|Year : 2022 | Volume
| Issue : 1 | Page : 6-18
E-cigarettes: An emerging threat to the respiratory health of our next generation
Caitlin Hon Ning Yeung
Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
|Date of Submission||05-Oct-2021|
|Date of Decision||09-Jan-2022|
|Date of Acceptance||08-May-2022|
|Date of Web Publication||02-Jan-2023|
Ms. Caitlin Hon Ning Yeung
Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR
Source of Support: None, Conflict of Interest: None
Introduction: Given dramatic rises in electronic cigarette (e-cigarette) use among adolescents and ongoing dilemmas regarding their harms versus potential for harm reduction, this study examined the current pattern of e-cigarette use, the perceived health effects of e-cigarettes and the association of e-cigarette with the use of other tobacco products among Hong Kong secondary school students. Materials and Methods: 26,684 Hong Kong secondary school students participated in the territory-wide, school-based Hong Kong Secondary School Smoking and Health Survey 2016/17, conducted by the HKU School of Public Health. Data regarding demographics, self-reported harms of e-cigarette use, and its association with smoking intention, habits and quitting intention, was obtained and analysed. Results: Among Hong Kong secondary school students, 8.9% have ever-used e-cigarettes and the prevalence of past-30-day e-cigarette use was 3.0%. For those who had ever used e-cigarettes, 27.1% had their first puff before or at 11 years old. E-cigarette use among secondary school students was significantly associated with chronic respiratory symptoms (current users: AOR 1.59, 95% CI 1.13–2.23; ever users: AOR 1.36, 95% CI 1.22–1.53) and poorer perceived health status (current users: AOR 1.57, 95% CI 1.08–2.27; ever users: AOR 1.33, 95% CI 1.14–1.56), after adjusting for confounders. Current adolescent e-cigarette use was also significantly associated with increased intentions of tobacco smoking (AOR 1.17, 95% CI 1.12–2.46) and waterpipe use (AOR 2.63, 95% CI 1.77–3.91) in the next 12 months, cigarette smoking status (including those who ever-smoked, experimented, quit and currently smoke), and waterpipe and other tobacco product use in the past 30 days. Moreover, Hong Kong secondary school students who used e-cigarettes along with cigarettes did not show significant changes in quitting intention. Conclusions: E-cigarette use was associated with poorer perceived health status and respiratory symptoms, increased use and intention to use cigarettes and other tobacco products, and no significant changes in quitting intention. This study does not support e-cigarettes as a harm reduction tool and shows that e-cigarettes are not safe as general consumer products. Their function as a gateway to smoking and their failure to reduce quitting intention in adolescents may renormalize the tobacco industry and reverse all tobacco control efforts.
Keywords: E-cigarettes, electronic cigarettes, gateway, respiratory health, smoking cessation
|How to cite this article:|
Yeung CH. E-cigarettes: An emerging threat to the respiratory health of our next generation. Pediatr Respirol Crit Care Med 2022;6:6-18
|How to cite this URL:|
Yeung CH. E-cigarettes: An emerging threat to the respiratory health of our next generation. Pediatr Respirol Crit Care Med [serial online] 2022 [cited 2023 Feb 8];6:6-18. Available from: https://www.prccm.org/text.asp?2022/6/1/6/366613
| Introduction|| |
Tobacco is the top preventable cause of respiratory morbidity and mortality worldwide. Whilst Hong Kong’s tobacco smoking rates has been on the decline over the past few decades, ranking amongst the lowest in the world at 10.0%, a new potential threat to respiratory health of our next generation has emerged.
Electronic cigarettes (e-cigarettes) are devices that facilitate nicotine intake through a vaporized ‘e-liquids’, consisting of varying levels of nicotine, flavorings and additives, without tobacco combustion. Global e-cigarettes usage surged from 7 to 35 million within 5 years between 2011–2016, and is projected to rise even further to 55 million by 2021. In 2017, the Tobacco Control Policy-related Survey by the Hong Kong Council on Smoking and Health (COSH) showed that 3.5% of respondents have ever used e-cigarettes. Yet, it was alarming to note that 37.4% of e-cigarette users were adolescents aged 15–29, which was drastically more than any other age group.
The rapidly growing youth and adolescent e-cigarette user-base, bolstered by successful youth-directed marketing with diverse e-cigarette packaging and flavor choices, is especially concerning. In 2016/17, the prevalence of e-cigarette use among secondary and primary students were 8.7% and 1.4% respectively. In particular, a local study revealed that the percentage of Primary 2 to 4 pupils who had tried e-cigarettes increased by 55% within a year from 2016/17 to 2017/18. Given that substance use is typically established during early adolescence, it is important to develop a greater understanding on the impact of e-cigarette usage amongst youths due to its implications on their short-term and long-term health.
