Search

RNA-seq is a high-throughput sequencing technology widely used for gene transcript discovery and quantification under different biological or biomedical conditions. A fundamental research question in most RNA-seq experiments is the identification of differentially expressed genes among experimental conditions or sample groups. Numerous statistical methods for RNA-seq differential analysis have been proposed since the emergence of the RNA-seq assay. To evaluate popular differential analysis methods used in the open source R and Bioconductor packages, we conducted multiple simulation studies to compare the performance of eight RNA-seq differential analysis methods used in RNA-seq data analysis (edgeR, DESeq, DESeq2, baySeq, EBSeq, NOISeq, SAMSeq, Voom). The comparisons were across different scenarios with either equal or unequal library sizes, different distribution assumptions and sample sizes. We measured performance using false discovery rate (FDR) control, power, and stability. No significant differences were observed for FDR control, power, or stability across methods, whether with equal or unequal library sizes. For RNA-seq count data with negative binomial distribution, when sample size is 3 in each group, EBSeq performed better than the other methods as indicated by FDR control, power, and stability. When sample sizes increase to 6 or 12 in each group, DESeq2 performed slightly better than other methods. All methods have improved performance when sample size increases to 12 in each group except DESeq. For RNA-seq count data with log-normal distribution, both DESeq and DESeq2 methods performed better than other methods in terms of FDR control, power, and stability across all sample sizes. Real RNA-seq experimental data were also used to compare the total number of discoveries and stability of discoveries for each method. For RNA-seq data analysis, the EBSeq method is recommended for studies with sample size as small as 3 in each group, and the DESeq2 method is recommended for sample size of 6 or higher in each group when the data follow the negative binomial distribution. Both DESeq and DESeq2 methods are recommended when the data follow the log-normal distribution. more...

BackgroundMore smokers report using e-cigarettes to help them quit than FDA-approved pharmacotherapy.ObjectiveTo assess the association of e-cigarettes with future abstinence from cigarette and tobacco use.DesignCohort study of US sample, with annual follow-up.ParticipantsUS adult (ages 18+) daily cigarette smokers identified at Wave 1 (W1; 2013-14) of the PATH Study, who reported a quit attempt before W2 and completed W3 (n = 2443).ExposuresUse of e-cigarettes, pharmacotherapy (including nicotine replacement therapy), or no product for last quit attempt (LQA), and current daily e-cigarette use at W2.AnalysisPropensity score matching (PSM) of groups using different methods to quit.Outcome measures12+ months abstinence at W3 from cigarettes and from all tobacco (including e-cigarettes). 30+ days abstinence at W3 was a secondary outcome.ResultsAmong daily smokers with an LQA, 23.5% used e-cigarettes, 19.3% used pharmacotherapy only (including NRT) and 57.2% used no product. Cigarette abstinence for 12+ months at W3 was ~10% in each group. Half of the cigarette abstainers in the e-cigarette group were using e-cigarettes at W3. Different methods to help quitting had statistically comparable 12+ month cigarette abstinence at W3 (e-cigarettes vs no product: Risk Difference (RD) = 0.01, 95% CI: -0.04 to 0.06; e-cigarettes vs pharmacotherapy: RD = 0.02, 95% CI:-0.04 to 0.09). Likewise, daily e-cigarette users at W2 did not show a cessation benefit over comparable no-e-cigarette users and this finding was robust to sensitivity analyses. Abstinence for 30+ days at W3 was also similar across products.LimitationsThe frequency of e-cigarette use during the LQA was not assessed, nor was it possible to assess continuous abstinence from the LQA.ConclusionAmong US daily smokers who quit cigarettes in 2014-15, use of e-cigarettes in that attempt compared to approved cessation aids or no products showed similar abstinence rates 1-2 years later. more...

INTRODUCTION:Flavored e-cigarettes are enticing to new users and established cigarette smokers using e-cigarettes to quit smoking due to the wide variety of flavor options. However, specific flavor combinations that are popular among e-cigarette users are understudied. Recently, the Deeming rule extended the US Food and Drug Administration's authority over all tobacco products, including e-cigarettes. METHODS:The Population Assessment of Tobacco and Health Study Wave 2 data were analyzed to assess the prevalence of self-reported flavor categories that are used individually and in combination with other flavor categories among past 30-day youth and adult e-cigarette users in the US. RESULTS:Most youth and adult participants reported using a flavored e-cigarette. Reporting an individual flavor category was more common than reporting a combination of flavor categories. Fruit flavor was the most common flavor category reported among youth, and 'menthol/mint' was most common among adults. Fruit and candy/other sweets were the most common flavor categories reported together among both youth and adult past 30-day e-cigarette users. CONCLUSIONS:The use of flavored e-cigarettes is very popular among youth and adults. Most consumers reported using a single flavor category, although some consumers did use a combination of flavor categories. Preference for menthol/mint among adults may represent a carryover from associations with tobacco cigarettes. Typically, sweeter flavors, such as fruit, were among the most popular flavor categories reported, both individually and in combination with other flavors, while more bitter flavors (i.e.: clove/spice) were less common. IMPLICATIONS:This study identified predominant flavor categories among past 30-day youth and adult e-cigarette users. Findings indicate that the wide variety of flavors available and the freedom to "mix-and-match" flavors may maintain use of e-cigarettes among youth and adults, and future research should focus on the composition of the ENDS liquid/vapor to disentangle the contributions of sweeteners and flavorants. more...

