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Exploring the opinions and potential impact of unflavoured e-liquid on smoking cessation among people who smoke and smoking relapse among people who previously smoked and now use e-cigarettes: findings from a UK-based mixed methods study

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Background Although electronic cigarettes (e-cigarettes) appear to be effective in helping people who smoke to stop smoking, concerns about use of e-cigarettes among young people have led to restrictions on non-tobacco flavoured e-liquids in some countries and some US states. These restrictions could reduce the appeal of these products to non-smoking youth but could have negative consequences for people who smoke or use e-cigarettes. Methods In this mixed methods study, we recruited UK adults who smoked or used to smoke and subsequently vaped to explore their opinions of unflavoured e-liquids and their beliefs about how they would be impacted by hypothetical e-liquid flavour restrictions. Participants trialled an unflavoured e-liquid instead of their usual nicotine product for four hours and completed a survey and an online interview. Results Using Interpretive Phenomenological Analysis and graphically presented data, we found differences in participants’ opinions of unflavoured e-liquid. If only unflavoured, tobacco flavoured, and menthol flavoured e-liquids remained on the UK market, some people who smoke or vape may be unaffected, but some may relapse to smoking or continue smoking. Despite most wanting to prevent young people from initiating vaping, participants had varying opinions on whether flavour restrictions would be an effective method. Conclusions The findings highlight that people who smoke and vape could be impacted by flavour restrictions in a range of ways, some of which could have a potential adverse impact on harm reduction efforts in the UK (e.g., by making smoking more appealing than vaping).
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Khoujaetal. Harm Reduction Journal (2024) 21:90
https://doi.org/10.1186/s12954-024-01003-z
RESEARCH
Exploring theopinions andpotential impact
ofunavoured e-liquid onsmoking cessation
amongpeople who smoke andsmoking relapse
amongpeople who previously smoked andnow
use e-cigarettes: ndings fromaUK-based
mixed methods study
Jasmine N. Khouja1,2*, Maddy L. Dyer1,2, Michelle A. Havill3, Martin J. Dockrell3, Marcus R. Munafò1,2,4 and
Angela S. Attwood1,2
Abstract
Background Although electronic cigarettes (e-cigarettes) appear to be effective in helping people who smoke
to stop smoking, concerns about use of e-cigarettes among young people have led to restrictions on non-tobacco
flavoured e-liquids in some countries and some US states. These restrictions could reduce the appeal of these prod-
ucts to non-smoking youth but could have negative consequences for people who smoke or use e-cigarettes.
Methods In this mixed methods study, we recruited UK adults who smoked or used to smoke and subsequently
vaped to explore their opinions of unflavoured e-liquids and their beliefs about how they would be impacted
by hypothetical e-liquid flavour restrictions. Participants trialled an unflavoured e-liquid instead of their usual nicotine
product for four hours and completed a survey and an online interview.
Results Using Interpretive Phenomenological Analysis and graphically presented data, we found differences in par-
ticipants’ opinions of unflavoured e-liquid. If only unflavoured, tobacco flavoured, and menthol flavoured e-liquids
remained on the UK market, some people who smoke or vape may be unaffected, but some may relapse to smoking
or continue smoking. Despite most wanting to prevent young people from initiating vaping, participants had varying
opinions on whether flavour restrictions would be an effective method.
Conclusions The findings highlight that people who smoke and vape could be impacted by flavour restrictions
in a range of ways, some of which could have a potential adverse impact on harm reduction efforts in the UK (e.g.,
by making smoking more appealing than vaping).
Keywords e-cigarette, Vaping, Smoking, e-liquid flavour, Flavour restriction, Flavour ban, Gateway hypothesis
Open Access
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Harm Reduction Journal
*Correspondence:
Jasmine N. Khouja
jasmine.khouja@bristol.ac.uk
Full list of author information is available at the end of the article
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Page 2 of 16
Khoujaetal. Harm Reduction Journal (2024) 21:90
Background
Electronic cigarettes (also known as e-cigarettes or
vapes) are battery-operated devices that heat a liquid
(also known as e-liquid) to create an aerosol, which can
be inhaled. Using e-cigarettes is sometimes referred to
as ‘vaping’ [33]. With approximately 4.7 million people
who vape in Great Britain, many people use e-cigarettes
to cut down or stop smoking [4]. A living systematic
review of e-cigarette use for smoking cessation suggests
that e-cigarettes are an effective smoking cessation aid
[31]. e efficacy of e-cigarettes as smoking cessation
tools may be partly dependent on the array of flavours
available to aid or maintain smoking reduction or ces-
sation [23], but some countries and US states have poli-
cies restricting e-liquid flavour availability. At a federal
level, the USA only permits tobacco and menthol fla-
vours in certain products, but in some US states this
flavour ban applies to all e-cigarette products, and Fin-
land only permits tobacco flavours. In January 2024, the
UK government announced they will be introducing
new powers to restrict flavours in e-cigarettes. Given
that e-cigarettes have the potential to reduce harm at
a population-level, it is important to understand the
impact that restrictions may have on people who smoke
and people who have quit smoking and switched to
vaping in the UK.
E-liquid restrictions have been implemented in some
countries and US states due to the belief that flavoured
e-liquids appeal to non-smoking youth [47]. It has been
suggested that e-cigarettes may attract youth who have
never smoked, and that using e-cigarettes could lead
to smoking initiation, commonly known as the “gate-
way effect” [14]. Research has found a strong positive
association between e-cigarette use and later smoking
among individuals who have not smoked prior to using
e-cigarettes [5]. However, evidence from time-series
analyses in England have not supported this theory
[6] and the association could be due to the two behav-
iours sharing a common liability, for example a propen-
sity to risk-taking [28]. Nevertheless, these concerns
have led to e-liquid flavour restrictions in some coun-
tries and US states, and similar restrictions have been
announced in the UK. is is despite little being known
about the potential negative unintended public health
consequences of such restrictions for UK adults who
smoke or previously smoked and now vape.
Restrictions on the sale of flavoured e-liquids could
result in people who transitioned from smoking to vap-
ing returning to smoking (i.e., relapsing). Just under
one in five people who use e-cigarettes surveyed in
Great Britain stated that they would smoke more or
revert to smoking if flavours were no longer available
[3]. People who smoke may also be less interested in
using e-cigarettes to stop smoking without the avail-
ability of a range of flavours.
If the number of adults who return to smoking or
decide not to stop smoking using an e-cigarette out-
weighs the number of young people who are protected
from vaping (and potentially subsequent smoking), then
restrictions of e-liquid flavours could result in a net
increase in the number of people who smoke in the pop-
ulation [24]. Current evidence suggests that cigarettes
pose a much greater health risk than e-cigarettes [34], so
the number of young people protected may need to sub-
stantially outweigh the number of people who return to
or continue smoking cigarettes, to result in a net decrease
in population harm. Alternatively, if people who smoke
or vape positively perceive e-liquids which would remain
on the market in the event of a flavour restriction (e.g.,
unflavoured e-liquid), then the overall impact of e-liq-
uid flavour restrictions on people who smoke or used to
smoke and now vape could be negligible. If they believe
that flavour restrictions would have little impact on their
behaviour (i.e., they would be just as likely to attempt to
stop smoking and would be no more likely to return to
smoking) then flavour restrictions could result in fewer
people smoking in the population. Although unflavoured
e-liquids (i.e., e-liquids containing propylene glycol, veg-
etable glycerin and nicotine without flavourings) would
be available if these hypothetical restrictions were imple-
mented, only 1.4% of adults who vaped in the UK in 2023
reported using unflavoured products [4], so some people
who vape or smoke in the UK could be undecided about
unflavoured e-liquid.
Understanding the opinions of people who smoke or
previously smoked and now vape about unflavoured
e-liquids could inform policies. It is also important to
understand how people who smoke or previously smoked
and now vape believe their future e-cigarette use, smok-
ing behaviours, and behavioural intentions may be
impacted by e-liquid flavour restrictions (e.g., banning all
e-liquid flavourings except menthol and tobacco). ere
have been few qualitative explorations of the impact of
e-liquid flavour bans or restrictions. One study focused
on young US adults who smoked and vaped, finding that
banning or restricting flavours (aside from tobacco, men-
thol or unflavoured e-liquids) could discourage them
[15]. Another study among young adults in China who
vaped daily for at least three months found they had used
a range of adaptative strategies in the 1–3months since
[52]. ese strategies included sourcing illegal products
and using custom-made cartridge covers which added
flavours to add flavours to legal products. After a restric-
tion on flavoured cartridge-based vaping products in
the US, young adults reported stockpiling, buying ille-
gal products online, switching to legal flavours, and
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Page 3 of 16
Khoujaetal. Harm Reduction Journal (2024) 21:90
reducing use, but stated they might stop vaping, switch
to cigarettes, or stockpile if flavours were comprehen-
sively restricted in all vaping products [41]. ese results
cannot be generalised to adults who smoke or vape in
other countries with different regulations, available prod-
ucts, and societal contexts. Among i) adults who cur-
rently smoke and ii) adults who currently vape (who have
stopped smoking within the last 12months) in the UK,
we aimed to explore: 1) their opinions of unflavoured
e-liquid after a brief trial (4h) of an unflavoured e-liquid,
and 2) how participants believe a hypothetical e-liquid
flavour restriction (i.e., banning non-tobacco and non-
menthol flavoured e-liquids) may impact their future
smoking behaviour, vaping, and future intentions to vape
unflavoured e-liquids.