However, there have been fervent debates over whether e-cigarettes are in fact harm-reducing or harm-inducing. E-cigarettes have been marketed as healthier alternatives for cigarettes that could also aid smoking cessation. On the other hand, numerous public health experts around the world have been calling for a ban on e-cigarettes, citing mounting evidence of its negative health impact and potential as a gateway to nicotine addiction and youth smoking. Hence, this study was conducted among Hong Kong secondary school students with the following objectives:
- To assess the current pattern of e-cigarette use among HK secondary school students
- To analyze the perceived health effects of e-cigarettes among Hong Kong secondary school students
- To evaluate the association of e-cigarette with the use of other tobacco products among Hong Kong adolescents
| Materials and Methods|| |
A territory-wide, school-based survey on smoking among Secondary 1 to 6 students was conducted by the HKU School of Public Health in 2016–17. Data regarding demographics, self-reported harms of e-cigarette use, and its association with smoking intention, habits and quitting intention, was obtained. SPSS Statistics 25 was used for analysis. Sociodemographic characteristics and e-cigarette smoking behaviour were summarized using descriptive statistics. Chi-squared tests were used to compare factors associated with e-cigarette use, intention of use, health effects and associations with other tobacco products. Adjusted odds ratios (AOR) were calculated using logistic regression, adjusting for age, sex, place of birth, perceived family affluence, parental education, housing type, and, where appropriate, cigarette smoking status or use of other tobacco products in the past 30 days.
| Results|| |
Pattern of e-cigarette use
A total of 26,684 secondary school students participated in the survey. Baseline characteristics are described in [Table 1].
Among Hong Kong secondary school students, 8.9% have ever-used e-cigarettes and the prevalence of past-30-day e-cigarette use was 3.0%. For those who had ever used e-cigarettes, 30.4% had smoked in the past 30 days and 5.3% were frequent users (i.e. used e-cigarettes for more than 20 days in the past 30 days). 27.1% had their first puff before or at 11 years old (primary school age), and 86.9% before 16 years old [Table 2].
The major reasons cited for using e-cigarettes were ‘easy to use at home unnoticed’ (19.8%), ‘curiosity’ (17.2%), ‘like the flavours’ (10.6%), ‘attractive and trendy’ (7.9%), and ‘less harmful to health’ (4.1%). 48.1% of e-cigarette users did not know whether their e-cigarettes contained nicotine. 24.5% never, 15.7% occasionally and 11.7% always used nicotine-containing e-cigarettes. Fruits were the most popular flavour among youth (43.4%), followed by mint (19.0%) and candy (12.2%). Only 3.1% smoked e-cigarettes with no flavour [Table 3].
Among those who did not use e-cigarettes, 9.8% were susceptible to use (i.e. did not have strong determination to not use e-cigarettes), and 3.9% had intentions to use e-cigarettes in the next 12 months [Table 2]. Sociodemographic factors associated with a greater intention to use e-cigarettes among non-users in the next 12 months were older age, male sex, below-average perceived family affluence, living in public/subsidized housing [Table 4]. The intention to use e-cigarettes also significantly increased with increasing number of peers using e-cigarettes, especially perceiving that 5 or more peers use e-cigarettes, as well as e-cigarette use in any family member, including father, mother, siblings, other relatives or maids (all P < 0.001) [Table 5]. Those who perceived e-cigarettes more positively and believed that e-cigarettes were not harmful were also significantly more likely to have intentions of using e-cigarettes. The most commonly cited favourably perceptions that were associated with increased intentions to use were ‘better acceptance’ (AOR 6.032, 95% CI 4.525–8.039), ‘attractive and trendy’ (AOR 3.72, 95% CI 3.04–4.55) and ‘having fewer harms’ (AOR 3.51, 95% CI 2.89–4.28) [Table 6].
|Table 4: Association of sociodemographic factors with e-cigarette use and intention of use|
Click here to view
|Table 6: Association of perceptions of e-cigarettes with e-cigarette use and intention of use|
Click here to view
Health effects of e-cigarette use
[Table 7] shows the association of e-cigarette usage with respiratory symptoms. Among secondary school students, 29.3% of ever e-cigarette users and 34.4% of current users reported having respiratory symptoms, such as cough or sputum, for over 3 months in the past year, as compared to 23.2% among all students. E-cigarette use was significantly associated with having chronic respiratory symptoms, including ever-users (AOR, 1.36; 95% CI, 1.22–1.53), experimenters, and current users (AOR 1.59, 95% CI 1.13–2.23).
As for self-perceived health status, 24.8% of e-cigarette ever-users and 39.3% current users reporting fair to poor health (versus good to excellent), as compared to 15.1% among all secondary school students. Poorer perceived health status was significantly associated with ever use (AOR, 1.33; 95% CI, 1.14–1.56) and current use of e-cigarettes (AOR, 1.57; 95% CI, 1.08–2.27). Significant associations were also observed in e-cigarette experimenters, ex-smokers and current daily users [Table 8].