Abstract Rationale While tobacco industry data suggests that switching from combustible cigarettes to heated tobacco products (HTPs), like IQOS, may reduce the users’ exposure to respiratory toxicants, it is not known if using HTPs impacts the outcomes of acute respiratory infections. Objectives Does switching from cigarettes to HTPs improve responses to pulmonary infection. Methods We conducted experiments in which 3 groups of mice were pre-exposed to cigarette smoke for 8 weeks, followed by 8-week exposure to (1) HTPs (tobacco product switching), (2) air (smoking cessation), or (3) continued exposure to cigarette smoke. Pulmonary bacterial clearance and surrogate markers of lung damage were assessed as study outcomes. Main results Significantly compromised clearance of bacteria from the lungs post-acute challenge occurred in both the switching group and in mice continuously exposed to cigarette smoke. Bacterial clearance, inflammatory T-cell infiltration into the lungs, and albumin leak improved at 12 h post-acute challenge in the switching group compared to mice continuously exposed to cigarette smoke. Bacterial clearance, total lung immune-cell infiltration, inflammatory T-cell infiltration into the lungs, the content of total proteins in the BAL, and albumin leak measured post-acute challenge were compromised in the switching group compared to mice in the cessation group. Switching from cigarettes to HTPs did not improve lung myeloperoxidase and neutrophil elastase levels (markers for lung inflammation and damage), which, however, were significantly reduced in the cessation group. Conclusions This study reveals only a modest improvement in respiratory infection outcomes after switching exposure from cigarettes to HTPs and significantly compromised outcomes compared to a complete cessation of exposure to all tobacco products. more...

Abstract Nicotine vaping products (NVPs) and heated tobacco products (HTPs) are designed to replicate the sensory and behavioural aspects of smoking cigarettes while avoiding combustion. The success of these products as harm reduction tools will partially depend on their ability to satisfy smokers and alleviate nicotine-related withdrawal symptoms. This study aims to compare short-term effects of NVPs (Juul and Aspire PockeX) versus HTPs (IQOS) on smoking-related withdrawal relief, product satisfaction, intention to switch to NVP/HTP, perceptions and attitudes in UK adult cigarette smokers naïve to these products. In a randomized cross-over study, 45 participants visited the lab twice, at each visit trying one of the two products (NVP/HTP) and completing a questionnaire. Responses were normalized on a 0–100% scale and mean differences (MD) between NVP and HTP scores computed, with positive and negative MD values indicating greater endorsement for NVP and HTP, respectively. Cigarette cravings were reduced similarly (~ 20.0%) by both products (MD = 4.5%, 95%Confidence Interval (CI) − 4.8, 13.8). Direct positive effects (MD = − 3.5%, 95%CI − 7.2, 0.2) and adverse side effects (MD = 1.8%, 95%CI − 0.3, 3.8) were comparable after each product use, though marginally favouring HTPs. HTPs were perceived as more satisfying overall (MD = − 13.2%, 95%CI − 20.3 − 6.1) than NVPs but both were perceived as similarly addictive (MD = 3.6%, 95%CI − 4.6, 11.8), relative to cigarettes. Intention to switch to either product was comparable (MD = 4.0%, 95%CI − 5.7, 13.8). Comparison of acute use of NVP versus HTP in a sample of UK smokers naïve to these products suggests that HTPs are perceived as more satisfying than NVPs, though still less satisfying than cigarettes. Registration: The analysis plan was pre-registered, and it is available at https://osf.io/6ymdu more...

Abstract Rationale Due to the relatively short existence of alternative tobacco products, gaps exist in our current understanding of their long-term respiratory health effects. We therefore undertook the first-ever side-by-side comparison of the impact of chronic inhalation of aerosols emitted from electronic cigarettes (EC) and heated tobacco products (HTP), and combustible cigarettes (CC) smoke. Objectives To evaluate the potential differential effects of alternative tobacco products on lung inflammatory responses and efficacy of vaccination in comparison to CC. Methods Mice were exposed to emissions from EC, HTP, CC, or air for 8 weeks. BAL and lung tissue were analyzed for markers of inflammation, lung damage, and oxidative stress. Another group was exposed for 12 weeks and vaccinated and challenged with a bacterial respiratory infection. Antibody titers in BAL and sera and pulmonary bacterial clearance were assessed. Main results EC- and HTP-aerosols significantly augmented lung immune cell infiltrates equivalent to that achieved following CC-exposure. HTP and CC significantly increased neutrophil numbers compared to EC. All products augmented numbers of B cells, T cells, and pro-inflammatory IL17A+ T cells in the lungs. Decreased lung antioxidant activity and lung epithelial and endothelial damage was induced by all products. EC and HTP differentially augmented inflammatory cytokines/chemokines in the BAL. Generation of immunity following vaccination was impaired by EC and HTP but to a lesser extent than CC, with a CC > HTP > EC hierarchy of suppression of pulmonary bacterial clearance. Conclusions HTP and EC-aerosols induced a proinflammatory pulmonary microenvironment, lung damage, and suppressed efficacy of vaccination. more...