Methods
Design
is exploratory observational study using mixed meth-
ods followed the methods outlined in our online pre-
registered study protocol (https:// osf. io/ snmp9), except
where specified. Ethics approval was obtained from the
University of Bristol School of Psychological Science
Human Research Ethics Committee, a subcommittee of
the Faculty of Life Sciences Ethics Committee (reference:
010421116008).
Participants
We recruited 24 healthy UK residents between April
2021 and July 2021—12 adults who smoked daily and 12
adults who vaped daily (who stopped smoking within the
12months prior to the study session) as daily vaping is
strongly associated with smoking cessation and daily
smoking is associated with using a quit aid in a smoking
cessation attempt [25, 48]. We recruited four people who
smoked 20 or more cigarettes per day (CPD) and two
people who vaped daily but used to smoke 20 or more
CPD (two fewer than stated in our preregistered proto-
col due to difficulties in recruitment). A previous quali-
tative study exploring perceptions of e-liquid flavours
among young adults who both smoked and vaped in the
US included 25 interviews [15], therefore, we anticipated
that 24 interviews would be sufficient to achieve satura-
tion of themes [50]. Participants were recruited through
existing email lists, social media (Facebook and Twitter
adverts), word of mouth, and via the University of Bristol
Tobacco and Alcohol Research Group (TARG) newsletter
and website.
Participants were 18 years of age or older, fluent in
English, and they self-identified as either a person who
smoked daily or a person who vaped daily. Daily smok-
ing was defined as currently smoking five or more times
per day for three months or more. Participants who
smoked were not currently attempting to stop smoking
(i.e., not currently using nicotine replacement products
or in active smoking cessation treatment) and were not
currently vaping. Daily vaping was defined as currently
using a nicotine-containing e-cigarette five or more
times per day for three months or more. Participants
who vaped daily and previously smoked had recently
stopped smoking. is was defined as having previously
met the criterion of currently smoking in the 12months
before the study and having replaced smoking with use
of an e-cigarette for at least one month before the study.
From here on, we refer to these participants as “partici-
pants who vaped”. Participants who vaped were required
to currently only be using non-tobacco and non-menthol
flavoured e-liquids (e.g., fruit flavoured e-liquids). Full
eligibility criteria are listed in Additional file1 (Sect.1.1).
All eligibility criteria were assessed via self-report, and
nicotine use and pregnancy criteria were verified using
self-administered urine tests. Presence of cotinine in
urine, a highly specific biomarker for nicotine [7], was
used to confirm current nicotine use.
Measures andmaterials
E‑cigarette ande‑liquid
Participants received an Arc 5 starter kit purchased
from Totally Wicked (https:// www. total lywic ked- eliqu
id. co. uk/ arc-5). Each kit contained one e-cigarette with
a 2200mAh internal battery, a CS Air Slim tank, and an
atomizer head, a USB charging cable, and a user man-
ual. A tank-style device was selected as it was the most
popular device type among adults who regularly vape in
Great Britain at the time of the study [3]. Each partici-
pant received one 10ml bottle of unflavoured Red Label
e-liquid (50:50 PG/VG) (https:// www. total lywic ked- eliqu
id. co. uk/ unfla voured- red- label. e e-liquid contained
one of two nicotine concentrations (10mg/ml or 18mg/
ml that best reflected a participant’s typical nicotine use
(based on CPD or usual e-liquid nicotine concentration;
Additional file1, Sect.1.2).
Measures
Age, gender, ethnicity, and where applicable, frequency
and duration of current and/or past smoking, frequency
and duration of current and/or past e-cigarette use, and
time since smoking cessation were recorded in a Qual-
trics survey [40] (Additional file 2: Tables S1 and S2).
Descriptive quantitative data on participant character-
istics and perceptions of unflavoured e-liquids prior to
exposure were collected. Items measured participants’
willingness and intentions to use unflavoured e-liquids if
flavoured e-liquids (i.e., non-tobacco, non-menthol fla-
voured) were restricted. Participants who smoked were
asked if they would be willing to attempt to stop smoking
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Page 4 of 16
Khoujaetal. Harm Reduction Journal (2024) 21:90
using an e-cigarette, and with unflavoured e-liquid. Moti-
vation to quit smoking was measured using the readiness
to quit ladder [1]. e readiness to quit ladder ranges
from 1 (“I have decided not to quit smoking for my life-
time. I have no interest in quitting”) to 10 (“I have quit
smoking”). Participants who vaped were asked to report
how many times per day they used their e-cigarette and
were advised to assume that one ‘time’ lasts for around
10min or consists of around 15 puffs [21]. Participants
who vaped were asked: (a) if they believed they would
have quit smoking using an e-cigarette if they had used
an unflavoured e-liquid, (b) if they thought they would
switch to using an unflavoured e-liquid if flavours were
restricted, and (c) if they thought they would relapse
to smoking instead of switching from a flavoured to an
unflavoured e-liquid if e-liquid flavours were restricted.
ey were then asked what they would do if flavoured
e-liquids were removed from the market (e.g., no sweet
or fruit flavours), and only tobacco, menthol/mint and
unflavoured e-liquids were available. ey could select
multiple answers from the options provided, and/or
insert another answer. ese questions and response
options are described in full in Additional file2: Tables
S1 and S2.
Interview
e semi-structured interview included open-ended
questions that were intended to encourage the partici-
pants to discuss: (1) their experience and opinions of
using unflavoured e-liquid, and (2) how they perceived
a restriction on e-liquid flavours may impact their future
smoking behaviour, vaping, and future intentions to vape
unflavoured e-liquids. Specifically, participants were
asked to consider a proposed scenario in which “fla-
voured e-liquids were removed from the market, and
only unflavoured, tobacco or menthol/mint flavours
were available”. We additionally asked about their previ-
ous experiences with smoking and vaping, and their gen-
eral thoughts on the hypothetical proposed restrictions.
e full interview schedule (including topic guide) is
included in Additional file2: Tables S3 [for people who
smoked] and S4 [for people who vaped]). e topic guide
was developed based on existing literature [12, 54] and
known evidence gaps (detailed in the introduction).
Procedures
Potential participants self-reported their eligibility to
participate during a telephone screening and com-
pleted an online written consent form via Qualtrics.
Participants provided a postal address. is first session
lasted ~ 20min. Following the telephone screening, the
researcher posted an e-cigarette starter kit, objective
screening tests (for cotinine and pregnancy, if female),
instructions, a cleaning wipe (for the device), and a cover
letter to the participant via Royal Mail. e e-cigarette
voltage was set to 12W, but participants were instructed
to modify this if desired.
Approximately one week later, on the morning of their
test session day, the participant completed the objec-
tive screening measures (a cotinine test and if female, a
pregnancy test). ese screening sessions were via video
call [55] and were scheduled between 8 am and 1 pm
on the same day of the urine test(s). In the final screen-
ing session, the participant showed their cotinine (and if
applicable, pregnancy) test results to the researcher on
camera. Eligible participants were sent a link to an online
Qualtrics survey via email to progress to Session 1 of the
study. e survey assessed participant characteristics and
participants’ perceptions of unflavoured e-liquids and
e-liquid flavour restrictions. Following survey comple-
tion, the researcher instructed the participant to set up
their e-cigarette, fill it with the e-liquid provided, and use
this device instead of smoking or using their usual vap-
ing products until Session 2 (~ 4h later). Final screen-
ing and Session 1 were completed during one video call
lasting ~ 20min.
In Session 2, participants reported their puff count
(recorded by the e-cigarette), provided verbal consent
to begin the audio recording of the interview, and com-
pleted a semi-structured interview via a video call [55].
After the interview, participants were emailed a debrief
sheet and a voucher for participation (worth £20). Inter-
views usually lasted 15–25 min and were transcribed
verbatim.
Analyses andinterpretation
We report all quantitative data for participants who
smoked and participants who vaped separately due to
differences in the survey questions. In contrast to our
pre-registered protocol, we have not graphically pre-
sented the interview responses regarding predicted
behaviour in response to flavour restrictions, intentions,
and willingness to vape or use unflavoured e-liquids, as
the responses were ambiguous in many cases, making
quantification imprecise.
We used Interpretative Phenomenological Analysis
(IPA) to analyse the qualitative data. IPA is a method-
ology in which the analyst takes an active role in inter-
preting how participants make sense of their social and
personal world [45]. e most common IPA approach
is to use transcripts from semi-structured interviews to
identify common themes to explore the personal percep-
tions or accounts of an event [46]. In this analysis, two
researchers analysed 50% of the data each by transcrib-
ing the recordings, reading the transcriptions, and mak-
ing notes (i.e., coding the transcript). is process was
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Khoujaetal. Harm Reduction Journal (2024) 21:90
repeated by a third researcher who resolved any disa-
greements about codes between the other researchers.
e third researcher then compiled emerging themes by
condensing the related notes into concise phrases which
referred to a higher-level concept. e themes were then
clustered into superordinate and subthemes by identi-
fying conceptual similarities between them. Finally, we
reviewed the themes in relation to the transcript notes
to check that they suitably reflected the notes and were
named appropriately.