Passive e-cigarette smoke exposure has also been shown to have significant health effects. Increased number of days of passive e-cigarette smoke exposure at home over the past 7 days was significantly associated with fair to poor perceived health status. Likewise, increased number of days of passive e-cigarette smoke exposure outside home over the past 7 days was significantly associated with fair to poor perceived health status and respiratory symptoms, as compared to good or excellent [Table 9].
|Table 9: Health effects of passive e-cigarette smoke exposure in never-users|
Click here to view
The health effects of e-cigarettes were also compared to traditional cigarettes. E-cigarettes are generally perceived as less harmful and viewed more positively than cigarettes (both p-values<0.001) [Table 10]. While the percentage of cigarette smokers who had poorer perceived health status (38.3%) and respiratory symptoms (39.2%) were indeed higher than e-cigarette smokers (27.4% for perceived health status and 31.2% respiratory symptoms), no significant differences were observed between current cigarette and e-cigarette smokers’ perceived health status (AOR, 1.49; 95% CI, 0.90–2.46) and respiratory symptoms (1.59, 0.97–2.62) [Table 11].
Association between e-cigarettes and other tobacco products
The association between e-cigarette, cigarettes and other tobacco products is explored in [Table 12]. For those who had never used e-cigarettes, the majority (92.5%) never smoked cigarettes, while 5.5% experimented, 1.3% quit and 0.7% were current smokers. Yet among current e-cigarette users, the majority (61.0%) concurrently smoked cigarettes, as compared to 20.7% who had quit, 10.4% who experimented and 7.9% who had never smoked cigarettes. Moreover, among current e-cigarette users, 38.4% used cigarettes, 19.2% used waterpipes and 59.6% used other tobacco products in the past 30 days.
Current e-cigarette use was significantly associated with the intention to smoke cigarettes (AOR, 1.17; 95% CI, 1.12–2.46) and waterpipes (2.63, 1.77–3.91). Current use also significantly increased odds of ever (15.09, 7.35–30.97), experimented (11.54, 5.26–25.32), quit (16.58, 7.07–38.91) and current tobacco smoking status (45.02, 19.24–105.38). Moreover, current e-cigarette use was significantly associated with cigarette (AOR: 1.73, 1.02–2.96), waterpipe (AOR: 3.71, 1.82–7.57) and other tobacco product dual use (13.83, 9.56–20.02) [Table 13].
|Table 13: Association of e-cigarette use with smoking intention and status|
Click here to view
Regarding the temporality and effects of e-cigarette use on cigarette smoking, 38.7% of those who had ever tried both cigarettes and e-cigarettes stated that they used e-cigarettes first. Out of all of the reasons to start smoking cigarettes, 21.0% believed that e-cigarette use caused their cigarette smoking. As for the effect of e-cigarette use on cigarette smoking, 58.8% of respondents reported no change or increased cigarette smoking after using e-cigarettes. Only 23.1% quit smoking and 18.1% smoked fewer cigarettes [Table 14].
|Table 14: Temporality and effect of e-cigarette use on cigarette smoking|
Click here to view
Although e-cigarettes are marketed as a smoking cessation aid, using e-cigarettes in addition to cigarettes, as compared to just smoking cigarettes, did not show any significant difference in quitting intention (AOR, 1.02; 95% CI, 0.54–1.91). Negative but non-significant associations were shown in number of quit attempts in the past 12 months (0.88, 0.76–1.02), total number of quit attempts (0.95, 0.83–1.09) and duration of the longest quit attempt (0.99, 0.92–1.08) in dual users compared with just cigarette smokers [Table 15].
|Table 15: Association of cigarette and e-cigarette usage with quitting intention|
Click here to view
| Discussion|| |
The prevalence of past-30-day use (3.0%) and ever-use (8.9%) of e-cigarettes among Hong Kong secondary school students in 2016/17 were low compared with most Western countries. During the same time period, 11.3% of US high school students, 25% of those aged 11–15 in England and 6.3% of Canadians aged 15–19 used e-cigarettes in the past 30 days. Ever-use of e-cigarettes was 27.1% in US adolescents, 20.0% in New Zealand, 7.1% in Australia and 7–18% across the UK. As for Asian countries, e-cigarette ever-use among adolescents was also higher in Japan and Korea (9.4%), but lower in China (3.1%) and Taiwan (2.2%).,
However, the past-30-day use prevalence (3.0%) in 2016/17 indicates a 272% increase from 1.1% in 2012/13. The tripling of e-cigarette use in youth reflects a global pattern seen in other countries, including the US, Canada, Poland and New Zealand. Moreover, substantial growth in e-cigarette use opposes the decline of cigarette smoking in Hong Kong over the past few decades, which is among the lowest globally at 10.0%. To illustrate, e-cigarettes have overtaken cigarettes as the most popular smoking device among teenagers in the US in 2019, with youth usage skyrocketing by 78% within 1 year. This trend will likely be echoed in Hong Kong if this emerging device is not regulated.