E-liquids contain combinations of chemicals, with many enhancing the sensory attractiveness of the product. Studies are needed to understand and characterize e-liquid ingredients, particularly flavorings, to inform future research and regulations of these products. We identified common flavor ingredients in a convenience sample of commercial e-liquids using gas chromatography–mass spectrometry. E-liquid flavors were categorized by flavor descriptors provided on the product packaging. A Flavor Ingredient Wheel was developed to link e-liquid flavor ingredients with flavor categories. An analysis of 109 samples identified 48 flavor ingredients. Consistency between the labeled flavor and ingredients used to produce such flavor was found. Our novel Flavor Ingredient Wheel organizes e-liquids by flavor and ingredients, enabling efficient analysis of the link between ingredients and their flavor profiles and allowing for quick assessment of an e-liquid ingredient’s flavor profile. Investigating ingredient profiles and identifying and classifying commonly used chemicals in e-liquids may assist with future studies and improve the ability to regulate these products. more...

Heated Tobacco Products (HTPs) purport to reduce exposure to tobacco-related toxicants compared to combustible cigarettes. This cross-sectional study examined the content of nicotine, two humectants (propylene glycol (PG) and vegetable glycerin (VG)), and four tobacco-specific nitrosamines (TSNAs: NNN, NNK, NAT, and NAB) in the tobacco filler of a popular HTP brand (IQOS). Non-menthol and menthol IQOS sticks were purchased from nine countries between 2017 and 2020 and were classified into two versions (“Bold” and “Light”) using Philip Morris’s flavor descriptors. The average nicotine concentration was 4.7 ± 0.5 mg/stick, and the highest nicotine concentration was found in products from Japan (5.1 ± 0.2 mg/stick). VG was the dominant humectant found in all sticks, with an average concentration of (31.5 ± 2.3 mg/stick). NNN, NNK, and NAT were substantially higher in the “Bold” sticks than the “Light” sticks. Significant differences between countries for TSNAs were also observed: the NAT and NAB contents were the highest in the “Light” products from Canada (192.5 ± 24.1 and 22.9 ± 1.0 ng/stick, respectively); the NNK concentration was the highest in the “Bold” products from Poland (64.8 ± 7.9 ng/stick); and the highest NNN concentrations were observed in the “Bold” products from South Africa (488.9 ± 26.7 ng/stick). As NNN and NNK are known human carcinogens, and as humectants like PG and VG can degrade into toxic carbonyl compounds upon heating, monitoring the concentration of these chemicals in HTPs is important for protecting users’ health and ensuring compliance with regulations. more...

The health benefits of switching from tobacco to electronic cigarettes (ECs) are neither confirmed nor well characterized. To address this problem, we used RNA-seq analysis to compare the nasal epithelium transcriptome from the following groups (n = 3 for each group): (1) former smokers who completely switched to second generation ECs for at least 6 months, (2) current tobacco cigarette smokers (CS), and (3) non-smokers (NS). Group three included one former cigarette smoker. The nasal epithelial biopsies from the EC users vs. NS had a higher number of differentially expressed genes (DEGs) than biopsies from the CS vs. NS and CS vs. EC sets (1817 DEGs total for the EC vs. NS, 407 DEGs for the CS vs. NS, and 116 DEGs for the CS vs. EC comparison). In the EC vs. NS comparison, enriched gene ontology terms for the downregulated DEGs included cilium assembly and organization, whereas gene ontologies for upregulated DEGs included immune response, keratinization, and NADPH oxidase. Similarly, ontologies for cilium movement were enriched in the downregulated DEGs for the CS vs. NS group. Reactome pathway analysis gave similar results and also identified keratinization and cornified envelope in the upregulated DEGs in the EC vs. NS comparison. In the CS vs. NS comparison, the enriched Reactome pathways for upregulated DEGs included biological oxidations and several metabolic processes. Regulator effects identified for the EC vs. NS comparison were inflammatory response, cell movement of phagocytes and degranulation of phagocytes. Disease Ontology Sematic Enrichment analysis identified lung disease, mouth disease, periodontal disease and pulmonary fibrosis in the EC vs. NS comparison. Squamous metaplasia associated markers, keratin 10, keratin 13 and involucrin, were increased in the EC vs. NS comparison. Our transcriptomic analysis showed that gene expression profiles associated with EC use are not equivalent to those from non-smokers. EC use may interfere with airway epithelium recovery by promoting increased oxidative stress, inhibition of ciliogenesis, and maintaining an inflammatory response. These transcriptomic alterations may contribute to the progression of diseases with chronic EC use. more...

