understand the dosimetry and health effects of exposures to secondhand e-cig aerosols.
Project description:Electronic cigarettes (E-cigs) smoking or vaping is an emerging problem to public health due to its popularity. While its multi-faceted detrimental effects on human health are being reported, no current study addresses the effect of E-cigs on tumor metastasis, the main cause of tumor mortality. Using a well-established human breast cancer cell line MDA MB-231, we first showed that E-cig vapor extract (nicotine 24 mg/ml, propylene glycol 50%, vegetable glycerin 50%, no flavorings) significantly enhanced tumor cell migration (P<0.0001), but showed no significant effect on tumor cell proliferation (P>0.05). To evaluate the metastasis-promoting effect of E-cigs in vivo, we used NOD-SCID-Gamma mice and introduced tumor cells to the mice by tail vein injection. Among these mice, 4-week E-cigs exposure (nicotine 24 mg/ml, propylene glycol 50%, vegetable glycerin 50%, no flavorings, 2 h/day, 5 days/week) almost doubled the tumor load in the exposed lungs compared to controls (P=0.0036). While E-cig exposure did not alter the proliferative index of tumor cells colonized in the lungs (P=0.7953), tumor cell apoptosis was significantly reduced (P<0.001). Taken together, our data for the first time, demonstrated the lung colonization-promoting effects of E-cigs on human breast cancer cells. These findings show the risks of E-cigs on the lung metastasis of various cancers, and warrant more studies on the underlying mechanisms.
Project description:The use of electronic nicotine delivery systems (ENDS), also known as electronic-cigarettes (e-cigs), has raised serious public health concerns, especially in light of the 2019 outbreak of e-cig or vaping product use-associated acute lung injury (EVALI). While these cases have mostly been linked to ENDS that contain vitamin E acetate, there is limited research that has focused on the chronic pulmonary effects of the delivery vehicles (i.e., without nicotine and flavoring). Thus, we investigated lung function and immune responses in a mouse model following exposure to the nearly ubiquitous e-cig delivery vehicles, vegetable glycerin (VG) and propylene glycol (PG), used with a specific 70%/30% ratio, with or without vanilla flavoring. We hypothesized that mice exposed sub-acutely to these e-cig aerosols would exhibit lung inflammation and altered lung function. Adult female C57BL/6 mice (n = 11-12 per group) were exposed to filtered air, 70%/30% VG/PG, or 70%/30% VG/PG with a French vanilla flavoring for 2 h a day for 6 weeks. Prior to sacrifice, lung function was assessed. At sacrifice, broncho-alveolar lavage fluid and lung tissue were collected for lipid mediator analysis, flow cytometry, histopathology, and gene expression analyses. Exposures to VG/PG + vanilla e-cig aerosol increased lung tidal and minute volumes and tissue damping. Immunophenotyping of lung immune cells revealed an increased number of dendritic cells, CD4+ T cells, and CD19+ B cells in the VG/PG-exposed group compared to air, irrespective of the presence of vanilla flavoring. Quantification of bioactive lung lipids demonstrated a >3-fold increase of 2-arachidonoylglycerol (2-AG), an anti-inflammatory mediator, and a 2-fold increase of 12-hydroxyeicosatetraenoic acid (12-HETE), another inflammatory mediator, following VG/PG exposure, with or without vanilla flavoring. This suggests that e-cig aerosol vehicles may affect immunoregulatory molecules. We also found that the two e-cig aerosols dysregulated the expression of lung genes. Ingenuity Pathway Analysis revealed that the gene networks that are dysregulated by the VG/PG e-cig aerosol are associated with metabolism of cellular proteins and lipids. Overall, our findings demonstrate that VG and PG, the main constituents of e-liquid formulations, when aerosolized through an e-cig device, are not harmless to the lungs, since they disrupt immune homeostasis.
Project description:E-cigarette (e-cig) aerosols are complex mixtures of various chemicals including humectants (propylene glycol (PG) and vegetable glycerin (VG)), nicotine, and various flavoring additives. Emerging research is beginning to challenge the "relatively safe" perception of e-cigarettes. Recent studies suggest e-cig aerosols provoke oxidative stress; however, details of the underlying molecular mechanisms remain unclear. Here we used a redox proteomics assay of thiol total oxidation to identify signatures of site-specific protein thiol modifications in Sprague-Dawley rat lungs following in vivo e-cig aerosol exposures. Histologic evaluation of rat lungs exposed acutely to e-cig aerosols revealed mild perturbations in lung structure. Bronchoalveolar lavage (BAL) fluid analysis demonstrated no significant change in cell count or differential. Conversely, total lung glutathione decreased significantly in rats exposed to e-cig aerosol compared to air controls. Redox proteomics quantified the levels of total oxidation for 6682 cysteine sites representing 2865 proteins. Protein thiol oxidation and alterations by e-cig exposure induced perturbations of protein quality control, inflammatory responses and redox homeostasis. Perturbations of protein quality control were confirmed with semi-quantification of total lung polyubiquitination and 20S proteasome activity. Our study highlights the importance of redox control in the pulmonary response to e-cig exposure and the utility of thiol-based redox proteomics as a tool for elucidating the molecular mechanisms underlying this response.