Moreover, almost one in three e-cigarette users had their first e-cigarette puff during primary school age (≤11 years old), which concurs with a local study showing a striking 55% increase in Primary 2–4 pupils who had used e-cigarette within a year. These results are particularly concerning as those who started e-cigarettes early were more likely to be current and frequent users, use nicotine-containing e-cigarettes and other tobacco products. This will likely extend into adulthood and have severe impacts on their short-term and long-term health.
In Hong Kong, secondary school students who had ever-used, quit or currently use e-cigarettes were significantly more likely to have poorer perceived health than never-users, after adjusting for confounders including smoking status. All levels of e-cigarette use also significantly increased respiratory symptoms, corroborating with earlier local findings that showed significant associations between past-30-day use and respiratory symptoms. This adds to existing evidence of increased cough, wheezing and asthma exacerbations in adolescent e-cigarette users.,,, Findings are also coherent across animal and in-vitro systems, which suggest that respiratory symptoms are likely associated with increased oxidative stress, cellular inflammation, suppressed cough reflexes and impaired muco-ciliary clearance induced by e-cigarette aerosols.,,,,,
These results bolster the mounting evidence regarding the health risks of e-cigarettes. E-cigarettes have previously been endorsed by Public Health England and the Royal College of Physicians as harm reduction tools with 95% lower risk than smoking, which explains the more positive perceptions of e-cigarettes among secondary school students. However, these findings have since been criticized for drawing conclusions based on inadequate evidence, and no significant difference between Hong Kong secondary-school cigarette and e-cigarette users was found regarding their perceived health status and respiratory symptoms. Although exposure to certain toxic ingredients commonly found in cigarettes is indeed lower in e-cigarettes,,,,, this does not mean that e-cigarettes are safe as general consumer products.
E-cigarette liquids and aerosols contain numerous toxic substances, including several known carcinogens (e.g. formaldehyde, acrolein) that support the possibility of increase cancer risk and adverse reproductive outcomes from long-term exposure.,,,, Nicotine exposures are comparable to combustible tobacco cigarettes,, which leads to nicotine addiction and damages the developing adolescent brain. Moreover, the number of heavy-metals, which are established to be highly toxic for multiple organ systems when inhaled, are greater in e-cigarette aerosols than in tobacco-cigarettes. Emerging evidence further demonstrates that e-cigarette usage increases the risk of long-term health outcomes, including emphysema, chronic bronchitis and COPD, stroke, myocardial infarction, angina and coronary heart disease, with a low probability of reverse causation. The biological plausibility of these long-term health consequences are supported by new research showing decreased production in nitric oxide that protect blood vessels, increased platelet function and thrombogenesis, along with existing evidence that arterial stiffness, blood pressure and heart rate increase shortly after e-cigarette use.,,,
Passive e-cigarette smoke exposure at home and outside were shown to negatively affect perceived health status and respiratory symptoms in secondary school students who never used e-cigarettes. Second-hand e-cigarette emissions contribute to indoor air pollution above WHO recommended levels, although less so than second-hand tobacco smoke. The chemical cocktail of nicotine, diacetyl flavourings which are linked to serious respiratory diseases, ultra-fine particles, volatile organic compounds and heavy metals from second-hand emissions can adversely affect health, especially in children, pregnant women, elderly and cardiorespiratory disease patients.
Gateway to tobacco
Regarding the association between e-cigarettes and tobacco-products, current adolescent e-cigarette use was significantly associated with increased intentions of tobacco smoking and waterpipe use in the next 12 months, cigarette smoking status (including those who ever-smoked, experimented, quit and currently smoke), and waterpipe and other tobacco product use in the past 30 days. Moreover, 2 in 5 of those who ever tried both cigarettes and e-cigarettes said they used e-cigarettes before cigarettes, and 21% believed that e-cigarette use caused their cigarette smoking. These findings all support e-cigarettes as a gateway to youth smoking and other tobacco product use, in line with large scale systematic reviews and studies conducted locally and abroad.,,,,,, The majority of respondents also reported no change or increases in cigarette smoking after e-cigarette use, rather than reducing or quitting smoking. Positive correlation between e-cigarette use and cigarette smoking frequency and intensity is also documented in literature, with subsequent analysis showing that adolescent non-smokers who used e-cigarettes with higher nicotine concentrations were subsequently more likely to smoke more frequently.,
Despite being marketed as a smoking cessation tool, Hong Kong secondary school students who used e-cigarettes along with cigarettes did not show significant changes in quitting intention. Total number of quit attempts, number of quit attempts in the past year and duration of longest quit attempts were non-significantly lower in dual users than those who just smoked cigarettes. This supports WHO’s decision to reject e-cigarettes as an effective smoking cessation tool, especially given that ‘wanting to quit or reduce smoking’ ranked among the least-cited reasons for using e-cigarettes in HK adolescents. Moreover, among current e-cigarette users, twice as many concurrently smoked cigarettes (61.0%) compared to those who experimented or quit smoking (31.1%), indicating dual use of e-cigarettes and cigarettes was much more likely than quitting smoking.
