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R E V I E W Open Access
Electronic cigarettes: patterns of use, health
effects, use in smoking cessation and
regulatory issues
Muhammad Aziz Rahman
1,2*
, Nicholas Hann
3
, Andrew Wilson
2,3,4
and Linda Worrall-Carter
1,2,4
Abstract
Background: Electronic cigarettes (e-cigarettes) are battery-powered devices that vaporize a liquid solution to
deliver a dose of inhaled nicotine to the user. There is ongoing debate regarding their regulation.
Objectives: This comprehensive narrative review aimed to discuss key issues including usage patterns, health
effects, efficacy in smoking cessation and regulatory concerns with a view to informing future regulation and
research agendas.
Methods: PubMed, Scopus and Web of Science databases were searched using the terms (electronic cigarettes OR
e-cigarettes) for articles in English, relevant to humans and published during January 2009-January 2014.
Results: The literature search revealed 37 relevant articles. Findings suggest that e-cigarettes are mostly used by
middle-aged current smokers, particularly males, to help them for quitting or for recreation. E-cigarettes contain very
low levels of multiple toxic substances such as formaldehyde and acrolein, but these levels are many times lower than
those found in cigarettes. They were found to have effectiveness in aiding smoking cessation to a limited degree.
Debate continues regarding regulating their use for cessation versus heavy restrictions to control recreational use on
the basis that it perpetuates nicotine addiction.
Conclusions: The cytotoxicity and long term health effects of e-cigarettes are unknown. Nevertheless the e-cigarette
market continues to expand, largely driven by middle-aged smokers who claim to be using e-cigarettes in an attempt
to reduce or quit smoking. E-cigarettes may have some potential as smoking cessation aids and, in the researchers’
view, should therefore be subject to further research and regulation similar to other nicotine replacement therapies.
Keywords: E-cigarettes, Electronic cigarettes, Smoking, Smoking cessation, Tobacco
Background
E-cigarettes are battery-powered cigarette-shaped de-
vices that vaporize a liquid solution which is inhaled or-
ally to deliver a dose of nicotine to the user. The liquid
solution, contained in a cylindrical cartridge, generally
consists of propylene glycol in which nicotine and other
aromas may be dissolved (Figure 1). The solution is va-
porized when the user puffs on the device, activating a
battery-powered heating element [1,2]. The devices are
available both in a cigarette-shaped form and newer
‘tank’form which replaces the cylindrical cartridge with
a larger solution tank, allowing the user to refill less fre-
quently [3]. As tobacco leaves are not combusted in this
process, manufacturers claim the resulting vapor is free
of the 4000 toxic chemicals and carcinogens known to
be produced by combustion in cigarettes [4].
E-cigarettes were invented by Chinese pharmacist Hon
Lik in 2003, and subsequently became available globally,
entering the European (EU) and American (US) markets
in 2006 and 2007 respectively [1,5]. Their use has grown
rapidly; Google searches for ‘e-cigarettes’increased by
5000% during 2011-12, 18% of US smokers have tried
them and as of 2013 the industry is worth $2 billion in
the US [6,7]. This market growth in use is due in part to
the implementation of novel marketing campaigns by e-
* Correspondence: drazizdmc@gmail.com
1
St Vincent’s Centre for Nursing Research (SVCNR), Australian Catholic
University, Melbourne, Australia
2
The Cardiovascular Research Centre (CvRC), Australian Catholic University,
Melbourne, Australia
Full list of author information is available at the end of the article
© 2014 Rahman et al.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain
Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article,
unless otherwise stated.
Rahman et al. Tobacco Induced Diseases 2014, 12:21
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cigarette manufacturers, including large tobacco com-
panies that own some e-cigarette producers [7]. Indeed,
in absence of market regulation, $15.7 million was spent
on e-cigarette advertising by US manufacturers in the
first quarter of 2013 alone [7].
There is much debate about the potential of e-cigarettes
in various capacities, but given the relative paucity of sci-
entific research investigating their safety and efficacy, they
present a pressing dilemma to regulatory authorities. On
the one hand, they have the potential to become a valuable
smoking cessation aid and contribute to the momentum
of existing tobacco control programs [8]. One study
showed them to be as effective as nicotine patches in help-
ing smokers to quit and superior to nicotine patches in re-
ducing the number of cigarettes individuals smoked [9].
Conversely, there is concern that as long as they are un-
regulated, e-cigarettes may serve to re-normalize and re-
glamorize smoking to vulnerable youth and developing
world populations, thereby undermining the success of to-
bacco control activities [10].
Current debate about the devices is focused on their
regulation, with a decision having been made in the EU
and regulations set to be decided on in the US in mid-
2014. Regulatory decisions will closely dictate the trajec-
tory of the e-cigarette, both as a tool in tobacco harm
reduction strategies and as a commercial product [6,11].
