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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

BackgroundSMS text messages are affordable, scalable, and effective smoking cessation interventions. However, there is little research on SMS text message interventions specifically designed to support people who smoke to quit by switching to vaping. ObjectiveOver 3 phases, with vapers and smokers, we codeveloped and coproduced a mobile phone SMS text message program. The coproduction paradigm allowed us to collaborate with researchers and the community to develop a more relevant, acceptable, and equitable SMS text message program. MethodsIn phase 1, we engaged people who vape via Twitter and received 167 responses to our request to write SMS text messages for people who wish to quit smoking by switching to vaping. We screened, adjusted, refined, and themed the messages, resulting in a set of 95 that were mapped against the Capability, Opportunity, and Motivation–Behavior constructs. In phase 2, we evaluated the 95 messages from phase 1 via a web survey where participants (66/202, 32.7% woman) rated up to 20 messages on 7-point Likert scales on 9 constructs: being understandable, clear, believable, helpful, interesting, inoffensive, positive, and enthusiastic and how happy they would be to receive the messages. In phase 3, we implemented the final set of SMS text messages as part of a larger randomized optimization trial, in which 603 participants (mean age 38.33, SD 12.88 years; n=369, 61.2% woman) received SMS text message support and then rated their usefulness and frequency and provided free-text comments at the 12-week follow-up. ResultsFor phase 2, means and SDs were calculated for each message across the 9 constructs. Those with means below the neutral anchor of 4 or with unfavorable comments were discussed with vapers and further refined or removed. This resulted in a final set of 78 that were mapped against early, mid-, or late stages of quitting to create an order for the messages. For phase 3, a total of 38.5% (232/603) of the participants provided ratings at the 12-week follow-up. In total, 69.8% (162/232) reported that the SMS text messages had been useful, and a significant association between quit rates and usefulness ratings was found (χ21=9.6; P=.002). A content analysis of free-text comments revealed that the 2 most common positive themes were helpful (13/47, 28%) and encouraging (6/47, 13%) and the 2 most common negative themes were too frequent (9/47, 19%) and annoying (4/47, 9%). ConclusionsIn this paper, we describe the initial coproduction and codevelopment of a set of SMS text messages to help smokers stop smoking by transitioning to vaping. We encourage researchers to use, further develop, and evaluate the set of SMS text messages and adapt it to target populations and relevant contexts.

Abstract Background Smoking is extremely common amongst adults experiencing homelessness. To date, there is no nationally representative data on how tobacco dependence is treated and if and how smoking cessation is supported across the homeless sector. The aim of this study was to document smoking and e-cigarette policies of UK homeless services and identify areas of good practice and where improvements could be made. Methods A cross-sectional survey with homeless centre staff was conducted between June 2020-December 2020 totalling 99 homeless centres. Quotas were stratified based on population and service type across Scotland, Northern Ireland, Wales, and England. Interviews were conducted over the phone or online in a minority of cases. Survey questions were themed to assess, i) onsite smoking and e-cigarette (vaping) policies ii) screening and recording of smoking status, iii) cessation training and resources available to staff, iv) cessation support for service users. Results 92% accounted for smoking within their policies in some form (stand-alone policy (56%) or embedded within another health and safety policy (36%)). 84% allowed smoking in at least some (indoor and outdoor) areas. In areas where smoking was not allowed, vaping was also disallowed in 96% of cases. Staff smoking rates were 23% and 62% of centres reported staff smoked with service users. Just over half (52%) reported screening and recording smoking status and 58% made referrals to Stop Smoking Services (SSS), although established links with SSS were low (12%) and most centres did not provide staff training on supporting smoking cessation. Areas of good practice included regular offers of smoking cessation support embedded in routine health reviews or visits from SSS and offering tangible harm reduction support. Areas for improvement include staff training, staff smoking with service users and skipping routine screening questions around smoking. Conclusions Smoking is accounted for across different policy types and restricted in some areas within most settings. Smoking cessation support is not routinely offered across the sector and there is little involvement with the SSS.