Results
Participant characteristics andbaseline data
Participants who smoked and participants who vaped
were similar in age (ranging from 19 to 62years), gen-
der, ethnicity, number of cigarettes smoked (currently or
in the past) and smoking history (Table1). Participants
who vaped reported using a range of e-liquid nicotine
strengths (some reported using more than one), but all
participants used less than 19 mg/ml (in line with UK
regulations). All participants used fruit flavoured e-liq-
uids, but some participants also reported using other
flavours (either in the survey or during the interview)
such as “pastry flavours”. Responses to this questionnaire
item, such as "various berry flavours”, limited our ability
to determine how many flavours or which specific fla-
vours were used by each participant (Additional file 2:
TableS5). Participants reported the average puff count
(84 for participants who smoked and 83 for participants
who vaped) and duration (8 min, 56s for participants
who smoked and 7min, 23s for participants who vaped)
displayed on the e-cigarette device. Frequency of e-ciga-
rette use can be difficult for people who vape to estimate
[21] and at least one participant reported the number of
puffs they took per day instead of the number of times
they vaped per day.
Baseline quantitative data regarding predicted behav-
iour in response to flavour restrictions, intentions, and
willingness to vape or use unflavoured e-liquids are pre-
sented in Figs.1, 2, 3.
Themes
We identified six superordinate themes through IPA
(Table2). e ‘intentions and motivations to stop smok-
ing and/or use e-cigarettes’ theme provides insights into
the participants’ past and/or future likelihood of smoking
and vaping irrespective of a flavour restriction. As this
provides context but does not answer our research ques-
tion, it can be found in Additional file1, Sect.2.1. Other
superordinate themes are discussed below except for sub-
themes which were infrequently raised or ambiguously
linked to the superordinate theme ‘other drivers of vaping
behaviour are more important than flavours’ (Additional
file1, Sect. 2.2). For clarity, we indicate which partici-
pants vape and which smoke with a ‘V’ or ‘S’, respectively,
at the end of their participant number.
Sensations andexperience ofusing unavoured e‑liquid
In this theme, participants described the ‘sensations
and experience of using unflavoured e-liquid’. Par-
ticipants often described their experience of using the
unflavoured e-liquid in terms of the harshness and
throat hit, with people who vaped usually describing a
Table 1 Participant characteristics and survey responses relating
to a hypothetical flavour restriction
Responses recorded prior to a 4-h trial of unavoured e-liquid. Only the options
selected by participants are displayed in the table. Some questions were not
asked to either people who vaped or people who smoked in the Qualtrics
survey; a dash (-) indicates this question was not asked. The readiness to quit
ladder ranges from 1 (I have decided not to quit smoking for my lifetime, I have
no interest in quitting) to 10 (I have quit smoking) [1]. *Cigarettes smoked per
day prior to stopping smoking
Variable Participants who
vaped (N = 12)
N (%)
Participants who
smoked (N = 12)
N (%)
Female gender 7 (58%) 7 (58%)
Male gender 5 (42%) 5 (42%)
Black/African/Caribbean/Black
British Ethnic group 0 (0%) 1 (8%)
White Ethnic group 12 (100%) 11 (92%)
Smoked daily for 6–12 months 1 (8%) 0 (0%)
Smoked daily for 1–2 years 1 (8%) 4 (33%)
Smoked daily for 2–5 years 1 (8%) 3 (25%)
Smoked daily for 5 + years 9 (75%) 5 (42%)
Wants to quit smoking
Yes 1 (8%)
Maybe 9 (75%)
No 2 (17%)
Ever vaped 12 (100%) 8 (67%)
Vaped for 3–6 months 6 (50%)
Vaped for 6–12 months 5 (42%)
Vaped for 1–2 years 1 (8%)
Nicotine strength: 1–3 mg/ml 3 (25%)
Nicotine strength: 4–6 mg/ml 2 (17%)
Nicotine strength: 7–9 mg/ml 2 (17%)
Nicotine strength: 10–12 mg/ml 3 (25%)
Nicotine strength: 13–15 mg/ml 1 (8%)
Nicotine strength: 15–18 mg/ml 1 (8%)
E-liquid flavour used (fruit) 12 (100%)
E-liquid flavour used (other) 2 (17%)
Mean (SD) Mean (SD)
Age (years) 31 (11) 27 (12)
Cigarettes smoked per day 13 (5)* 13 (6)
Readiness to quit score 4 (2)
Times vaped per day 24 (17)
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Khoujaetal. Harm Reduction Journal (2024) 21:90
harsher experience than their usual product and people
who smoked describing a lesser throat hit compared to
smoking. P015V said “I thought it felt quite harsh” and
P020V stated, “it was just like nothing, except like just the
harsh feeling of the smoke itself.” In contrast, P025S said,
“ere was no coughing or that harshness which is some-
thing you have when you have a cigarette” and P022S said
“it didn’t really give that hit on the erm… throat that the
cigarettes normally give you.
e majority of participants who smoked thought
the unflavoured e-liquid satisfied their cravings for
cigarettes or nicotine but for others, it did not satisfy
other elements of cigarette enjoyment. P001S said, “it
gave me nicotine, and like I didn’t crave a smoke at
all” and P012S said, “it definitely eliminated my crav-
ings for cigarettes because I was constantly reaching
for [the e-cigarette].” P021S said “I’d definitely say it
hit the […] nicotine craving, but probably not the sort
01234567
Other
Don't know
Stop vaping
Start smoking
Use tobacco flavoured e-liquid
Use unflavoured e-liquid
Use menthol flavoured e-liquid
Make own flavours
Use illegal flavours
Number of Responses
Fig. 1 Actions that people who previously smoked and subsequently vaped would take if there was an e-liquid flavour restriction (N = 12).
Participants responded to multiple choice questions relating to a hypothetical flavour restriction in which only unflavoured, tobacco flavoured,
and menthol flavoured e-liquids remained on the market (recorded at baseline)
0
1
2
3
4
5
6
7
YesMaybe No
Number of Responses
Fig. 2 Perceived success of participants who used a vape to stop smoking if they had used unflavoured e-liquid to stop smoking instead (N = 12).
Participants responded to the question: "If you had used an unflavoured e-liquid when you quit smoking, do you think you would have successfully
quit?" (recorded at baseline)
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Khoujaetal. Harm Reduction Journal (2024) 21:90
of unconscious pleasure I get from sort of having a
cigarette compared to a vape.” P002S thought that the
remaining craving was for the “ritual of smoking as
opposed to like just the nicotine side of it.” Some par-
ticipants who vaped also stated that the unflavoured
e-liquid satisfied their cravings for nicotine, but they
did not enjoy the experience. When P014V was asked
“did you enjoy using it?”, they responded, “I kind of did
in a way, because […] it’s satisfying a craving, the crav-
ing for nicotine, […] but the thing that I disliked really
was the fact that it’s unflavoured”. P009V said the unfla-
voured e-liquid “quelled the, the want for […] nicotine
generally, but I, I didn’t enjoy the experience, which I
would normally with the flavoured stuff.
Some participants commented on the similarities
between smoking and using the unflavoured e-liquid.
Most participants who smoked made general compari-
sons about vaping which were not specific to the unfla-
voured e-liquids, but P022S stated, “in terms of taste
I cannot say that I’ve seen any noticeable difference
[between using unflavoured e-liquid and smoking], which
is good because it can serve as a replacement.” P002S said
“I’ve tried the tobacco [e-liquids] and they’re not, they’re
not quite like tobacco […] there’s more of a resemblance
in the unflavoured one.” P020V was less positive about
the similarity and said, “obviously it is unflavoured, and
it, it didn’t have a flavour, but at the same time, it did, in
the sense of, it’s just, it was just harsh, and dry […] like
smoking”. P023S said, “I know it’s designed to simulate
tobacco, which it does sort of an alright job of, but it’s
basically the same but slightly more horrible.
Participants generally had no expectations or nega-
tive expectations prior to using the unflavoured e-liquid.
Where participants had no expectations, it was usually
because they had not heard of unflavoured e-liquids.