Project description:With the rapid growth of the electronic cigarette (e-cig) market, there is an increasing number of vape shops that exclusively sell e-cigs. The use of e-cigs in the vape shop is a primary source of indoor particles, which might transport to its nearby indoor spaces in the multiunit setting. In this study, six pairs of vape shops and neighboring businesses in Southern California were recruited for real-time measurements of particulate pollutants between February 2017 and October 2019. The mean (SD) particle number concentration (PNC) and PM<sub>2.5</sub> concentration in the studied vape shops were 2.8 × 10<sup>4</sup> (2.3 × 10<sup>4</sup>) particles/cm<sup>3</sup> and 276 (546) ?g/m<sup>3</sup>, which were substantially higher than those in neighboring businesses and outdoor areas. In addition, 24-h time-weighted average (TWA) nicotine sampling was conducted in the six pairs and three additional pairs. Nicotine was detected in the air of all the studied vape shops and neighboring businesses, in which the mean (SD) concentration was 2.59 (1.02) and 0.17 (0.13) ?g/m<sup>3</sup>, respectively. Inside vape shops, the dilution-corrected vaping density (puffs/h/100 m<sup>3</sup>) is a strong predictor of the particle concentration, and nicotine concentration highly depends on the air exchange rate (AER). Out of the six studied pairs, PNCs in five vape shops and PM<sub>2.5</sub> in two vape shops were significantly correlated with those in their neighboring businesses. This correlation was stronger when the door of the vape shop was closed. When the door was open, environmental electronic vaping (EEV) aerosols, especially smaller particles, could transport from the vape shop to the outdoor environment. Overall, e-cig usage in the vape shop impacts both its own and nearby air quality, raising concerns regarding the risk of exposure to EEV aerosols in the surrounding environments.
Project description:An electronic cigarette (e-cig) generates aerosols by vaporizing the e-liquid, which mainly consists of propylene glycol (PG), vegetable glycerin (VG), and nicotine. Understanding the effects of e-liquid main compositions on e-cig aerosols is important for exposure assessment. This study investigated how the PG/VG ratio and nicotine content affect e-cig aerosol emissions and dynamics. A tank-based e-cig device with 10 different flavorless e-liquid mixtures (e.g., PG/VG ratios of 0/100, 10/90, 30/70, 50/50, and 100/0 with 0.0% or 2.4% nicotine) was used to puff aerosols into a 0.46 m3 stainless steel chamber for 0.5 h. Real-time measurements of particle number concentration (PNC), fine particulate matter (PM2.5), and particle size distributions were conducted continuously throughout the puffing and the following 2-h decay period. During the decay period, particle loss rates were determined by a first-order log-linear regression and used to calculate the emission factor. The addition of nicotine in the e-liquid significantly decreased the particle number emission factor by 33%. The PM2.5 emission factor significantly decreased with greater PG content in the e-liquid. For nicotine-free e-liquids, increasing the PG/VG ratio resulted in increased particle loss rates measured by PNC and PM2.5. This pattern was not observed with nicotine in the e-liquids. The particle loss rates, however, were significantly different with and without nicotine especially when the PG/VG ratios were greater than 30/70. Compared with nonvolatile diethyl-hexyl subacute (DEHS) aerosols, e-cig particle concentration decayed faster inside the chamber, presumably due to evaporation. These results have potential implications for assessing human exposure to e-cig aerosols.
Project description:Oxidants or nanoparticles have recently been identified as constituents of aerosols released from various styles of electronic cigarettes (E-cigs). Cells in the lung may be directly exposed to these constituents and harbor reactive properties capable of incurring acute cell injury. Our results show mitochondria are sensitive to both E-cig aerosols and aerosol containing copper nanoparticles when exposed to human lung fibroblasts (HFL-1) using an Air-Liquid Interface culture system, evident by elevated levels of mitochondrial ROS (mtROS). Increased mtROS after aerosol exposure is associated with reduced stability of OxPhos electron transport chain (ETC) complex IV subunit and nuclear DNA fragmentation. Increased levels of IL-8 and IL-6 in HFL-1 conditioned media were also observed. These findings reveal both mitochondrial, genotoxic, and inflammatory stresses are features of direct cell exposure to E-cig aerosols which are ensued by inflammatory duress, raising a concern on deleterious effect of vaping.