Following their introduction a decade ago, electronic cigarettes (e-cigarettes) have grown in popularity. Given their novelty, knowledge of the health consequences of e-cigarette use remains limited. Epidemiologic studies have not comprehensively explored associations between e-cigarette use and hypertension, a highly prevalent health condition and major contributor to cardiovascular disease burden. In this study, cross-sectional associations of cigarette smoking and e-cigarette use (vaping) with self-reported diagnosed hypertension were evaluated among 19,147 18–55 year old respondents in Wave 3 (2015–2016) of the Population Assessment of Tobacco and Health Study. Multivariable analyses first modeled smoking and vaping as separate 2-category variables, then as a 6-category composite variable accounting for former smoking. After adjusting for potential confounders, current vaping (aOR = 1.31; 95%CI: 1.05–1.63) and current smoking (aOR = 1.27; 95%CI: 1.10–1.47) were both associated with higher odds of hypertension. In analyses modeling smoking and vaping compositely, respondents who were concurrently smoking and vaping had the highest odds of hypertension (aOR = 1.77; 95%CI: 1.32–2.39 [referent: never smokers]). These results differ somewhat from prior epidemiologic studies of vaping and respiratory outcomes, which consistently report smaller point estimates for current vaping than for current smoking. Our findings reinforce the uncertainty surrounding long-term health consequences of vaping, as well as highlight important distinctions between respiratory and cardiovascular outcomes when considering the harm reduction potential of e-cigarettes. more...

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 (n = 166), United Kingdom (n = 129), and Poland (n = 161). We compared patterns of tobacco product use and nicotine and toxicant exposure among cigarette-only smokers (n = 127); e-cigarette-only users (n = 124); dual users of tobacco cigarettes and e-cigarettes (n = 95); and non-users (control group, n = 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. more...

Summary: Background: Substitution of noncombustible tobacco products for cigarettes could improve respiratory symptoms. We hypothesized that complete cigarette-to-e-cigarette switching would improve respiratory symptoms compared to continued smoking. Methods: Longitudinal analysis of data from waves 2–6 (W2–W6; 2014–2021) of the Population Assessment of Tobacco and Health (PATH) Study, an observational cohort study that surveyed 5653 US adults ≥18 years without COPD/chronic bronchitis/emphysema. We compiled 14,947 two-wave (1–2 year) observations with persons who smoked cigarettes at baseline and compared the relation between functionally important respiratory symptoms and switching to exclusive e-cigarette use or quitting tobacco versus continued cigarette use (reference). A 9-point wheezing/nighttime cough index was dichotomized based on index scores of ≥2 or ≥3, previously associated with poorer functional health. Multivariable models assessed how changes in cigarette use predicted worsening/improvement of symptoms. Findings: Among those with an index score more...

Background/Objectives: Electronic cigarettes (e-cigarettes) are commonly used by former smokers as an alternative product to conventional cigarettes and also by young adults and adolescents to deliver nicotine. E-cigarettes are thought to be a less harmful and more socially acceptable alternative to tobacco smoking; however, their long-term effects on health, including oral health, are currently unknown. Methods: A literature search for relevant papers indexed in the literature from 2016 to 2023 was conducted using the PubMed, Scopus, and Google Scholar databases. In our paper, we included clinical trials and both in vivo and in vitro research concerning the impact of e-cigarettes on oral health. Results: E-cigarettes impact the oral cavity, which is directly exposed to inhaled chemicals present in e-cigarette aerosols. The use of e-cigarettes has been linked to teeth discoloration and dental caries, promoting the development of periodontal diseases and causing oral mucosa lesions, including oral cancer. E-cigarette aerosols might also negatively affect the oral microbiome by suppressing the growth of commensal bacteria and increasing the population of bacteria responsible for developing numerous oral disorders. E-cigarettes also impact saliva composition and its properties, including reducing saliva’s antibacterial and antioxidant properties, which may subsequently lead to the promotion of oral diseases. Conclusions: The outcomes suggest that e-cigarette usage may cause the development of oral diseases, however further longitudinal studies of a larger and homogenous group of e-cigarette users are required. more...

Abstract Background Electronic cigarettes (e-cigarettes) are relatively new tobacco products that are attracting public attention due to their unique features, especially their many flavor options and their potential as an alternative to cigarettes. However, uncertainties remain regarding the determinants and consequences of e-cigarette use because current research on e-cigarettes is made more difficult due to the lack of psychometrically sound instruments that measure e-cigarette related constructs. This systematic review therefore seeks to identify the instruments in the field that are designed to assess various aspects of e-cigarette use or its related constructs and analyze the evidence presented regarding the psychometric properties of the identified instruments. Methods This systematic review utilized six search engines: PubMed, Medline, CINAHL, PsycINFO, Web of Science, and EMBASE, to identify articles published in the peer-reviewed journals from inception to February 2022 that contained development or validation processes for these instruments. Results Eighteen articles describing the development or validation of 22 unique instruments were identified. Beliefs, perceptions, motives, e-cigarette use, and dependence, were the most commonly assessed e-cigarette related constructs. The included studies reported either construct or criterion validity, with 14 studies reporting both. Most studies did not report the content validity; for reliability, most reported internal consistencies using Cronbach’s alpha, with 15 instruments reporting Cronbach’s alpha > 0.70 for the scale or its subscales. Conclusions Twenty-two instruments with a reported development or validation process to measure e-cigarette related constructs are currently available for practitioners and researchers. This review provides a guide for practitioners and researchers seeking to identify the most appropriate existing instruments on e-cigarette use based on the constructs examined, target population, psychometric properties, and instrument length. The gaps identified in the existing e-cigarette related instruments indicate that future studies should seek to extend the validity of the instruments for diverse populations, including adolescents. Instruments that explore additional aspects of e-cigarette use and e-cigarette related constructs to help build a strong theoretical background and expand our current understanding of e-cigarette use and its related constructs, should also be developed. more...