P015V stated, “I didn’t actually know they existed, I
thought it was just tobacco, menthol and the other fla-
vours”, and “I didn’t really have an opinion I just thought,
‘this is going to be horrible’”. Among those who had
negative opinions prior to using the unflavoured e-liq-
uid, some were pleasantly surprised; P014V said, “I felt
like I was gonna be ripping me hair out for four hours,
[because] I haven’t got my normal berry vape with me,
but it wasn’t actually that bad really”. Others had their
negative expectations confirmed, like P017V: “I expected
it to be pretty bad, and it was pretty bad” and “it can’t
even stand in the shadow of what I normally vape.” Par-
ticipants who smoked tended not to have strong expec-
tations about the unflavoured e-liquid prior to trying it,
but some were positive after. For example, P003S admit-
ted “I didn’t think I was going to enjoy it, and I didn’t
see the point in having an unflavoured one, but actually
[…] I didn’t mind it and it was, it was quite nice.” P021S
said, “unflavoured liquid would be the way I would go if
I decided to take up vaping in the future”. Some partici-
pants who smoked were ambivalent after trying unfla-
voured e-liquids. P011S shared, “I thought it was going
to taste worse than it did. […] I didn’t have any like ‘wow
this is amazing’ either.” Some participants who smoked
had negative opinions of the unflavoured e-liquid, like
P023S who described it as “a flavour that you’d rather not
have”.
024681012
Willingness to vape unflavoured e-liquid
Willingness to vape unflavoured e-liquid to stop smoking
if flavours were restricted
Intentions to vape in the future to stop smoking
Intentions to use an unflavoured e-liquid in the future to
stop smoking
Participants who smoked
Willingness to vape unflavoured e-liquid
Intentions to vape unflavoured e-liquid in the future
Participants who vaped
Number of Responses
Yes MaybeNo
Fig. 3 Participants’ willingness and intentions to vape or vape unflavoured e-liquid. Response options were “Yes” or ‘No”, with no “Maybe” option
in the survey for participants who used to smoke and subsequently vaped. Responses were recorded at baseline
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Khoujaetal. Harm Reduction Journal (2024) 21:90
ere were mixed opinions among participants who
vaped. P004V and P006V found it “worse” than they
expected and P020V’s ambivalent opinion changed to
it being “vile” after trying the e-liquid. P020V said, “you
might as well just not have anything or […] not quit
smoking.” P017V said “unflavoured’s pretty grim” and “it’s
like having unflavoured toast, you’re not just gonna have
like a bit of toast in the morning with nothing on it, are
you? Like you probably could, you wouldn’t enjoy it, but,
if you can, chuck a bit of flavour on there.” P019V said
“It’s like drinking water instead of squash” and “I’m not
sure I would choose the unflavoured again” because they
preferred “fruity.” Some participants who vaped were
more positive, for example P013V said, “I wouldn’t of
chose it, but […] it’s alright” and “I would definitely use it
again”. Some participants who vaped were not overly pos-
itive but said they “could probably get used to it” (P016V)
or “could probably firm it out and get used to it after a
week or two but I wouldn’t enjoy myself for that week”
(P017V).
Some participants who vaped commented on the use
of unflavoured e-liquids to stop vaping or using nicotine
products entirely. If P006V were using e-cigarettes to
“withdraw from nicotine completely then […] I could see
like a chemist giving [unflavoured e-liquid] out for exam-
ple, because there’s not much enjoyment to it.” P015V
said, “I’d say it’s quite likely [I would use unflavoured
e-liquid again] because I don’t think I’m ever gonna get
off vaping completely if I’m having things that are really
nice” and P009V said “if I wanted to stop vaping maybe I
should stop making it taste like Eton mess [a dessert con-
taining cream, meringue and fruit.]” P020V said unfla-
voured e-liquid “is a good way to maybe completely get
rid of all type of nicotine products because it would put
Table 2 Superordinate themes and subthemes of participant opinions, beliefs, and intentions
Superordinate theme Subthemes
Intentions and motivations to stop smoking and/or use e-cigarettes Stopping smoking
Barriers to stopping smoking
Motivation to stop smoking
Motivation to use e-cigarettes
E-cigarettes are for smoking cessation
Trial of others’ e-cigarettes
Sensations and experience of using unflavoured e-liquid Throat hit and harshness of using unflavoured e-liquid
Unflavoured e-liquid satisfied cravings for nicotine
Unflavoured e-liquid satisfied cravings for cigarettes
Similarity to smoking
Expectations of unflavoured e-liquid
Opinion of unflavoured e-liquid
Potential use of unflavoured e-liquid to stop vaping
Ambivalence towards unflavoured e-liquid
Amount of unflavoured e-liquid used
Taste of unflavoured e-liquid and flavour preferences Appeal of flavours
Flavours are unappealing
Trial of other e-liquid flavours
Dislike of specific flavours
Flavour preferences
Unflavoured e-liquid is flavourless
Unflavoured e-liquid is not flavourless
Personal impact of a hypothetical flavour ban A flavour ban would affect likelihood of quitting smoking or relapse
A flavour ban would not affect likelihood of quitting smoking or relapse
A flavour ban is not a good idea
Flavour preferences in the event of a flavour ban
Amount of e-liquid would use if there was a flavour ban
Impact of a hypothetical flavour ban on others A flavour ban is a good idea
A flavour ban is not a good idea
Alternatives to smoking should be promoted not discouraged
Flavours are attractive to young people and people who do not smoke
Opinion of the gateway hypothesis
Comparing restrictions to other products and activities
Flavour preferences of others
Other drivers of vaping behaviour are more important than flavours People do not use e-cigarettes just because of the flavours
Effectiveness of the e-cigarette
Nicotine is more important than flavours
Ease of e-cigarette use
Health and addiction concerns
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Khoujaetal. Harm Reduction Journal (2024) 21:90
you off in a way […] but, I mean I genuinely would rather
have a cigarette.” Not all participants who vaped said
that unflavoured e-liquids are useful for stopping vaping.
P014V said “unflavoured liquid wouldn’t really help me in
any way to, to stop vaping because I’m still gonna crave
that nicotine hit, you know? If I wanted to stop vaping, I
would have to use patches.” P018V said, “if I was to wean
myself off vaping, I’d probably try and do it with one with
maybe like no nicotine in, […] but I would still go for a
flavoured one, I wouldn’t want the unflavoured.
Many participants who vaped reported that they used
their e-cigarette less than usual while using the unfla-
voured e-liquid. P004V thought during the 4-h trial
period they “vaped like nowhere near as much as I usu-
ally would in this time. Just because I think it wasn’t like
as much fun” and P006V said, “I don’t really wanna use
it.” P015V, P017V, P018V, P019V and P020V all thought
that they vaped less than usual too, but P016V vaped
“about the same” and P014V thought they vaped “a lot
more” which they reported was “because [of] the lack of
flavour, I wasn’t really getting the full satisfaction that I
normally get, so I was constantly on it.
Taste ofunavoured e‑liquid andavour preferences
Discussions of the taste of the unflavoured e-liquid and
participants’ own preferences for specific flavours versus
preferences among youth and those who do not smoke
formed a superordinate theme. ere was variety in the
flavours that participants disliked or preferred and many
described trialling different flavours when considering
using e-cigarettes and during their transition from smok-
ing to vaping. P010S said, “they’ve got all these flavours
so let’s try them”, and P007V described a process of “trial
and error” in finding the right flavour for them. Many
participants who vaped preferred “primarily the fruit
ones” (P004V), including one participant who initially
assumed they “wouldn’t have flavoured liquids, because it
doesn’t really mimic smoking” (P015V).
After trying the unflavoured e-liquid, some preferred
it to flavours such as menthol or fruit/sweet flavours,
but most preferred flavours. ere were individual dif-
ferences in which flavour participants stated they would
choose if only tobacco, menthol or unflavoured e-liquids
remained on the market; some stated tobacco, some
stated menthol, and some stated unflavoured, but some,
like P004V “would prefer to use cigarettes over [unfla-
voured e-liquid]”.
When prompted about the taste and flavour of the
unflavoured e-liquid, some participants described it
as “unflavoured”, “plain”, like “water” whereas some
described a “metallic” or “burnt” taste, and some
reported a hint of “sweetness”.
Many participants found the variety of flavours appeal-
ing when they initially decided to vape, and some par-
ticipants who smoked also discussed the appeal. P014V
found the variety of flavours available “extremely appeal-
ing”, P015V found “the variety quite helpful”, and P017V
said “there’s like so many different flavours and there’s
like you can have anything you want pretty much” which
“hundred percent” influenced their decision to vape and
made switching from smoking to vaping a “smoother
transition”. e appeal of flavours persuaded P013V to
make the switch due to the “nice smells”. P024S thought
they “would prefer vaping if it was flavoured.” Some
participants thought flavours also appealed to children
and people who do not smoke. P016V believed “like the
strawberry cheesecake ones […] they’d definitely appeal
to younger kids. I reckon that’s probably what they would
smoke if they did smoke them” and P020V thought “a
hundred percent, yeah, I think it does create an appeal
[to people who do not smoke]”. Not all participants found
vaping appealing (e.g., P002S found flavours “too sweet”)
and not all participants said that flavours appealed to
children either. P025S disagreed with the argument that
“because they’re young, they must go for fruit stuff” and
said “it’s more the adults that go for it, strangely enough,
because it reminds them of their childhood.