Abstract Background Health messages on e-cigarette packs emphasise nicotine addiction or harms using similar wording to warnings on cigarette packs. These may not be appropriate for e-cigarettes which constitute a reduced risk alternative for smokers. This research aimed to (1) develop and test a selection of relative risk messages for e-cigarette products; (2) compare these to the two current EU Tobacco Products Directive (TPD) nicotine addiction messages; and (3) explore differences between smokers, non-smokers and dual users. Method Twenty-six messages focusing on either harm-reduction or cessation were developed and rated by multidisciplinary experts for accuracy, persuasiveness and clarity. The eight highest ranking messages were compared alongside the TPD messages in a sample of 983 European residents (316 smokers, 327 non-smokers, 340 dual users) on understandability, believability and convincingness. Results On all three constructs combined, the two TPD messages rated the highest, closely followed by four relative risk messages “Completely switching to e-cigarettes lowers your risk of smoking related diseases”, “Use of this product is much less harmful than smoking”, “Completely switching to e-cigarettes is a healthier alternative to smoking”, and “This product presents substantially lower risks to health than cigarettes” which did not differ statistically from the TPD messages. Non-smokers rated TPD1 significantly higher overall than dual users. Dual users rated “This product is a safer alternative to smoking” significantly higher than non-smokers. Messages did not differ on understandability. Conclusions These alternative messages provide a useful resource for future research and for policy makers considering updating e-cigarette product labelling.

Abstract Background E-cigarettes are the most popular aid to smoking cessation attempts in England and the USA. This research examined associations between e-cigarette device characteristics and patterns of use, tobacco-smoking relapse, and smoking abstinence. Methods A convenience sample of 371 participants with experience of vaping, and tobacco-smoking abstinence and/or relapse completed an online cross-sectional survey about e-cigarettes. Factors associated with smoking relapse were examined using multiple linear and logistic regression models. Results Most participants were self-reported long-term abstinent smokers (86.3%) intending to continue vaping. Most initiated e-cigarette use with a vape pen (45.8%) or cig-a-like (38.7%) before moving onto a tank device (89%). Due to missing data, managed through pairwise deletion, only around 70 participants were included in some of the main analyses. Those using a tank or vape pen appeared less likely to relapse than those using a cig-a-like (tank vs. cig-a-like OR = 0.06, 95% CI 0.01–0.64, p = 0.019). There was an inverse association between starting self-reported e-cigarette liquid nicotine concentration and relapse, interacting with device type (OR = 0.79, 95% CI 0.63–0.99, p = 0.047), suggesting that risk of relapse may have been greater if starting with a low e-cigarette liquid nicotine concentration and/or cig-a-like device. Participants reported moving from tobacco-flavored cig-a-likes to fruit/sweet/food flavors with tank devices. Conclusions Knowledge of how people have successfully maintained tobacco-smoking abstinence using vaping could help other tobacco smokers wishing to quit tobacco smoking through vaping.

Introduction: Many countries have now mandated warning labels on e-cigarette products. One example, the EU TPD health warning states, “This product contains nicotine which is a highly addictive substance. [It is not recommended for use by non-smokers]”. The impact of the EU TPD warning message on intentions to use, has not been explored within an EU population. Aims: Examine the effect of i) the TPD e-cigarette health warning and ii) an alternative relative risk message, on smokers' willingness to use, likelihood of purchase, and intention to use as a quit aid. Methods: Cross-sectional online study. Ninety-five smokers (55 males; 18–55 years old) were randomly allocated to one of three conditions and viewed ten individually presented e-cigarettes images with either no message, TPD message, or relative risk message. Participants rated i) willingness to use, and likelihood of: ii) purchase, iii) using in the next month, and iv) using in a quit attempt, before and after viewing the images. Results: For willingness to use and likelihood of purchase, ANCOVAs showed a significant main effect of Message Type (ps,