This perspective summarizes available evidence on biomarkers of exposure in electronic nicotine delivery system (ENDS) users to aid the overall assessment of the health consequences of using ENDS. Identification of novel biomarkers of exposure specific to ENDS use remains challenging because chemicals emitted from ENDS devices have many familiar sources. The biomarker levels of many tobacco-related toxicants measured in biological samples collected from ENDS users did not differ significantly from non-users, except for nicotine metabolites and a small number of biomarkers of exposure to volatile organic compounds and tobacco-specific tobacco nitrosamines. Several studies have shown that while exposed to nicotine, long-term exclusive ENDS users showed significantly lower levels of toxicant biomarkers than cigarette smokers. Studies have also shown that concurrent users of ENDS and combustible cigarettes (‘dual users’) are not reducing overall exposure to harmful toxicants compared to exclusive cigarette smokers. Because of an absence of validated ENDS-specific biomarkers, we recommend combining several biomarkers to differentiate tobacco product user groups in population-based studies and monitor ENDS compliance in randomized controlled trials. Using a panel of biomarkers would provide a better understanding of health effects related to ENDS use. more...

Introduction: Novel tobacco-free oral nicotine products are not combusted, easy to conceal, available in flavors, and do not contain tobacco leaf. Since 2016, oral nicotine product sales have increased and may be gaining popularity among youth. This study aims to examine the trends in the prevalence and correlates of oral nicotine product use among U.S. youth. Methods: Data from participants aged 16–19 years in the U.S. International Tobacco Control Policy Evaluation Project Youth Tobacco and Vaping Survey were analyzed cross-sectionally from August 2019, February 2020, August 2020, February 2021, and August 2021. Weighted descriptive statistics and logistic regressions were used to describe the use and correlates of oral nicotine products. Results: Oral nicotine product use significantly increased from 3.5% in August 2019 to 4.1% in August 2021. Oral nicotine product use was most prevalent among those aged 18 years, male, and non-Hispanic White. Those who used cigarettes (AOR=2.18, 95% CI=19.37, 40.88), nicotine vaping products (AOR=4.27, 95% CI=3.02, 6.04), and smokeless tobacco (AOR=28.14, 95% CI=19.37, 40.88) in the past 30 days were more likely to report recent use of oral nicotine products. Conclusions: Although oral nicotine products are less popular among U.S. youth than cigarettes, nicotine vaping products, and smokeless tobacco, their prevalence of use significantly increased. Oral nicotine product users are more likely to use other nicotine products, but the availability of flavors and easy-to-conceal design may be appealing to those who may not use nicotine products. Researchers should continue to observe the behaviors associated with oral nicotine product use to inform the need for future regulatory efforts. more...

Introduction Flavors other than tobacco flavor have been identified as a major reason for electronic nicotine delivery system (ENDS) initiation in youth and are thought to contribute to the continued use of ENDS in users of all ages. Our previous research showed a significant association between overall ENDS use and COPD. This study aims to identify the association of ENDS flavor categories with self-reported COPD. Methods The data analysis included 4909 adults from Population Assessment of Tobacco and Health (PATH) Wave 4 data who were ever established ENDS users and responded to an item about diagnosis of COPD. Weighted multivariable logistic regression models were used to examine the association between different ENDS flavors and self-reported COPD considering complex sampling design. Results Among 4909 ever established ENDS users, 418 adults (weighted percentage 9.8%) had self-reported COPD. Self-reported COPD prevalence differed between different ENDS flavor categories, with the highest (weighted percentage 19.9%) occurring among tobacco flavor users. Compared to non-tobacco flavor categories, tobacco flavor category showed significantly higher association with self-reported COPD (AOR=2.05; 95% CI: 1.20–3.53), after adjusting for potential confounding variables. No significant associations with self-reported COPD were found for other examined ENDS flavor categories including menthol/mint, fruit, candy/ desserts/other-sweets, and other flavors, compared to their corresponding non-users. Conclusions Tobacco flavored ENDS use was significantly associated with self-reported COPD. Future studies are needed to confirm the biological and epidemiological association of flavored ENDS use with COPD. more...