Personal impact ofahypothetical avour ban (excluding
tobacco andmenthol)
Some participants, particularly those who smoked, were
confident a ban on flavoured e-liquids (whereby unfla-
voured, tobacco flavoured, and menthol flavoured e-liq-
uids would remain on the market) would not personally
affect them. P011S said, “for people like me, you know
smokers, it wouldn’t bother me too much. P008S said, “I
could still erm use them to quit” but thought “it might
not be as encouraging.” ere were some participants
who vaped, particularly those who enjoyed using the
unflavoured e-liquid, who “would definitely keep to using
[unflavoured e-liquid], because it’s not harsh” (P013V).
Some participants who vaped, like P016V, did not feel
their quit attempt would have been hampered in this sce-
nario: “I do think I would [have successfully quit using an
e-cigarette], because you still get the hit off it […] I think
if I hadn’t tried flavoured, I wouldn’t know any differ-
ent.” Some participants’ confidence that they would not
be affected by flavour restrictions seemed to stem from
their commitment to never smoke again: “I’m definitely
out of that habit, I never, never want to go back to that
habit again” (P014V). Some felt that “enough time has
passed” since quitting that they may be able to cope with
the change (P007V). One participant discussed continu-
ing to make their own flavours if “ingredients were still
available” (P007V).
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Some participants reported that they would be neg-
atively impacted by flavour restrictions. Some who
smoked thought that they would not attempt to quit:
“if it was only unflavoured, I probably wouldn’t bother”
(P003S). A few participants who vaped suggested that
they may have never tried to quit smoking in this sce-
nario, for example P006V said “I probably wouldn’t
of bothered stopping smoking if that had been the
case.” Whereas some said they would have tried vap-
ing but “might not […] have been as successful at stop-
ping smoking” (P014V). Some participants who vaped
thought they would return to smoking like P019V who
would try “whatever was available… for a while, but
then I, I think I’d probably go back to smoking”. Some
participants who vaped “would just look towards quit-
ting” nicotine products entirely (P017V). A few par-
ticipants who vaped thought that a flavour restriction
would cause them to vape less, like P004V, who did not
think they “would vape nearly as much”. Some partici-
pants who vaped reported that they would try to access
flavoured e-liquids illegally like P015V, who said “I
would try and get it elsewhere if I was really motivated
[…] depends on how far along I was that I wanna quit,
but at this stage now, I would probably get it elsewhere
somehow.
Although some participants supported a restriction
on flavoured e-liquids in the UK, none stated personal
reasons for this. Many stated personal reasons for a ban
in the UK being a “bad idea”. When asked if flavours
should be banned in the UK, P018V said, “because
I vape and I vape the flavoured ones, I would say no.
Some thought we should not “be attacking what’s been
like a really good way to get people to quit smoking
and use something healthier” (P002S). Others thought
that people “should have a choice. It’s up to people to
choose to do possibly unhealthy things if they want to”
(P024S). P009V said, “selfishly I don’t want it to hap-
pen because I like Eton mess”, which echoed comments
from other participants who did not want their favour-
ite flavours to be removed. Some participants would
only be in support of a ban if “a causal link has been
established between [flavourings and] negative health
outcomes” (P007V). P016V thought “you could find
it if you wanted it” even if the flavours were banned.
Many suggested that they would be more supportive of
other restrictions and regulations over banning flavours
except from menthol and tobacco; instead of “com-
mand and control, […] monitoring it and regulating it”
(P011S). e alternative policies suggested by the par-
ticipants included adding age restrictions, stricter age
verification, reducing appeal of packaging, restricting
only some flavours which most appeal to youth, and
better marketing restrictions.
Impact ofahypothetical avour ban onothers (excluding
tobacco andmenthol)
Although participants did not see a personal benefit
resulting from restricting non-tobacco flavoured e-liq-
uids, some participants thought the hypothetical favour
ban would benefit youth as they thought some flavours
may appeal to children. P015V thought some flavours
should be banned because “strawberry laces, and things
like that, that’s just screaming to children, to me”. P003S
thought: “I see a lot of young people vaping. So, I do
think that removing them from the market probably
would help that, and I don’t think any kid would think it’s
very cool to be puffing on an unflavoured liquid.” P004V
spoke of friends who “didn’t really smoke and then they
started vaping like a lot just because it tastes nice and
like it’s something to fiddle with and it gives you like a
niccy rush and like serotonin rush” and thought a flavour
ban “would definitely be a good idea.” P021S thought that
“popular vape companies are aware of that these sort of
e-liquids are attractive for young children” and thought
“it should be banned if it’s something that’s getting out of
control.
Many participants thought that the benefit to youth did
not outweigh the benefit to adults who smoke or vape
who could use these flavours to refrain from smoking,
and some thought less harmful alternatives to smoking
should be promoted rather than discouraged. P002S said
“the benefits [of flavour availability] probably outweigh
the risks” and that vaping has “helped a lot of people quit
and [a number of people] demonstrably higher than sort
of any number you could conjure up of people who have
taken up smoking off the back of sort of starting with
flavoured e-liquid from when they were young.” P019V
wondered “are more people smoking now, [in countries
which have restricted flavours], because they haven’t got
the option to vape? Or what they want to vape, the fla-
vours they want to vape?” P007V thought “it wouldn’t
be helpful” and “it would slow down the rate of people
that are quitting smoking.” Although they “wouldn’t want
young people to start to vape” they would “want people
who smoke to, to do whatever it takes to stop smoking
and […] if they’re like me, then vaping’s been the only
thing […] that’s made that possible, so I would want to
give everyone else the opportunity to do that too.” P011S
thought “stopping young people from smoking is great
for future generations” but “the focus should also be on
current smokers, to stop them from smoking and try and
find an alternative means.” P015V thought that restrict-
ing all flavours could lead to increased “criminality”
and highlighted that any new policy “needs to be safe,
‘cause if they ban it completely then they’ll just open it
up for things to become very unsafe” for people who use
e-cigarettes.
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Not all participants said that the hypothetical restric-
tions would be beneficial to youth either, primarily
because they thought it would be ineffective in prevent-
ing vaping among youth. P023S thought the more you
tell young people “they can’t do something, the more
they’re likely to do it if anything.” P024S said, “if kids
wanna do something a bit rebellious or something they’re
not meant to do, they’re gonna do it anyway.” ey said
when they “first started smoking when I was 13… I just
did it, I didn’t go for the flavoured products, I just used
the regular ones because my friends were doing it.” P025S
thought that youth today are “social media’s [generation]
not the candyfloss generation. So, I don’t think it matters
whether you stop fruit.” ey thought if we keep associ-
ating flavours like “bubblegum and candyfloss with just
kids, then that works for the younger kids in that gen-
eration of like toddlers […] but, I think for the younger
teens… most of the stuff the parents think [they haven’t]
tried, they probably have.” ey said, “I don’t think if you
ban it, it will stop anything. ey will just go for the next
thing that’s available.” P010S said, “you’re not going to
stop young people from experimenting with tobacco or
anything, so, […] they would probably find something
that… had a flavour… that… in my guess would be some
weed.
Some participants thought that restrictions would be
ineffective, particularly if the aim was to prevent youth
from smoking, as they were sceptical about the gateway
hypothesis. P002S was “sort of sceptical of the sort of
like gateway argument” because “the flavour of flavoured
e-liquid is so drastically different to the actual flavour of
tobacco.” ey said, “if the only options are tobacco fla-
voured, then they’re more likely to find the adjustment
to… actually going onto smoking” easier. P019V thought
“vaping is definitely more appealing than smoking, but
then I can’t imagine why people would start smoking
after trying vaping. P011S said that it is hard to gener-
alise, it is not that “they have one puff on this flavoured
e-cigarette and that’s it, they’re hooked, they’re a smoker,
and you know… it’s all going to go downhill from there.
at’s… that’s not the case.” P008S said “it does the oppo-
site” and they knew “a lot of people that it has helped
[…]. Some of them have quit [smoking].” e experience
of P017V was more in line with the gateway hypothesis;
they “didn’t really smoke” and tried vaping because it was
“nicer”, “different”, “socially acceptable” and potentially
less harmful than smoking. ey then went through a
“cycle of smoking, vaping” and were supportive of a ban
on flavours to protect youth from smoking.
Some participants suggested alternative actions to take
instead of restricting flavours. P021S suggested increas-
ing awareness that the product is not for young people,
but they thought a ban should only be considered “if it
definitely would help kind of cut down the numbers of
children vaping.” P022S suggested using social media
to discourage youth vaping alongside other methods
because youth vaping is “a really complex problem, hence
it requires a complex solution.” Others thought we should
use existing regulations for other products as a guide.
P007V thought “regulations around smoking are more or
less appropriate” and they “should be similar for vaping.
P017V compared vaping regulations to alcohol regula-
tions: “when you buy alcohol and stuff and it’s delivered,
they like check your ID at the door, rather than just hand-
ing over like a crate of wine to a ten-year-old.” ey went
on to compare vaping to gambling, “like betting on your
phone, you have to go send your ID off, and your driving
licence off and it has to be linked to your bank account,
so, it’s definitely you. Why can similar things not be put
in place for buying alcohol, tobacco products?”.