Conversely, a recent randomized trial showed that sustained abstinence was higher among e-cigarette users (18.0%) than nicotine-replacement therapy (9.9%), concluding that e-cigarettes are efficient smoking cessation tools. However, upon further analysis, nicotine-free abstinence rates were in fact lower among e-cigarette users (3.7%) compared to those who received nicotine-replacement therapy (9.0%), with significant dual use among those who failed to quit. While there is no available data regarding the long-term health effects of dual use, it is likely that having two sources of nicotine can lead to effect multiplication on the harms. Nonetheless, current evidence is inadequate to conclude that e-cigarettes are effective smoking cessation aids. More research is needed to determine the effectiveness and feasibility of medicalising e-cigarettes as a restricted smoking cessation tool in Hong Kong.
Limitations and generalizability
There are various limitations to this study. First, the study was based on self-reported data which is subject to reporting biases. Second, the cross-sectional design does not permit causality inference on the temporal relationship between e-cigarette use and independent variables. Nonetheless, the large territory-wide, school-based sample and appraisal of a wide range of factors affecting e-cigarette use in secondary school students suggest that these results can be generalizable to the Hong Kong adolescent population.
| Conclusion|| |
Overall, the tripling of e-cigarette use and substantial early initial in recent years is extremely concerning. This report does not support e-cigarettes as a harm reduction tool and shows that e-cigarettes are not safe as general consumer products. Moreover, their function as a gateway to smoking and reduction of quitting intention in adolescents may renormalize the tobacco industry and reverse all tobacco control efforts. Above all, as the potential harms of e-cigarettes are not completely understood, the precautionary principle should apply to protect the general public from exposures to the harms of e-cigarettes until further scientific findings emerge.
The use of tobacco products, including e-cigarettes, continues to be a major health threat to children, adolescents and adults. If the current trend of e-cigarette use among adolescents continues, the achievements in tobacco control would be completely undermined. Given the unique role of paediatricians on influencing child and adolescent health in their early stages of development, paediatricians should counsel children and adolescents on the risks of e-cigarette use, and advise parents and caregivers who smoke or use e-cigarettes about quitting. Moreover, healthcare professionals should advocate for e-cigarette control policies to nip the growing e-cigarette epidemic in the bud. The proposed legislation to ban e-cigarette sales, distribution, importation, advertising and use in smoking-free areas should be passed as soon as possible to protect the health of our next generation.
I would like to thank my Master of Public Health supervisor Dr. Ho Sai Yin Daniel from the HKU School of Public Health and the University of Hong Kong for access to data of the Hong Kong Secondary School Smoking and Health Survey 2016/17, as well as his supervision and guidance.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Hong Kong Council on Smoking and Health. Smoking Prevalence for Males and Females in Hong Kong 2018. Available from: https://www.chp.gov.hk/en/healthtopics/content/25/8806.html#
[Last accessed on 2022 May 17].
Caponnetto P, Campagna D, Papale G, Russo C, Polosa R. The emerging phenomenon of electronic cigarettes. Expert Rev Respir Med 2012;6:63-74.
Jones L. Vaping - the rise in five charts. BBC News. 2018. Available from: https://www.bbc.com/news/business-44295336
. [Last accessed on 2022 May 17].
Hong Kong Council on Smoking and Health. Report on Tobacco Control Policy-related Survey 2017.2017. [Available from: http://www.smokefree.hk/UserFiles/resources/about_us/cosh_reports/COSHRN_E24.pdf
. [Last accessed on 2019 May 3].
Grana RA, Ling PM. “Smoking revolution”: A content analysis of electronic cigarette retail websites. Am J Prev Med 2014;46:395-403.
Hong Kong Council of Smoking and Health. (June 2018) Press Release - Enact a total ban on e-cigarettes and other new tobacco products for the sake of public health. Available from: https://www.smokefree.hk/en/content/web.do?page=pr20180615
. [Last accessed on 2019 May 3].