Background: Smoking prevalence is extremely high in adults experiencing homelessness, and there is little evidence regarding which cessation interventions work best. This study explored the feasibility of providing free electronic cigarette starter kits to smokers accessing homeless centres in the UK. Objectives: Seven key objectives were examined to inform a future trial: (1) assess willingness of smokers to participate in the study to estimate recruitment rates; (2) assess participant retention in the intervention and control arms; (3) examine the perceived value of the intervention, facilitators of and barriers to engagement, and influence of local context; (4) assess service providers’ capacity to support the study and the type of information and training required; (5) assess the potential efficacy of supplying free electronic cigarette starter kits; (6) explore the feasibility of collecting data on contacts with health-care services as an input to a main economic evaluation; and (7) estimate the cost of providing the intervention and usual care. Design: A prospective cohort four-centre pragmatic cluster feasibility study with embedded qualitative process evaluation. Setting: Four homeless centres. Two residential units in London, England. One day centre in Northampton, England. One day centre in Edinburgh, Scotland. Intervention: In the intervention arm, a single refillable electronic cigarette was provided together with e-liquid, which was provided once per week for 4 weeks (choice of three flavours: fruit, menthol or tobacco; two nicotine strengths: 12 or 18 mg/ml). There was written information on electronic cigarette use and support. In the usual-care arm, written information on quitting smoking (adapted from NHS Choices) and signposting to the local stop smoking service were provided. Results: Fifty-two per cent of eligible participants invited to take part in the study were successfully recruited (56% in the electronic cigarette arm; 50.5% in the usual-care arm; total n = 80). Retention rates were 75%, 63% and 59% at 4, 12 and 24 weeks, respectively. The qualitative component found that perceived value of the intervention was high. Barriers were participants’ personal difficulties and cannabis use. Facilitators were participants’ desire to change, free electronic cigarettes and social dynamics. Staff capacity to support the study was generally good. Carbon monoxide-validated sustained abstinence rates at 24 weeks were 6.25% (3/48) in the electronic cigarette arm compared with 0% (0/32) in the usual-care arm (intention to treat). Almost all participants present at follow-up visits completed measures needed for input into an economic evaluation, although information about staff time to support usual care could not be gathered. The cost of providing the electronic cigarette intervention was estimated at £114.42 per person. An estimated cost could not be calculated for usual care. Limitations: Clusters could not be fully randomised because of a lack of centre readiness. The originally specified recruitment target was not achieved and recruitment was particularly difficult in residential centres. Blinding was not possible for the measurement of outcomes. Staff time supporting usual care could not be collected. Conclusions: The study was associated with reasonable recruitment and retention rates and promising acceptability in the electronic cigarette arm. Data required for full cost-effectiveness evaluation in the electronic cigarette arm could be collected, but some data were not available in the usual-care arm. Future work: Future research should focus on several key issues to help design optimal studies and interventions with this population, including which types of centres the intervention works best in, how best to retain participants in the study, how to help staff to deliver the intervention, and how best to record staff treatment time given the demands on their time. Trial registration: Current Controlled Trials ISRCTN14140672; the protocol was registered as researchregistry4346. Funding: This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 9, No. 7. See the NIHR Journals Library website for further project information.

Background: Electronic cigarette regulations included in the Tobacco Products Directive (TPD), Article 20, implemented in Europe by May 2017, aimed to improve safety for e-cigarette consumers, and prevent uptake among non-smokers, particularly young people. Before implementation, there were significant concerns from consumers, industry, and some in the scientific community about the potential negative impact of the TPD on people using e-cigarettes to remain abstinent from smoking. To date, there is limited evidence on how the TPD has affected consumers. This study aimed to add insight into how consumers perceived and experienced the regulations. Methods: Qualitative data, collected between March 2018 and March 2019, relating to participant views of the TPD were extracted from 160 interviews/extended surveys of e-cigarette consumers as part of a wider study into e-cigarette use trajectories (ECtra study). Data were thematically analysed. Results: Awareness of the TPD among consumers was not universal. Participants’ smoking behaviour did not appear to be influenced by the legislation. Participants were reassured by manufacturing regulations and requirements for ingredients labels. Participants responded negatively to changes perceived to cause inconvenience and extra plastic waste. The product restrictions prompted some participants to purchase non-compliant products illegally, potentially putting their safety at risk. Conclusions: E-cigarette regulation should focus on ensuring product safety. Raising awareness of the TPD among consumers and smokers could be beneficial.

Smoking rates in the UK are at an all-time low but this masks considerable inequalities; prevalence amongst adults who are homeless remains four times higher than the national average. The objective of this trial was to assess the feasibility of supplying free e-cigarette starter kits to smokers accessing homeless centres and to estimate parameters to inform a possible future larger trial. In this feasibility cluster trial, four homeless centres in Great Britain were non-randomly allocated to either a Usual Care (UC) or E-Cigarette (EC) arm. Smokers attending the centres were recruited by staff. UC arm participants (N = 32) received advice to quit and signposting to the local Stop Smoking Service. EC arm participants (N = 48) received an EC starter kit and 4-weeks supply of e-liquid. Outcome measures were recruitment and retention rates, use of ECs, smoking cessation/reduction and completion of measures required for economic evaluation. Eighty (mean age 43 years; 65% male) of the 153 eligible participants who were invited to participate, were successfully recruited (52%) within a five-month period, and 47 (59%) of these were retained at 24 weeks. The EC intervention was well received with minimal negative effects and very few unintended consequences (e.g. lost, theft, adding illicit substances). In both study arm, depression and anxiety scores declined over the duration of the study. Substance dependence scores remained constant. Assuming those with missing follow up data were smoking, CO validated sustained abstinence at 24 weeks was 3/48 (6.25%) and 0/32 (0%) respectively for the EC and UC arms. Almost all participants present at follow-up visits completed data collection for healthcare service and health-related quality of life measures. Providing an e-cigarette starter kit to smokers experiencing homelessness was associated with reasonable recruitment and retention rates and promising evidence of effectiveness and cost-effectiveness.