Other drivers ofvaping behaviour are more important
thanavours
Participants identified other drivers of vaping behaviour
they thought were more important than flavours in the
appeal and use of e-cigarettes (with respect to themselves
or others). P007V said, flavours did not impact the rea-
son they started smoking so they “would be surprised if
flavour alone was influencing young people deciding to
start vaping.” e most common driver of vaping behav-
iour that participants thought was more important than
flavours was nicotine. Like many others, P014V was “vap-
ing to get the nicotine hit […] the flavours just a bonus
really.” P025S said, “flavours isn’t the issue, because it’s
the nicotine that’s the issue. […]. ere’s flavours out
there now, but… that’s not what’s causing the young peo-
ple to try it.
Health concerns (e.g., considering the comparative
health risks and benefits of vaping compared to smok-
ing) were prominent in the decision-making process of
whether to use e-cigarettes or not for some participants.
P001S was wary about e-cigarette use and “read loads of
articles saying that they like […] don’t really understand
them” which “scared” them. P020V said “there’s still risks
to vaping, but nowhere near as bad as smoking.” P013V
vaped because they “just thought it’s got to be healthier
for you than smoking.” Some stated that they would only
stop using flavoured products or vaping if “some like
scientific research was done, and it turned out that the
flavoured ones are very, very bad for you. You know, as
bad as smoking and they can damage the lungs whereas
the unflavoured ones, is very minimal damage” (P014V).
Some participants who smoked mentioned their con-
cerns about the potential addictiveness of e-cigarettes
which discouraged them from using e-cigarettes. For
example, P012S was wary that “if I did put a flavour in
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Khoujaetal. Harm Reduction Journal (2024) 21:90
here, my consumption would very much, like, increase
from it” because the unflavoured e-liquid was “not
that pleasant to do, but it still has the addictive quality.
Whereas if it was pleasant to do, and had the addictive
quality” they would use it more. Some thought health
concerns could feed into the decisions young people
make too. P010S thought “young people these days […]
tend to be a lot healthier” and would therefore be more
wary of trying e-cigarettes. Some thought that the lesser
health risks were reason to not be concerned if youth
vaped instead of smoked. P002S said, “I don’t believe that
there’s a lot of people that are picking up sort of e-ciga-
rettes just because it’s flavoured” and if they were “there’s
not much reason to believe it’s […] that harmful to health
and if it is then it’s certainly most likely less harmful than
if they were to pick up smoking.
More often, however, participants thought the trendi-
ness of e-cigarettes and peer pressure were the biggest
drivers influencing e-cigarette use among young people.
P001S suggested “it probably is just because they are
sweet and then they look cooler or something.” P019V
proposed people who do not smoke vape because “it’s
like a peer pressure thing” and P025S said: “this is the
social media generation, so, everything’s a hype” so
young people will do “whatever they see the celebrities
do” and “the celebrities don’t look like they’re stopping
anytime soon. So, it’s the new thing.” P022S recalled that
after watching films and TV, “seeing imagery of people
smoking […] to some extent just subconsciously I started
mimicking them in some way and I haven’t really seen
anyone vaping.” P023S suggested “there should be [senior
male celebrity] on the BBC smoking flavoured vapes to
make it as uncool as possible” to discourage youth use.
Other drivers of vaping behaviour discussed included
the ease of vaping, cost of vaping, the social acceptabil-
ity, the effectiveness of the device, to get breaks at work,
behavioural aspects, and peer pressure (Additional file1,
Sect.2.2).
Discussion
is study provides an insight into the potential impact
of e-liquid flavour restrictions in the UK. At a time when
there is considerable pressure on the UK government
to address the rise in e-cigarette use among young peo-
ple, this study indicates the impact of a flavour ban from
the perspectives of people who have used and could use
e-cigarettes to quit smoking. When making policy deci-
sions, it is important to consider evidence such as this
to avoid negative consequences and increase the likeli-
hood of the policy reducing population-level harm. We
found six superordinate themes which centred around
the intentions and motivations to stop smoking and vap-
ing, the sensations and experience of vaping unflavoured
e-liquid, the taste of unflavoured e-liquid and flavour
preferences, the negative impact of flavour restrictions
on the participants, the positive and negative impact of
flavour restrictions on others, and other drivers of behav-
iour being more important than flavours.
Our findings are consistent with previous evidence
suggesting that the experiential aspects of e-liquids are
important and could influence behaviour. For example,
the harshness of the unflavourede-liquid was discussed
by participants. Previous research has shown that harsh-
ness of e-liquids is a quality that is disliked by people
who use e-cigarettes [29], but throat hits can be pleas-
ant or unpleasant for people who smoke, and finding the
optimal throat hit is associated with increased desire to
quit smoking using e-cigarettes [16]. Our results suggest
unflavoured e-liquids may be too harsh for people who
use e-cigarette who have adjusted to less harsh, flavoured
e-liquids and not harsh enough for some people who
smoke who enjoy a strong throat hit. e unflavoured
e-liquid was sufficient to satisfy some participants’ crav-
ings for nicotine and cigarettes, as we have found previ-
ously [18], but they were not as enjoyable for some who
currently use flavoured e-liquids. Some participants felt
that the switch from smoking to vaping was made easier
because of the similarities between the two behaviours,
but the desire to mimic cigarettes may decrease over
time. Some participants who smoked had tried vaping
but stopped because the flavour differed from smoking,
whereas those who continued to vape seemed to prefer
there to be a difference in flavour. When initially quitting,
similarity to smoking and tobacco flavour may be impor-
tant, but Farsalinos etal. [19] found that flavour variabil-
ity is very important to people who use e-cigarettes who
have successfully stopped smoking. In line with our find-
ings, other research has shown people who smoke report
using a preferred flavour when starting to vape, which
may take some trial and error to find, but some people
continue to seek variety [8] and many people who vape
regularly use multiple flavours [17, 43, 44]. Our survey
results support this, with most participants reporting
using a variety of flavours rather than one specific fla-
vour (Additional file2: TableS5). Some participants who
vaped claimed they vaped less than they usually would
when using the unflavoured e-liquid provided. Infrequent
vaping is associated with greater risk of relapsing to
smoking compared to frequent vaping [10], so changes in
frequency of use due to flavour restrictions could impact
the likelihood of relapse to smoking.
As suggested by many of the participants, current
evidence suggests that flavours other than tobacco and
menthol appeal to non-smoking young people as well as
adults who smoke and/or vape [30, 35, 36], but the par-
ticipants raised many potential issues that could arise
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Page 13 of 16
Khoujaetal. Harm Reduction Journal (2024) 21:90
from a restriction on e-liquid flavours which could ulti-
mately result in increased population-level harm. One
potential issue raised was that the restrictions may lead
more people to start or continue to smoke cigarettes.
Consistent with this perception, flavour restrictions in
San Francisco were reportedly followed by reductions in
e-cigarette use but increases in smoking among young
adults [22, 54]. Buckell etal. [12] found that while flavour
restrictions could reduce choice of e-cigarettes by 11%
they could also increase choice of cigarettes by 8% among
people who smoke or have recently quit. Another poten-
tial issue was that some thought they would make their
own e-liquids or obtain them illegally, which reflects what
occurred in Finland, where 43% of people who vaped in
the year after flavour restrictions were introduced used
banned flavours [42]. e use of illicit and adulterated
e-cigarette products, and products from informal sources
can expose people to additional harms: 2,807 people were
hospitalised, and 68 people were killed during the e-ciga-
rette and vaping associated lung injury (EVALI) outbreak
(July 2019 to February 2020), when vitamin E acetate was
added to e-cigarettes to vape Delta-9-tetrahydrocannab-
inol [THC] instead of nicotine [9]. For these reasons,
some participants did not think flavours being restricted
in the UK was a good idea, in line with survey data from
the International Tobacco Control (ITC) study which
found that a ban on non-tobacco flavours would be
strongly opposed by more than 81% of people who vape
[26].
Despite the potential issues raised, some participants
were still supportive of flavour restrictions to discour-
age youth from initiating vaping. In line with these
participants’ opinions, after flavour restrictions were
introduced in Finland, e-cigarette use has remained low
among 15- to 69-year-olds [42], and the prevalence of
e-cigarette use among young adults has decreased among
young adults since the ban in San Francisco and other US
states [13, 54]. Other participants suggested that alter-
native measures could be more effective, and that there
are other more important drivers of vaping behaviour
than flavours, such as health concerns and trendiness.
e alternative measures suggested, such as increased
age restrictions and stricter marketing regulations, have
been implemented in other countries with varying suc-
cess [53]. Patel etal. [37] found 85% of US adults who
vape cited health and smoking cessation as a reason for
using e-cigarettes, 57% cited convenience, and 34% cited
flavouring. Although younger adults (18–24years) were
more likely to cite flavours (46%) than the older adults,
they were more likely to report health/cessation (73%)
and convenience (55%) as reasons for use [37]. In UK
adults, a reduction in beliefs that e-cigarettes are less
harmful than combustible cigarettes was associated with
a decrease in the prevalence of e-cigarette use. Trendi-
ness has also been reported to influence youth use both
in the UK and US in qualitative interviews with youth
[11, 49].
is study allowed us to explore various experiences
and opinions from people of different ages (19–62years)
and people with different smoking and vaping histories,
however, the participants were predominantly White.