Introduction Tobacco companies have introduced heated tobacco products (HTPs), such as IQOS, which may compete with e-cigarettes among smokers interested in switching to potentially reduced-risk products. Non-smokers may also start using IQOS if they believe this product is less harmful than other nicotine products. Smokers’ and non-smokers’ decisions may be driven by relative harm perceptions of emerging nicotine products. We aimed to examine relative harm perceptions between IQOS, e-cigarettes, and cigarettes, among nicotine product users and non-users. Material and Methods We conducted a web survey with Canadian respondents (aged ≥20 years; n=268) in September–October 2018. Perceptions about relative harm between IQOS (available for sale since 2017 and subject to the same comprehensive marketing restrictions as cigarettes in Canada), e-cigarettes, and cigarettes, were assessed among non-users (n=79), exclusive smokers (n=78), exclusive e-cigarette users (n=32), and dual users (n=79). Multiple logistic regression explored the association between relative harm perceptions and nicotine-use status, adjusting for sociodemographic variables. Results Over half of respondents perceived IQOS as equally or more harmful than e-cigarettes (53.7%), while almost a quarter either reported IQOS as less harmful than e-cigarettes or were uncertain (22.7% and 23.5%, respectively). Two-thirds of respondents (65.7%) perceived e-cigarettes as less harmful than cigarettes, yet only half (48.1%) perceived IQOS as less harmful than cigarettes. Both exclusive and dual e-cigarette users, but not exclusive smokers, had higher odds of perceiving IQOS as more harmful than e-cigarettes and less harmful than cigarettes compared to non-users. Conclusions Most nicotine users and non-users perceive differential health risk across IQOS, e-cigarettes, and cigarettes. Although e-cigarettes are generally viewed as less harmful than cigarettes, the perceived harm of IQOS was unclear. more...

Abstract Background Population-based studies suggest increasing rates of concurrent use of vaping products that contain either nicotine or cannabinoids. The aim of this pilot study was to test in vitro the acute inhalation toxicity of vaporized flavored and unflavored nicotine solutions co-administered with cannabidiol (CBD). Methods Bronchial epithelial cells (H292) were exposed directly to aerosol generated from electronic cigarettes refilled with propylene glycol only, unflavored nicotine solutions in propylene glycol with and without CBD, as well as to solutions containing only CBD. Cells were also exposed to a commercially available flavored solution containing nicotine and CBD. The in vitro toxicological effects were assessed after exposure using the following methods: 1) a trypan blue exclusion assay (cell viability), 2) neutral red uptake assay (metabolic activity) and 3) ELISA (concentrations of inflammatory mediators). Results Unflavored solution containing only CBD was significantly more cytotoxic than unflavored solution containing only nicotine. Unflavored solution containing both CBD and nicotine was significantly more cytotoxic than unflavored solutions with only nicotine. Levels of released cytokines were significantly higher when cells were co-exposed to nicotine and CBD as compared to cells exposed to only nicotine or only CBD. Overall, flavored products showed increased toxicity as compared to unflavored solutions. Conclusions This pilot in vitro study suggests independent and additive toxic effects of vaporized nicotine and CBD. Observed toxic effects are accentuated by flavorings. Future studies are needed to determine the potential long-term health consequences of concurrent use of vaporized nicotine and cannabis products. more...

Numerous flavoring chemicals are added to e-cigarette liquids to create various flavors. Flavorings provide sensory experience to users and increase product appeal; however, concerns have been raised about their potential inhalation toxicity. Estimating potential health risk of inhaling these chemicals has been challenging since little is known about their actual concentrations in e-cigarette products. To date, a limited number of analytical methods exist to measure the concentrations of flavoring chemicals in e-cigarette products. We have developed an analytical method that accurately and precisely measures the concentrations of 20 flavoring chemicals of potential inhalation risk concerns: 2,3,5-trimethylpyrazine, acetoin, benzaldehyde, benzyl alcohol, butanoic acid, dl-limonene, ethyl maltol, ethyl salicylate, ethyl vanillin, eucalyptol, eugenol, furaneol, isovanillin, l-menthol, maltol, methyl salicylate, pulegone, trans-cinnamaldehyde, triacetin, and vanillin. Calibration and QC solutions were prepared in 50:50 propylene glycol (PG):vegetable glycerin (VG) and 5% H2O and flavoring concentrations ranging from 0.02 to 10.00 mg/ml. Samples of commercial e-cigarette liquids, calibration and QC solutions were combined with 30 µL of an internal standard mix (benzene-d6, pyridine-d5, chlorobenzene-d5, naphthalene-d8 and acenaphthene-d10; 1 mg/ml each) and were diluted 100-fold into methanol. Analysis was performed on an Agilent 7890B/7250 GC/Q-TOF using a DB-624UI column (30 m x 0.25 mmID x 1.4 μm film thickness), with a total runtime of 13.5 min. Calibration curves were fit using a weighted quadratic model and correlations of determination (r2) values exceeded 0.990 for all chemicals. Bias and precision tests yielded values less than 20% and lower limits of quantitation (LLOQ) ranged from 0.02 to 0.63 mg/ml. Over 200 commercially available products, purchased or collected from adult e-cigarette users and spanning a range of flavor categories, were evaluated with this method. Concentrations of pulegone, a suspected carcinogen, varied from below limit of quantitation (BLOQ) to 0.32 mg/ml, while acetoin and vanillin, known precursors to more cytotoxic byproducts, ranged from BLOQ to 1.52 mg/ml and from BLOQ to 16.22 mg/ml, respectively. This method features a wide dynamic working range and allows for a rapid routine analysis of flavoring additives in commercial e-cigarette liquids. more...