Project description:<h4>Background</h4>Nicotine-containing electronic cigarette (e-cig) use has become widespread. However, understanding the biological impact of e-cigs compared with smoking on the lung is needed. There are major gaps in knowledge for chronic effects and for an etiology to recent acute lung toxicity leading to death among vapers.<h4>Methods</h4>We conducted bronchoscopies in a cross-sectional study of 73 subjects (42 never-smokers, 15 e-cig users, and 16 smokers). Using bronchoalveolar lavage and brushings, we examined lung inflammation by cell counts, cytokines, genome-wide gene expression, and DNA methylation.<h4>Results</h4>There were statistically significant differences among never-smokers, e-cig users, and smokers for inflammatory cell counts and cytokines (FDR <i>q</i> < 0.1). The e-cig users had values intermediate between smokers and never-smokers, with levels for most of the biomarkers more similar to never-smokers. For differential gene expression and DNA methylation, e-cig users also more like never-smokers; many of these genes corresponded to smoking-related pathways, including those for xenobiotic metabolism, aryl hydrocarbon receptor signaling, and oxidative stress. Differentially methylated genes were correlated with changes in gene expression, providing evidence for biological effects of the methylation associations.<h4>Conclusions</h4>These data indicate that e-cigs are associated with less toxicity than cigarettes for smoking-related pathways. What is unknown may be unique effects for e-cigs not measured herein, and a comparison of smokers completely switching to e-cigs compared with former smokers. Clinical trials for smokers switching to e-cigs who undergo serial bronchoscopy and larger cross-sectional studies of former smokers with and without e-cig use, and for e-cigs who relapse back to smoking, are needed.<h4>Impact</h4>These data can be used for product regulation and for informing tobacco users considering or using e-cigs. What is unknown may be unique effects for e-cigs not measured herein, and clinical trials with serial bronchoscopy underway can demonstrate a direct relationship for changes in lung biomarkers.
Project description:BACKGROUND:Electronic cigarettes (e-cigs) are an increasingly popular alternative to smoking, helping to prevent relapse in those trying to quit and with the potential to reduce harm as they are likely to be safer than standard cigarettes. Many women return to smoking in the postpartum period having stopped during pregnancy, and while this can affect their decisions about breastfeeding, little is known about women's opinions on using e-cigs during this period. OBJECTIVE:The aim of this study is to explore online forum users' current attitudes, motivations, and barriers to postpartum e-cig use, particularly as a breastfeeding mother. METHODS:Data were collected via publicly accessible (identified by Google search) online forum discussions, and a priori codes identified. All transcripts were entered into NVivo for analysis, with a template approach to thematic analysis being used to code all transcripts from which themes were derived. RESULTS:Four themes were identified: use, perceived risk, social support and evidence, with a number of subthemes identified within these. Women were using e-cigs to prevent postpartum return to smoking, but opinions on their safety were conflicting. They were concerned about possible transfer of harmful products from e-cigs via breastmilk and secondhand exposure, so they were actively seeking and sharing information on e-cigs from a variety of sources. Although some women were supportive of e-cig use, others provided harsh judgement for mothers who used them. CONCLUSIONS:E-cigs have the potential to reduce the number of women who return to smoking in the postpartum period and potentially improve breastfeeding rates, if breastfeeding mothers have access to relevant and reliable information. Health care providers should consider discussing e-cigs with mothers at risk of returning to smoking in the postpartum period.
Project description:BACKGROUND:The United States Food and Drug Administration has prioritized understanding the dependence potential of electronic cigarettes (e-cigs). Dependence is often estimated in part by examining frequency of use; however measures of e-cig use are not well developed because of varying product types. This study used an e-cig automatic puff counter to evaluate the value of self-reported e-cig use measures in predicting actual use (puffs). METHODS:Data were collected from a two-site randomized placebo-controlled trial evaluating the effects of e-cigs on toxicant exposure in smokers attempting to reduce their cigarette consumption. Participants randomized to an e-cig condition self-reported their e-cig frequency of use (times per day-one "time" consists of around 15 puffs or lasts around 10 minutes) on the Penn State Electronic Cigarette Dependence Index (PSECDI) and kept daily diary records of the number of puffs per day from the e-cig automatic puff counter. A linear mixed-effects model was used to determine the predictive value of the times per day measure. Correlations were used to further investigate the relationship. RESULTS:A total of 259 participants with 1165 observations of e-cig use were analyzed. Self-reported e-cig use in times per day was a significant predictor of e-cig puffs per day (p < .01). The Spearman correlation between measures was r equal to .58. Examination of individual participant responses revealed some potential difficulties reporting and interpreting times per day because of the difference in use patterns between cigarettes and e-cigs. CONCLUSION:This study provides evidence that the self-reported PSECDI measure of times per day is a significant predictor of actual frequency of e-cig puffs taken. IMPLICATIONS:Self-reported measures of e-cig frequency of use are predictive of actual use, but quantifying e-cig use in patterns similar to cigarettes is problematic.
Project description:Electronic cigarettes (e-cigs) have increased in popularity over the last few years, especially with youth and young adults. However, little is known about the health effects of using these devices. Additionally, relatively few studies have explored college students' e-cig use and perceptions of safety. In this study, perceptions of e-cig safety were compared among three groups of college students-those who had never tried, had tried, and currently use e-cigs. Study findings suggest interesting differences between the three groups, with participants who had tried as well as those who currently use e-cigs having more positive views of the devices. For example, current users were more likely to view e-cigs as safe and healthy choices and less likely to view them as tobacco products. Further, compared to participants who had not tried e-cigs, individuals who had tried or currently use e-cigs were more likely to believe that vapor was safe to others (i.e., no second- or third-hand effects). Understanding the perceptions and use of e-cigs among college students is important in order to develop communication strategies for anti-tobacco campaigns that effectively relate safety concerns to these audiences.