Jiang N, Wang MP, Ho SY, Leung LT, Lam TH. Electronic cigarette use among adolescents: A cross-sectional study in Hong Kong. BMC Public Health 2016;16:202.
National Center for Chronic Disease Prevention and Health Promotion (US) Office on Smoking and Health. E-Cigarette Use Among Youth and Young Adults: A Report of the Surgeon General (US) AGCfDCaP, editor. 2016. Available from: https://www.cdc.gov/tobacco/data_statistics/sgr/e-cigarettes/index.htm
. [Last accessed on 2022 May 17].
Ndunda PM, Muutu TM. Abstract 9: Electronic cigarette use is associated with a higher risk of stroke. Stroke 2019;50:A9.
Siddiqui F, Mishu M, Marshall AM, Siddiqi K. E-cigarette use and subsequent smoking in adolescents and young adults: A perspective. Expert Rev Respir Med 2019;13:403-5.
Ontario Agency for Health Protection and Promotion (Public Health Ontario). Berenbaum E, KellerOlaman S, Manson H, Moloughney B, Muir S, Simms C, et al
. Current evidence on ecigarettes: A summary of potential impacts. Toronto: Queen’s Printer for Ontario; 2018.
Gentzke AS, Creamer M, Cullen KA, Ambrose BK, Willis G, Jamal A, et al
Vital Signs: Tobacco product use among middle and high school students — United States, 2011–2018. MMWR Morb Mortal Wkly Rep 2019;68:157-64.
White J, Li J, Newcombe R, Walton D. Tripling use of electronic cigarettes among New Zealand adolescents between 2012 and 2014. 2015;56:522-8.
Greenhalgh E, Scollo MM. InDepth 18B: Electronic cigarettes (e-cigarettes). In Scollo, MM, Winstanley, MH, editors. Tobacco in Australia: Facts and Issues. Melbourne: Cancer Council Victoria; 2017.
Bauld L, MacKintosh AM, Eastwood B, Ford A, Moore G, Dockrell M, et al
. Young people’s use of e-cigarettes across the United Kingdom: Findings from five surveys 2015–2017. Int J Environ Res Public Health 2017;14:973.
Lee S, Grana RA, Glantz SA. Electronic cigarette use among Korean adolescents: A cross-sectional study of market penetration, dual use, and relationship to quit attempts and former smoking. J Adolesc Health 2014;54:684-90.
Tabuchi T, Gallus S, Shinozaki T, Nakaya T, Kunugita N, Colwell B. Heat-not-burn tobacco product use in Japan: Its prevalence, predictors and perceived symptoms from exposure to secondhand heat-not-burn tobacco aerosol. Tob Control 2018;27:e25-33.
Chang HC, Tsai YW, Shiu MN, Wang YT, Chang PY. Elucidating challenges that electronic cigarettes pose to tobacco control in Asia: A population-based national survey in Taiwan. BMJ Open 2017;7:e014263.
Wang W, He Z, Feng N, Cai Y. Electronic cigarette use in China: Awareness, prevalence and regulation. Tob Induc Dis 2019;17:30.
Goniewicz ML, Gawron M, Nadolska J, Balwicki L, Sobczak A. Rise in electronic cigarette use among adolescents in Poland. J Adolesc Health 2014;55:713-5.
Hong Kong Council of Smoking and Health. COSH and Health Professionals Strongly Request for a Total Ban of Electronic Cigarettes. News Update 2018. Available from: https://www.smokefree.hk/page.php?id=581&lang=en
. [Last accessed on 2022 May 17].
Simon S. FDA Proposes Regulations as Teen E-Cigarette Use Skyrockets 78% in 1 Year. American Cancer Society 2018. Available from: https://www.cancer.org/latest-news/fda-proposes-regulations-as-teen-e-cigarette-use-skyrockets-78-percent-in-1-year.html#
. [Last accessed on 2022 May 17].
Wang MP, Ho SY, Leung LT, Lam TH. Electronic cigarette use and respiratory symptoms in chinese adolescents in hong kong. JAMA Pediatr 2016;170:89-91.
Cho JH, Paik SY. Association between electronic cigarette use and asthma among high school students in South Korea. Plos One 2016;11:e0151022.
Choi K, Bernat D. E-cigarette use among Florida youth with and without asthma. Am J Prev Med 2016;51:446-53.
Kumral TL, Saltürk Z, Yildirim G, Uyar Y, Berkiten G, Atar Y, et al
. How does electronic cigarette smoking affect sinonasal symptoms and nasal mucociliary clearance? B-Ent 2016;12:17-21.
McConnell R, Barrington-Trimis JL, Wang K, Urman R, Hong H, Unger J, et al
. Electronic cigarette use and respiratory symptoms in adolescents. Am J Respir Crit Care Med 2017;195:1043-9.