Introduction: Although electronic cigarettes (e-cigarettes) were originally developed to deliver aerosolized nicotine to lungs, recent data have shown that consumers also use them for inhalation of other drugs, including cannabidiol (CBD). The aim of this study was to test the acute inhalation toxicity of flavored CBD-containing aerosols emitted from e-cigarettes.Methods: Bronchial epithelial cells (H292) cells were exposed to aerosol generated from e-cigarettes refilled either with (1) propylene glycol solvent only (PG, control), (2) commercially purchased unflavored solution with CBD, or (3) commercially purchased solutions with and without CBD and with different flavors. The in vitro toxicological effects were assessed using the following methods: (1) trypan blue exclusion assay (cell viability), (2) neutral red uptake assay (metabolic activity), and (3) ELISA (concentrations of inflammatory mediators).Results: Most flavored products with or without CBD were cytotoxic as compared to the air control. Overall, aerosols with CBD were more cytotoxic than aerosols without CBD irrelevant of the flavoring used in the product. Although, unflavored aerosols containing CBD in PG were significantly more cytotoxic than aerosols containing only PG, not all flavored products containing CBD were significantly more toxic than the same flavored products without CBD. Most CBD containing products significantly increase the concentration of cytokines released as compared to the same flavored products without CBD.Conclusion: Different flavors show different cytotoxic effects in CBD-containing e-cigarettes. Aerosols emitted from CBD containing e-cigarettes were more cytotoxic than those emitted from CBD-free e-cigarettes. more...

Background: Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants formed from incomplete combustion of organic matter; some PAHs are carcinogens. Smoking, diet, and other activities contribute to exposure to PAHs. Exposure data to PAHs among combustible tobacco product users (e.g. cigarette smokers) exist; however, among non-combustible tobacco products users (e.g., e-cigarette users), such data are rather limited. Objectives: We sought to evaluate exposure to PAHs among participants in Wave 1 (2013–2014) of the Population Assessment of Tobacco and Health (PATH) Study based on the type of tobacco product (combustible vs non-combustible), and frequency and intensity of product use. Methods: We quantified seven PAH urinary biomarkers in 11,519 PATH Study participants. From self-reported information, we categorized 8327 participants based on their use of tobacco products as never-tobacco user (never user, n = 1700), exclusive current established combustible products user (combustible products user, n = 5767), and exclusive current established non-combustible products user (non-combustible products user, n = 860). We further classified tobacco users as exclusive cigarette user (cigarette user, n = 3964), exclusive smokeless product user (SLT user, n = 509), and exclusive e-cigarette user (e-cigarette user, n = 280). Last, we categorized frequency of product use (everyday vs some days) and time since use (last hour, within 3 days, over 3 days). We calculated geometric mean (GM) concentrations, and evaluated associations between tobacco product user categories and PAH biomarkers concentrations. Results: Combustible products users had significantly higher GMs of all biomarkers than non-combustible products users and never users; non-combustible products users had significantly higher GMs than never users for four of seven biomarkers. For all biomarkers examined, cigarette users had the highest GMs compared to other tobacco-product users. Interestingly, GMs of 2-hydroxyfluorene, 3-hydroxyfluorene and ∑2,3-hydroxyphenanthrene were significantly higher in SLT users than in e-cigarette users; 3-hydroxyfluorene and 1-hydroxypyrene were also significantly higher in e-cigarette and SLT users than in never users. Everyday cigarette and SLT users had significantly higher GMs for most biomarkers than some days' users; cigarette and SLT users who used the product in the last hour had significantly higher GMs of most biomarkers than other occasional cigarette or SLT users respectively. By contrast, everyday e-cigarette users' GMs of most biomarkers did not differ significantly from those in some days' e-cigarette users; we did not observe clear trends by time of last use among e-cigarette users. Conclusions: Users of tobacco products had higher PAH urinary biomarker concentrations compared to never users, and concentrations differed by type and frequency of tobacco product use. more...

Research examining relationships between protective health behaviors and tobacco use offers valuable insight regarding the behavior profiles of product users. In particular, protective health behavior trends among adolescent e-cigarette users have not been examined thoroughly to date. This study investigates physical activity patterns among adolescent e-cigarette users, smokers, and dual users of both products, as compared with never users of tobacco products.Data were collected from 8383 youth participants (12–17 years of age) enrolled in Wave 2 (2014–2015) of the nationally-representative Population Assessment of Tobacco and Health Study. Relationships between use of tobacco products and physical activity were examined via weighted multivariable logistic regression procedures. Compared with never users, each product use group demonstrated an increased likelihood to abstain from moderate-vigorous physical activity. While dual users (aOR = 0.52; 95% CI: 0.30–0.85) and smokers (aOR = 0.53; 95% CI: 0.35–0.71) were less likely than never users to participate in vigorous physical activity, no differences were observed between e-cigarette and never users (aOR = 1.04; 95% CI: 0.74–1.47). Dual users consistently demonstrated the lowest likelihood of physical activity participation.In conclusion, e-cigarette users were more likely to abstain from moderate-vigorous physical activity participation than never users. However, results did not indicate differences in vigorous or muscle-strengthening physical activity participation between e-cigarette users and never users. Though findings specific to moderate-vigorous physical activity demonstrate a behavioral similarity between e-cigarette users and smokers, key differences in vigorous physical activity were observed. Comparatively low physical activity among dual users suggests existence of a behavior profile gradient according to product use. Keywords: Physical activity, e-Cigarettes, Smoking, Adolescent, Youth more...