Abstract Background Article 20 of the EU Tobacco Products Directive [TPD] stipulates that e-cigarette packets and refill products must carry a nicotine addiction health warning. Although previous studies conducted in North America have found that perceived harm, addictiveness and intention to use declined following exposure to e-cigarette health warnings, possible effects of the TPD health warnings on smokers and non-smokers has not been studied. This study will investigate the effects of the EU TPD e-cigarette health warnings and a comparative harm message (COMP; developed specifically for this study) on smokers’ and non-smokers’ perceptions of harm, addictiveness and social acceptability of e-cigarettes. Additionally, the potential effects of the TPD warnings and the COMP on smokers’ intentions to purchase and use e-cigarettes will be explored. Methods/design A sample of 2400 UK residents will be recruited in this experimental, randomised design, with Smoking status (Smoker vs. Non-smoker), TPD presence (TPD1 vs. TPD2 vs. No-TPD) and COMP presence (Presence vs. Absence) as between subjects independent variables, and Time (pre-post exposure of images) as a within subjects factor. Dependent variables comprise self-reported perceived harm, addictiveness, social acceptability, e-cigarettes’ effectiveness, intentions to purchase and use e-cigarettes. Cigarette dependence, previous e-cigarette exposure, and baseline intentions to quit will be measured as covariates. Discussion Health warnings, such as those implemented by the TPD, may help to prevent non-smokers from e-cigarettes use, but it is possible that they may inadvertently deter smokers from initiating use and substituting their tobacco smoking for e-cigarettes use if their content is deemed too negative. It is hoped that this study will help identify the most effective message or combination of messages that encourage use among smokers without promoting use among non-smokers. Trial registration ISRCTN registry ISRCTN76967031; date of registration: 23/10/18.

E-cigarettes (EC) are now the most popular quit aid in England but their effectiveness for cessation if offered at a pharmacy has not been tested. Here we test the effectiveness of offering an e-cigarette with and without nicotine replacement therapy (NRT) on 4–6-week quit rates in adult smokers seeking support from a community pharmacy. A between subject, six-week, prospective, cohort design. 115 smokers (female = 74; M age = 46.37, SD = 13.56) chose either an EC, EC + NRT or NRT alone, alongside standard behavioural support. Smokers opting for an EC alone or an EC + NRT were more likely to report complete abstinence from smoking at 4–6 weeks (62.2% and 61.5% respectively) compared to NRT alone (34.8%). An EC intervention was significantly more effective for smoking cessation than NRT in this community pharmacy. The results for e-cigarettes appear positive but with the caveat that participants chose their own products which may have introduced bias. Keywords: E-cigarettes, Smoking cessation, Pharmacy, Nicotine replacement therapy

Abstract Background We have little understanding of how vapers use e-cigarettes beyond cessation. E-cigarettes may have a role to play in reducing the health-related harms of tobacco smoking, through not only assisting smoking cessation attempts but also supporting long-term abstinence from smoking. However, there are fears that vaping may lead to the ‘renormalisation’ of smoking type behaviours. This study aimed to explore patterns of use and reported experiences of vapers quitting smoking using an e-cigarette in relation to long-term smoking status (abstinence or relapse). Methods A purposive sample of 40 UK vapers was matched to a sampling frame of demographic characteristics from a representative sample of UK quitters. Following full informed consent, semi-structured qualitative interviews were conducted. Data were thematically analysed by two members of the research team. Final thematic analysis was verified and agreed by consensus. Results The sample self-reported long histories of tobacco use and multiple previous quit attempts which had eventually resulted in relapse back to smoking, although a small but important group had never before attempted to quit. Initiating e-cigarette use was experienced as a revelation for some, who were quickly able to fully switch to using e-cigarettes as an alternative to tobacco smoking. For others, periods of dual use or smoking relapse combined with attempts at vaping that were not initially satisfactory. Many of these chose a cheaper ‘cig-a-like’ device which they found to be inadequate. Experimentation with different devices and different setups, over time, resulted in some ‘sliding’ rather than switching to vaping. This involved periods of ‘dual use’. Some settled on patterns of vaping as a direct substitute of previous tobacco smoking, whereas others reported ‘grazing’ patterns of vaping throughout the day that were perceived to support tobacco smoking abstinence. Conclusions Our data demonstrates that e-cigarettes may be a unique harm reduction innovation for smoking relapse prevention. E-cigarettes meet the needs of some ex-smokers by substituting physical, psychological, social, cultural and identity-related aspects of tobacco addiction. Some vapers reported that they found vaping pleasurable and enjoyable—being more than a substitute but actually preferred, over time, to tobacco smoking. This clearly suggests that vaping is a viable long-term substitute for smoking, with substantial implications for tobacco harm reduction.