National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Population Health and Public Health Practice; Committee on the Review of the Health Effects of Electronic Nicotine Delivery Systems. In: Eaton DL, Kwan LY, Stratton K, editors. Public Health Consequences of E-Cigarettes. Washington, DC: National Academies Press; 2018.
Husari A, Shihadeh A, Talih S, Hashem Y, El Sabban M, Zaatari G. Acute exposure to electronic and combustible cigarette aerosols: Effects in an animal model and in human alveolar cells. Nicotine Tob Res 2016;18:613-9.
Hwang JH, Lyes M, Sladewski K, Enany S, McEachern E, Mathew DP, et al
. Electronic cigarette inhalation alters innate immunity and airway cytokines while increasing the virulence of colonizing bacteria. J Mol Med (Berl) 2016;94:667-79.
Laube BL, Afshar-Mohajer N, Koehler K, Chen G, Lazarus P, Collaco JM, et al
. Acute and chronic in vivo effects of exposure to nicotine and propylene glycol from an E-cigarette on mucociliary clearance in a murine model. Inhal Toxicol 2017;29:197-205.
Lerner CA, Sundar IK, Yao H, Gerloff J, Ossip DJ, McIntosh S, et al
. Vapors produced by electronic cigarettes and e-juices with flavorings induce toxicity, oxidative stress, and inflammatory response in lung epithelial cells and in mouse lung. PLoS One 2015;10:e0116732.
Lim HB, Kim SH. Inhallation of e-cigarette cartridge solution aggravates allergen-induced airway inflammation and hyper-responsiveness in mice. Toxicol Res 2014;30:13-8.
Sussan TE, Gajghate S, Thimmulappa RK, Ma J, Kim JH, Sudini K, et al
. Exposure to electronic cigarettes impairs pulmonary anti-bacterial and anti-viral defenses in a mouse model. PLoS One 2015;10:e0116861.
McNeill A, Brose LS, Calder R, Hitchman SC. E-cigarettes: An Evidence Update: A Report Commissioned by Public Health England. London: Public Health England; 2015.
Royal College of Physicians of London. RCP Statement on E-cigarettes. London: Royal College of Physicians; 2014.
McKee M, Capewell S. Evidence about electronic cigarettes: A foundation built on rock or sand? BMJ 2015;351:h4863.
Canistro D, Vivarelli F, Cirillo S, Babot Marquillas C, Buschini A, Lazzaretti M, et al
. E-cigarettes induce toxicological effects that can raise the cancer risk. Sci Rep 2017;7:2028.
Gillman IG, Kistler KA, Stewart EW, Paolantonio AR. Effect of variable power levels on the yield of total aerosol mass and formation of aldehydes in e-cigarette aerosols. Regul Toxicol Pharmacol 2016;75:58-65.
Kosmider L, Sobczak A, Fik M, Knysak J, Zaciera M, Kurek J, et al
. Carbonyl compounds in electronic cigarette vapors: Effects of nicotine solvent and battery output voltage. Nicotine Tob Res 2014;16:1319-26.
Papoušek R, Pataj Z, Nováková P, Lemr K, Barták P. Determination of acrylamide and acrolein in smoke from tobacco and e-cigarettes. Chromatographia 2014;77:1145-51.
Tayyarah R, Long GA. Comparison of select analytes in aerosol from e-cigarettes with smoke from conventional cigarettes and with ambient air. Regul Toxicol Pharmacol 2014;70:704-10.
Bekki K, Uchiyama S, Ohta K, Inaba Y, Nakagome H, Kunugita N. Carbonyl compounds generated from electronic cigarettes. Int J Environ Res Public Health 2014;11:11192-200.
Goniewicz ML, Boykan R, Messina CR, Eliscu A, Tolentino J. High exposure to nicotine among adolescents who use juul and other vape pod systems (‘pods’). Tob Control 2019;28:676-7.
Hess CA, Olmedo P, Navas-Acien A, Goessler W, Cohen JE, Rule AM. E-cigarettes as a source of toxic and potentially carcinogenic metals. Environ Res 2017;152:221-5.
Jensen RP, Luo W, Pankow JF, Strongin RM, Peyton DH. Hidden formaldehyde in e-cigarette aerosols. N Engl J Med 2015;372:392-4.
Uchiyama S, Ohta K, Inaba Y, Kunugita N. Determination of carbonyl compounds generated from the E-cigarette using coupled silica cartridges impregnated with hydroquinone and 2,4-dinitrophenylhydrazine, followed by high-performance liquid chromatography. Anal Sci 2013;29:1219-22.
Jackler RK, Ramamurthi D. Nicotine arms race: JUUL and the high-nicotine product market. Tobacco Control 2019;28:623-8.