We acknowledged that few people who vape in the UK
use unflavoured e-liquids, so participants tried an unfla-
voured e-liquid before commenting on flavour restric-
tions that would exclude unflavoured e-liquids.
Although participants were allowed to trial the unfla-
voured e-liquid for 4 h, taste profiles can change after
stopping smoking, so the findings may have been
impacted by the short trial period as well as the lack of
tobacco and menthol e-liquid provision, the use of unfa-
miliar devices, and potential device malfunctions. Par-
ticipants who smoked were only offered unflavoured
e-liquid and not flavoured e-liquid and they did not
receive a live demonstration or live advice on how to
use the e-cigarette, which could have influenced their
responses. Although eight out of twelve of these par-
ticipants had tried vaping (and had likely experienced
flavoured e-liquids before), the inhalation processes can
considerably differ between smoking and vaping with
increased experience [20], so participants may have had
a more positive experience with further guidance on
how to use the product. ese findings are reflective of
the participants subjective estimation of the impact of a
hypothetical restriction rather than an objective obser-
vation of the impact, and the research was conducted
before the UK government announced plans to restrict
flavours. Future research could explore the potential
impact of other restrictions which have been announced
by the UK government, such as restricting the sale of dis-
posable e-cigarettes, to identify which regulations may
have the least negative impact on people who currently
smoke and vape. e impact of unflavoured versus fla-
voured e-liquids on vaping frequency and smoking cessa-
tion could also be explored.
Conclusions
In conclusion, there are differences in how individu-
als who smoke or vape perceived they may be impacted
by e-liquid restrictions in the UK. Some believed they
would be unaffected as they would use unrestricted fla-
vours or continue to smoke, but some felt they would
be at greater risk of relapsing to smoking or continuing
smoking rather than quitting with an e-cigarette. Most
participants seemed to support the prevention of young
people from starting to vape, but they had differing opin-
ions on whether restricting flavours would be an effective
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Page 14 of 16
Khoujaetal. Harm Reduction Journal (2024) 21:90
method to discourage youth vaping. ese results reflect
participant perceptions of the impact of a flavour ban,
but actual behaviour in the event of a restriction may dif-
fer. Nevertheless, the subthemes identified here could be
used to guide further research into the impact of flavour
restrictions which could be used to aid policy decisions
to reduce harm related to smoking and vaping.
Abbreviations
BBC British Broadcasting Company
CPD Cigarettes per day
E-cigarettes Electronic Cigarettes
IPA Interpretative Phenomenological Analysis
ITC International Tobacco Control
PG Propylene glycol
TARG Tobacco and Alcohol Research Group
UK United Kingdom
US United States
USA United States of America
USB Universal Serial Bus
VG Vegetable glycerin
Supplementary Information
The online version contains supplementary material available at https:// doi.
org/ 10. 1186/ s12954- 024- 01003-z.
Additional le1.contains supplemental texts relating to methods
(Sect. 1) and supplementary themes (Sect. 2).
Additional le2. contains Supplementary Tables S1–S5.
Acknowledgements
We would like to acknowledge the work of two undergraduate students, Mol-
lie Simmonds and Georgia Laidlaw, who provided input into the development
of the study, were involved in data collection and assisted in the analysis of
the data.
Author contributions
JK, MD, AA, and MM contributed to the development of the study protocol
and study documents. With the assistance of two undergraduate students,
JK conducted the qualitative interviews, transcribed the audio recordings,
and coded the data. Disputes in the transcriptions or coding were resolved
between the two students and JK. JK drafted the manuscript and all authors
contributed to and approved the final manuscript.
Funding
This work was supported by Public Health England (PHE) via an honorary
contract awarded to AA. There is no grant number for this research as it was
commissioned by Public Health England via the honorary academic frame-
work. PHE were not involved in the conception or design of the study, data
analysis or interpretation of the study findings. The MRC Integrative Epidemiol-
ogy Unit (MRC IEU) at the University of Bristol provided wider support to this
research (MC_UU_00011/7). This work was also supported by Cancer Research
UK [Grant Number C18281/A29019].
Availability of data and materials
Data are available at the University of Bristol data repository, data.bris, at
https:// doi. org/ 10. 5523/ bris. 1hr9w euiqm iq523 44a0w czg00i.
Declarations
Ethics approval and consent to participate
This study was reviewed by the School of Psychological Science Human
Research Ethics Committee, a subcommittee of the Faculty of Life Sciences
Ethics Committee (reference: 010421116008). All participants provided written
consent to participate.
Consent for publication
All participants provided written consent to the publication of these findings.
Competing interests
The authors have no competing interests to declare.
Author details
1 School of Psychological Science, University of Bristol, 12a Priory Road,
Bristol BS8 1TU, UK. 2 Medical Research Council Integrative Epidemiology Unit,
University of Bristol, Bristol BS8 2BN, UK. 3 Department of Health and Social
Care, Office of Health Improvement and Disparities, London SW1H 0EU, UK.
4 NIHR Biomedical Research Centre at the University Hospitals Bristol NHS
Foundation Trust and School of Psychological Science, University of Bristol, 12a
Priory Road, Bristol BS8 1TU, UK.
Received: 11 September 2022 Accepted: 8 April 2024
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Article
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Background China has banned all flavoured e-cigarettes to reduce e-cigarette use among young people, but little is known about the views and reactions of people who use e-cigarettes. This study explored the perceptions of, and responses by, young adults who use e-cigarettes to the flavour ban. Methods Semistructured interviews were conducted with 25 Chinese young adults aged 18–25 years who had used e-cigarettes daily in the past 3 months. Thematic analysis was used to analyse the interview data. Findings Four themes were identified from the data: (1) understanding of the public health benefits, (2) resistance to and misperceptions of the flavour ban, (3) circumvention of the flavour ban and (4) acceptance of the flavour ban. Some participants expressed support for the ban due to perceived public health benefits, while others who resisted the ban emphasised their right to choose preferred flavours and questioned the rationale behind the policy. Participants responded to the flavour ban by utilising a variety of adaptive strategies, including purchasing flavoured e-cigarettes through illegal channels or exploring alternative ways to obtain flavours. Those who complied with the ban responded with different strategies, including switching back to combustible cigarettes, using tobacco-flavoured e-cigarettes, or quitting vaping. Conclusions The findings suggest the need for comprehensive regulatory measures, including stringent enforcement measures, transparent health communication and vigilant monitoring of e-cigarette manufacturers’ tactics, to reduce e-cigarette use among young adults.
Article
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Background: The rapid increase in electronic nicotine product (ENP) use among young people has been a global public health challenge, given the potential harm of ENPs and nicotine dependence. Many countries have recently introduced legislations to regulate ENPs, but the impacts of these policies are poorly understood. This systematic review aims to critically synthesise empirical studies on the effects of global regulations regarding ENPs on the prevalence of use, health outcomes and their determinants, using the 4A marketing mix framework (acceptability, affordability, accessibility and awareness). Methods: Following the PRISMA guideline, we searched PubMed, Embase, Scopus, Web of Science, Academic Search Complete, Business Source Complete, and APA PsycINFO databases from inception until June 14, 2022 and performed citation searches on the included studies. Reviewed literature was restricted to peer-reviewed, English-language articles. We included all pre-post and quasi-experimental studies that evaluated the impacts of e-cigarette policies on the prevalence of ENP use and other health outcomes. A modified Joanna Briggs Institute (JBI) Critical Appraisal checklist for quasi-experimental studies was used for quality assessment. Due to heterogeneity of the included studies, we conducted a narrative synthesis of evidence. Results: Of 3991 unduplicated records screened, 48 (1.2%) met the inclusion criteria, most were from high-income countries in North America and Europe and 26 studies measured self-reported ENPs use. Flavour restrictions significantly decreased youth ENP use and taxation reduced adult use; mixed results were found for the impacts of age restrictions. Indoor vaping restrictions and the European Tobacco Products Directive (TPD) did not seem to reduce ENP use based on existing studies. Changes in determinants such as sales and perceptions corroborated our conclusions. Few studies assessed the impacts of other regulations such as advertising restrictions and retail licensing requirements. Conclusions: Flavour restrictions and taxes have the strongest evidence to support effective control of ENPs, while others need powerful enforcement and meaningful penalties to ensure their effectiveness. Future research should focus on under-examined policies and differential impacts across sociodemographic characteristics and countries. Registration: PROSPERO CRD42022337361.