Background: E-liquids are commercially available and manufactured, however some users of e-cigarettes prefer to prepare them at home (Do-it-Yourself; DIY) using individual ingredients. To date there is a paucity of research on how and why users make their own e-liquids. Methods: Forty-one European and US based exclusive users of e-cigarettes (ex-smokers) were individually interviewed. Structured interviews focused on motivations for home-mixing, practices, buying habits and broader themes around reasons for long-term vaping. We also measured nicotine and solvent concentrations and analysed 33 DIY e-liquids collected from 16 participants for nicotine, solvents, flavourings, and potentially harmful chemicals. Results: There were four main reasons for DIY: 1) economical (financial savings), 2) self-control over manufacturing process, 3) novelty, fun and 4) higher nicotine concentrations. Twelve out of 16 participants achieved nicotine concentration within 20% of their intended limit. Samples from five participants were above the EU Tobacco Products Directive's (TPD) 20 mg/ml nicotine concentration upper limit. Most samples contained more vegetable glycerine (VG) than propylene glycol (PG) and the most commonly used flavourings were dessert, e.g., vanilla and caramel. Chemical analysis also revealed presence of several potentially harmful chemicals and respiratory irritants, including cinnamaldehyde, benzaldehyde, and acetoin. Conclusion: DIY may offer users of e-cigarettes a long-term affordable practical method of vaping. Recommended safety advice needs to reflect actual and fast moving user behaviour. Keywords: E-liquid, E-cigarettes, Vaping, Home-made liquids, DIY liquids, Harmful and potentially harmful chemicals more...

Background Smoke-free indoor air policy has been widely adopted in some regions of the United States in order to protect bystanders from the deleterious effects of indoor tobacco smoke exposure; however, similar legislation has widely not been applied to ENDS devices. This study investigated differences in PM 2.5 matter emitted into the indoor environment from a selection of ENDS products under controlled conditions. Methods Sixteen smokers were recruited to vape in seven individual sessions (one visit per week). During each visit, participants vaped using one of seven different ENDS products. All vaping occurred within a dedicated exposure chamber. Volunteers drew twenty puffs on their assigned devices over a ten-minute exposure period. ENDS products tested included: disposable, e-cigar, vaporizer, rechargeable, e-pipe, and e-Go devices. TSI SidePaks were used to record both ambient and ENDS-associated unadjusted PM 2.5 before, during, and after each exposure period. Statistical analysis was performed using IBM SPSS Statistics Version 23. Results The rechargeable device emitted the highest amount of PM 2.5 (µg/m 3 ) on average (µ=21.6, σ=7.82). The disposable device emitted the lowest amount of PM 2.5 on average (µ=4.14, σ=1.09). The difference in PM2.5 matter in the smoking chamber during each session compared to ambient levels before each session was significant (p< 0.05) by paired t-test for all devices except e-pipe, which was borderline significant (p=0.053). The mean difference in PM 2.5 emissions between the rechargeable device was significantly from e-cigar (p=0.048), e-Go (p=0.048), and disposable (p=0.021) products. Conclusions This study found that ENDS devices emit levels of particulate matter into the indoor environment that are significantly higher than ambient PM 2.5 levels. Further, significant emission differences were also detected between ENDS products. These findings suggest that incorporating ENDS products into existing smoke-free indoor air policy would protect non-users from side-stream exposure to ENDS aerosol. more...

Background Electronic cigarettes (e-cigarettes) have risen in popularity in the U.S. While recent studies have described the prevalence and demographics of e-cigarette users, few studies have evaluated the impact of advertising on perceptions and interest in trial. This pilot study was conducted to assess whether exposure to ads for e-cigarettes or a comparison product (snus), elicited differences in interest to try e-cigarettes between smokers and non-smokers. Methods A web-based survey was completed by 600 respondents, aged 18–65, recruited from an internet panel in the U.S. Respondents answered questions assessing tobacco use, and then viewed nine magazine ads for Blu e-cigarettes or Camel snus, a low-nitrosamine smokeless tobacco product, in random order. After viewing each ad, respondents were asked a series of questions about their perceptions, beliefs, attitudes, and interest in trial. At the end, respondents were asked to choose a free sample product from the following options: an e-cigarette, smokeless tobacco (SLT), pack of cigarettes, or no product. Results Ad receptivity scores did not appear to be influenced by ad theme; differences existed between smokers and non-smokers. Participants exposed to e-cigarette ads more frequently reported favorable product attitudes compared to participants exposed to snus ads. Cigarette smokers in the e-cigarette condition were more likely to report interest in trying e-cigarettes compared to non-smokers in that condition (p-value more...