Background: Over the past few years, a large number of smokers in the UK have stopped smoking with the help of e-cigarettes. So far, UK Stop Smoking Services (SSSs) have been reluctant to include e-cigarettes among their treatment options because data on their efficacy compared with the licensed medications are lacking. Objective: The objective was to compare the efficacy of refillable e-cigarettes and nicotine replacement therapy (NRT) products, when accompanied by weekly behavioural support. Design: A randomised controlled trial comparing e-cigarettes and NRT. Setting: Three sites that provide local SSSs. Participants: The participants were 886 smokers seeking help to quit smoking, aged ≥ 18 years, not pregnant or breastfeeding, with no strong preference to use or not to use NRT or e-cigarettes in their quit attempt, and currently not using NRT or e-cigarettes. A total of 886 participants were randomised but two died during the study (one in each study arm) and were not included in the analysis. Interventions: The NRT arm (n = 446) received NRT of their choice (single or combination), provided for up to 12 weeks. The e-cigarette arm (n = 438) received an e-cigarette starter pack and were encouraged to buy addtional e-liquids and e-cigarette products of their choice. Both arms received the same standard behavioural support. Participants attended weekly sessions at their SSS and provided outcome data at 4 weeks. They were then followed up by telephone at 6 and 12 months. Participants reporting abstinence or at least 50% reduction in cigarette consumption at 12 months were invited to attend for carbon monoxide (CO) validation. Participants/researchers could not be blinded to the intervention. Main outcome measures: The primary outcome was CO-validated sustained abstinence rates at 52 weeks. Participants lost to follow-up or not providing biochemical validation were included as non-abstainers. Secondary outcomes included abstinence at other time points, reduction in smoke intake, treatment adherence and ratings, elicited adverse reactions, and changes in self-reported respiratory health. A cost-efficacy analysis of the intervention was also conducted. Results: The 1-year quit rate was 9.9% in the NRT arm and 18.0% in the e-cigarette arm (risk ratio 1.83, 95% confidence interval 1.30 to 2.58; p

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

Abstract Background Contrary to intuition, use of lower strength nicotine e-liquids might not offer reduced health risk if compensatory puffing behaviour occurs. Compensatory puffing (e.g. more frequent, longer puffs) or user behaviour (increasing the wattage) can lead to higher temperatures at which glycerine and propylene glycol (solvents used in e-liquids) undergo decomposition to carbonyl compounds, including the carcinogens formaldehyde and acetaldehyde. This study aims to document puffing patterns and user behaviour associated with using high and low strength nicotine e-liquid and associated toxicant/carcinogen exposure in experienced e-cigarette users (known as vapers herein). Methods/design A counterbalanced repeated measures design. Participants: Non-tobacco smoking vapers; have used an e-cigarette for ≥3 months; currently using nicotine strength e-liquid ≥12mg/mL and a second or third generation device. Intervention: This study will measure puffing patterns in vapers whilst they use high and low strength nicotine e-liquid under fixed and user-defined settings, each for a week. The 4 counterbalanced conditions are: i) low strength (6mg/mL), fixed settings; ii) low strength user-defined settings; iii) high strength (18mg/mL) fixed settings; iv) high strength user-defined settings. Biomarkers of exposure to toxicants and carcinogens will be measured in urine. In the second phase of this study, toxicant yields will be measured in aerosol generated using a smoking machine operated to replicate the puffing behaviours of each participant. Primary outcomes: i) Puffing patterns (mean puff number, puff duration, inter-puff interval and mL of liquid consumed) and user behaviour (changes to device settings: voltage and air-flow) associated with using high and low strength nicotine e-liquid. ii) Toxicant/carcinogen exposure associated with the puffing patterns/device settings used by our participants. Secondary outcomes: i) Subjective effects. ii) comparisons with toxicant exposure from tobacco smoke (using documented evidence) and with recommended safety limits. Sample size: Twenty participants. Discussion The findings will have important implications for public health messaging regarding the relative risks and subjective effects associated with using high and low strength nicotine e-liquid, and for policy makers regarding regulations on nicotine concentrations in e-liquids.

After publication of the original article [1], the authors noticed an error in the Competing interests section.