Article
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Electronic cigarettes (e-cigarettes) are devices that allow the user to inhale nicotine in a vapor, and are primarily marketed as a means of quitting smoking and a less harmful replacement for traditional cigarette smoking. However, further research is needed to determine if vaping nicotine via e-cigarettes can be effective. Conversely, nicotine has been considered a gateway drug to alcohol and other addictive drugs and e-cigarettes containing nicotine may have the same effects. Previous reports have shown that e-cigarette use may open the gate for the use of other drugs including conventional cigarettes, cannabis, opioids, etc. The increasing prevalence of e-cigarettes, particularly among youth and adolescents in the last decade have led to an increase in the dual use of e-cigarettes with alcohol, cannabis, and other illicit drug use like heroin and 3-4-methylenedioxymethamphetamine (MDMA). The advent of e-cigarettes as a device to self-administer addictive agents such as cocaine and synthetic cathinones may bring about additional adverse health effects associated with their concurrent use. This review aims to briefly describe e-cigarettes and their different generations, and their co-use with other addictive drugs as well as the use of the device as a tool to self-administer addictive drugs, such as cocaine, etc.
Research
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This evidence review is the eighth in a series of independent reports on vaping originally commissioned by Public Health England and now by the Office for Health Improvement and Disparities in the Department of Health and Social Care. This report was led by academics at King’s College London with a group of international collaborators and is the most comprehensive to date. Its main focus is a systematic review of the evidence on the health risks of nicotine vaping.
Chapter
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A range of regulatory approaches are being applied to e-cigarettes globally. This chapter examines the reasons for this and what this means for broader tobacco control efforts. The chapter starts with a discussion of tobacco control and how evidence has influenced the development of international tobacco control policies. The chapter then explores the development and emergence of e-cigarettes. It identifies and discusses the arguments and evidence used in the e-cigarette regulatory debates. The chapter concludes by suggesting that research in this domain could improve our understanding of what factors influence the regulatory environment, thus why different regulatory approaches as pursued.
Article
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Objective To synthesize the outcomes of policy evaluations of flavoured electronic nicotine delivery systems (ENDS) restrictions. Data sources PubMed, Scopus, Embase and Web of Science before May 3, 2022. Study selection Studies that report sales, behaviour, or compliance outcomes related to implemented or hypothetical ENDS flavour restrictions. Data extraction Restriction details, whether implemented or hypothetical, whether additional products were restricted, jurisdictional level, study locations, and outcomes classified by sales, behaviour, and compliance. Data synthesis We included 30 studies. Of those, 26 were conducted exclusively in the US, two in India, and two surveyed respondents in multiple countries, including the US. Twenty-one evaluated implemented restrictions, while nine considered hypothetical restrictions. Five studies evaluated product sales, 17 evaluated behaviour, and 10 evaluated compliance, with two studies reporting multiple outcomes. Two studies reported an increase and one a reduction in cigarette sales following restrictions, while three reported reductions in ENDS sales. Behavioural studies presented a mixed view of the impacts of regulations on ENDS and cigarette use. However, the use of disparate outcomes limits the comparability of studies. Studies of hypothetical restrictions suggest decreased ENDS use, increased cigarette use, and increased use of illicit markets. Studies of compliance with flavoured product restrictions that included ENDS found that 6–39% of stores sold restricted flavoured products post-restrictions. Online stores remain a potential source of restricted products. Conclusion Our findings highlight the need for additional research on the impacts of ENDS restrictions. Research should further evaluate the impact of restrictions on youth and adult use of nicotine and tobacco products in addition to the effects of restrictions in countries beyond the US to enable a robust consideration of the harm-benefit trade-off of restrictions.
Preprint
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Background: Policy decisions should be evidence-based, but the magnitude of intended and unintended impacts cannot always be easily estimated from the available data. For example, banning flavours in electronic cigarettes (e-cigarettes) to reduce appeal to non-smoking young people could have the intended impact by reducing youth vaping but could have negative consequences for adult smokers and vapers. Methods: We developed a decision aid to help policymakers make informed decisions on the potential net impact of a ban on e-cigarette flavours. We estimated the number of non-smoking youth who would be deterred from ever vaping and subsequently ever smoking, and the number of smokers and ex-smokers who would be deterred from quitting or encouraged to relapse, to determine whether the benefits to youth outweigh the costs to existing smokers and vapers. This aid then outputs a report with the results graphically depicted to aid interpretability. Results: We demonstrated the value of this decision aid using data from various sources to estimate the impact of a flavour ban in three populations: the general UK population, low-socioeconomic position UK population, and the general US population. All three examples suggested a negative net population impact of a ban. These reports were then presented to the all-party parliamentary group for vaping. Discussion: We demonstrate how decision aids can be used to help policymakers arrive at evidence-based decisions efficiently and can be used to quickly obtain up-to-date estimates as new data becomes available.
Article
Background: Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. People who smoke, healthcare providers and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review. Objectives: To examine the safety, tolerability and effectiveness of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence, in comparison to non-nicotine EC, other smoking cessation treatments and no treatment. Search methods: We searched the Cochrane Tobacco Addiction Group's Specialized Register to 1 February 2023, and Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 July 2023, and reference-checked and contacted study authors. Selection criteria: We included trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention as these studies have the potential to provide further information on harms and longer-term use. Studies had to report an eligible outcome. Data collection and analysis: We followed standard Cochrane methods for screening and data extraction. Critical outcomes were abstinence from smoking after at least six months, adverse events (AEs), and serious adverse events (SAEs). We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in pairwise and network meta-analyses (NMA). Main results: We included 88 completed studies (10 new to this update), representing 27,235 participants, of which 47 were randomized controlled trials (RCTs). Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 58 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There is high certainty that nicotine EC increases quit rates compared to nicotine replacement therapy (NRT) (RR 1.59, 95% CI 1.29 to 1.93; I2 = 0%; 7 studies, 2544 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6 more). There is moderate-certainty evidence (limited by imprecision) that the rate of occurrence of AEs is similar between groups (RR 1.03, 95% CI 0.91 to 1.17; I2 = 0%; 5 studies, 2052 participants). SAEs were rare, and there is insufficient evidence to determine whether rates differ between groups due to very serious imprecision (RR 1.20, 95% CI 0.90 to 1.60; I2 = 32%; 6 studies, 2761 participants; low-certainty evidence). There is moderate-certainty evidence, limited by imprecision, that nicotine EC increases quit rates compared to non-nicotine EC (RR 1.46, 95% CI 1.09 to 1.96; I2 = 4%; 6 studies, 1613 participants). In absolute terms, this might lead to an additional three quitters per 100 (95% CI 1 to 7 more). There is moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 1840 participants). There is insufficient evidence to determine whether rates of SAEs differ between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 9 studies, 1412 participants; low-certainty evidence). Due to issues with risk of bias, there is low-certainty evidence that, compared to behavioural support only/no support, quit rates may be higher for participants randomized to nicotine EC (RR 1.88, 95% CI 1.56 to 2.25; I2 = 0%; 9 studies, 5024 participants). In absolute terms, this represents an additional four quitters per 100 (95% CI 2 to 5 more). There was some evidence that (non-serious) AEs may be more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low-certainty evidence; 4 studies, 765 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 0.89, 95% CI 0.59 to 1.34; I2 = 23%; 10 studies, 3263 participants; very low-certainty evidence). Results from the NMA were consistent with those from pairwise meta-analyses for all critical outcomes, and there was no indication of inconsistency within the networks. Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons, hence, evidence for these is limited, with CIs often encompassing both clinically significant harm and benefit. Authors' conclusions: There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain due to risk of bias inherent in the study design. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but the longest follow-up was two years and the number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.
Article
"E-Cigarette (e-cig) Vaping-Associated Acute Lung Injury" (EVALI) has been linked to vitamin-E-acetate (VEA) and Δ-9-tetrahydrocannabinol (THC), due to their presence in patients' e-cigs and biological samples. Lacking standardized methodologies for patients' data collection and comprehensive physicochemical/toxicological studies using real-world-vapor exposures, very little data are available, thus the underlying pathophysiological mechanism of EVALI is still unknown. This review aims to provide a comprehensive and critical appraisal of existing literature on clinical/epidemiological features and physicochemical-toxicological characterization of vaping emissions associated with EVALI. The literature review of 161 medical case reports revealed that the predominant demographic pattern was healthy white male, adolescent, or young adult, vaping illicit/informal THC-containing e-cigs. The main histopathologic pattern consisted of diffuse alveolar damage with bilateral ground-glass-opacities at chest radiograph/CT, and increased number of macrophages or neutrophils and foamy-macrophages in the bronchoalveolar lavage. The chemical analysis of THC/VEA e-cig vapors showed a chemical difference between THC/VEA and the single THC or VEA. The chemical characterization of vapors from counterfeit THC-based e-cigs or in-house-prepared e-liquids using either cannabidiol (CBD), VEA, or medium-chain triglycerides (MCT), identified many toxicants, such as carbonyls, volatile organic compounds, terpenes, silicon compounds, hydrocarbons, heavy metals, pesticides and various industrial/manufacturing/automotive-related chemicals. There is very scarce published toxicological data on emissions from THC/VEA e-liquids. However, CBD, MCT, and VEA emissions exert varying degrees of cytotoxicity, inflammation, and lung damage, depending on puffing topography and cell line. Major knowledge gaps were identified, including the need for more systematic-standardized epidemiological surveys, comprehensive physicochemical characterization of real-world e-cig emissions, and mechanistic studies linking emission properties to specific toxicological outcomes.