Olmedo P, Goessler W, Tanda S, Grau-Perez M, Jarmul S, Aherrera A, et al
. Metal concentrations in e-cigarette liquid and aerosol samples: The contribution of metallic coils. Environ Health Perspect 2018;126:027010.
Perez MF, Atuegwu N, Mead E, Oncken C, Mortensen EM. E-cigarette use is associated with emphysema, chronic bronchitis and COPD. Am J Respir Crit Care Med 2018;197:A6245.
Qasim H, Karim ZA, Rivera JO, Khasawneh FT, Alshbool FZ. Impact of electronic cigarettes on the cardiovascular system. J Am Heart Assoc 2017;6:e006353.
Glantz SA, Bareham DW. E-cigarettes: Use, effects on smoking, risks, and policy implications. Annu Rev Public Health 2018;39:215-35.
American Heart Association. Study: E-cigarettes may damage blood vessels. American Heart Association News Stories 2018. Available from: https://www.heart.org/en/news/2018/11/05/study-ecigarettes-may-damage-the-heart
. [Last accessed on 2022 May 17].
Qasim H, Karim ZA, Silva‐Espinoza JC, Khasawneh FT, Rivera JO, Ellis CC, et al
. Short‐term e‐cigarette exposure increases the risk of thrombogenesis and enhances platelet function in mice. J Am Heart Assoc 2018;7:e009264.
Farsalinos K, Cibella F, Caponnetto P, Campagna D, Morjaria JB, Battaglia E, et al
. Effect of continuous smoking reduction and abstinence on blood pressure and heart rate in smokers switching to electronic cigarettes. Intern Emerg Med 2016;11:85-94.
Moheimani RS, Bhetraratana M, Yin F, Peters KM, Gornbein J, Araujo JA, et al
. Increased cardiac sympathetic activity and oxidative stress in habitual electronic cigarette users: Implications for cardiovascular risk. JAMA Cardiol 2017;2:278-84.
Polosa R, Morjaria JB, Caponnetto P, Battaglia E, Russo C, Ciampi C, et al
. Blood pressure control in smokers with arterial hypertension who switched to electronic cigarettes. Int J Environ Res Public Health 2016;13:1123.
St Helen G, Dempsey DA, Havel CM, Jacob P 3rd, Benowitz NL. Impact of e-liquid flavors on nicotine intake and pharmacology of e-cigarettes. Drug Alcohol Depend 2017;178:391-8.
Etter JF. Gateway effects and electronic cigarettes. Addiction 2018;113:1776-83.
Hammond D, Reid JL, Cole AG, Leatherdale ST. Electronic cigarette use and smoking initiation among youth: A longitudinal cohort study. CMAJ 2017;189:E1328-36.
Kong G, Morean ME, Cavallo DA, Camenga DR, Krishnan-Sarin S. Reasons for electronic cigarette experimentation and discontinuation among adolescents and young adults. Nicotine Tob Res 2015;17:847-54.
Leventhal AM, Strong DR, Kirkpatrick MG, Unger JB, Sussman S, Riggs NR, et al
. Association of electronic cigarette use with initiation of combustible tobacco product smoking in early adolescence. JAMA 2015;314:700-7.
Lydon DM, Wilson SJ, Child A, Geier CF. Adolescent brain maturation and smoking: What we know and where we’re headed. Neurosci Biobehav Rev 2014;45:323-42.
Schneider S, Diehl K. Vaping as a catalyst for smoking? An initial model on the initiation of electronic cigarette use and the transition to tobacco smoking among adolescents. Nicotine Tob Res 2016;18:647-53.
Wang MP, Ho SY, Leung LT, Lam TH. Electronic cigarette use and its association with smoking in Hong Kong chinese adolescents. Addict Behav 2015;50:124-7.
Leventhal AM, Stone MD, Andrabi N, Barrington-Trimis J, Strong DR, Sussman S, et al
. Association of e-cigarette vaping and progression to heavier patterns of cigarette smoking. JAMA 2016;316:1918-20.
Wills TA, Sargent JD, Gibbons FX, Pagano I, Schweitzer R. E-cigarette use is differentially related to smoking onset among lower risk adolescents. Tob Control 2016;26:534-9.
Hajek P, Phillips-Waller A, Przulj D, Pesola F, Myers Smith K, Bisal N, et al
. A randomized trial of E-cigarettes versus nicotine-replacement therapy. N Engl J Med 2019;380:629-37.
Read R, O’Riordan T. The precautionary principle under fire, environment. Sci Policy Sust Dev 2017;59:5,4-15.
Morean ME, Butler ER, Bold KW, Kong G, Camenga DR, Cavallo DA, et al
. Preferring more e-cigarette flavors is associated with e-cigarette use frequency among adolescents but not adults. PLoS One 2018;13:e0189015-e.
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11], [Table 12], [Table 13], [Table 14], [Table 15]