Public health researchers favoring the devices’role in
smoking cessation are arguing for a compromise of mea-
sured regulation, at least at the outset, so as not to regu-
late the products out of existence [11]. Proponents of
this argument cite unexpected consequences of existing
laws on nicotine replacement products which they argue
make them so restricted and unappealing that they act
as a disincentive to quit smoking [11]. On the other
hand, researchers that are skeptical of the devices’po-
tential role in tobacco harm reduction are arguing for
strict regulation. They liken e-cigarettes to filtered and
light cigarettes which were marketed as harm reduction
strategies, but actually acted as disincentives to quitting
and rather augmented tobacco use [6].
The objective of this paper is to provide a comprehen-
sive narrative review of the existing literature pertaining
to e-cigarettes, including usage patterns, motivations for
use, health effects, potential role in smoking cessation
and a summary of the current regulatory debate. By col-
lating the findings of key research in these areas, this
paper aims to inform regulatory decisions and highlight
areas for further investigation.
The device
Figure 1 illustrates the components of a standard
e-cigarette. When the user inhales, airflow is created
which activates the flow trigger. Then the LED light turns
on and the heating element vaporizes the solution in the
cartridge (which contains propylene glycol, nicotine and
sometimes flavorings) into mist. The nicotine containing
mist is then inhaled by the user [15]. Refill solutions in
nicotine cartridges have been shown to contain low levels
of several toxic substances [12-14]. These substances in-
clude carbonyl compounds, volatile organic compounds,
nitrosamines, ultrafine particulate matter and heavy metals
[4,12-14]. These substances are of interest because they
are known to be implicated in various disease processes.
For example, carbonyl compounds detected include for-
maldehyde and acetaldehyde (known to be carcinogenic)
and acrolein (implicated in the pathogenesis of cardiovas-
cular diseases) [12]. Propylene glycol acts as the humec-
tants in most refill solutions and whilst it is not cytotoxic
in its liquid form, it has been found to exacerbate allergic
respiratory symptoms including rhinitis and asthma, and
the safety of inhaling its vaporized form, especially in the
long-term, has not been tested in humans [13,15].
Methods
PubMed, Scopus and Web of Science databases were se-
lected as the primary databases. We used the following
Figure 1 Components of an electronic cigarette.
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search terms: (electronic cigarettes OR e-cigarettes). Fields
were limited to ‘title and abstract’for PubMed with
‘keywords’also included for Scopus. We used 'topic' field
for Web of Science searches. Searches were limited to
English language, humans and published in the five years
from January 2009 to January 2014. Our objective was to
find articles on e-cigarettes which focused on the aims of
this paper. Inclusion criteria were: articles focused on
e-cigarettes specifically (not other smoking cessation the-
rapies) and focused on any of the five key themes (usage
patterns, motivations for use, health effects, potential role
in smoking cessation and the current regulatory debate)
according to the objective of this manuscript. Firstly, titles
and abstracts were assessed, and then articles were in-
cluded or excluded based on their relevance. The literature
search revealed 37 relevant articles. Each of the articles was
reviewed in details and summarized according to our five
themes.
Review
Patterns of use
Available research on patterns of use is limited; some re-
searchers quantify the amount of use, e.g. daily, occasional
or experimental use, whereas others merely measure ever-
versus never-use, which provides less robust information
on usage patterns. Of the nine reviewed studies that in-
vestigated patterns of use, four quantified use by distin-
guishing among daily, occasional and experimental use,
which is important to consider when discussing their
findings [3,16-18].
Six of the seven studies investigating smoking status
found that e-cigarette use was more prevalent among
current and former smokers than among never smokers
[3,17,19-23]. In one study, 21% of current smokers were
using e-cigarettes compared with 7% of former smokers
and 1% of never smokers [20]. Although that does not
rule out their role as bridging products for current
smokers, it tends to discount the notion that the devices
are being used by large numbers of never smokers as
gateway products to further nicotine and tobacco use
[24,25]. The one exception to this trend is the study by
Sutfin et al. which investigated e-cigarette use among uni-
versity students [23]. Although ever-use of e-cigarettes
among the sample of 4,444 students was low (4.9%), 12%
of those e-cigarette users were never smokers [23]. Dutra
et al also showed that e-cigarette use was associated with
lower odds of abstinence from cigarette smoking among a
large population of US school students [16].
There is reasonable consensus in the literature regard-
ing the age profile of e-cigarette users, indicating that
most users are current smokers. Seven studies investi-
gated age and all found that use of e-cigarettes increased
significantly during the third to fifth decades of life, and
then declined [3,17,19-23]. Three studies reported the
median age of e-cigarette use between 40 and 50 years
[3,17,18]. Studies investigating use among young people
reported variable rates of use among adolescents [19,22,
26,27] with two studies reported rates less than 1%
[19,22]. However, Lee et al. found that 9% of Korean ado-
lescents ever used e-cigarettes and 5% used within last
month [27]. Furthermore, Goniewicz et al found that al-
most one in four (24%) Polish high school students aged
15-19 years had tried e-cigarettes and 8% had done so
within last month [26]. It also needs to be acknowledged
that there is lack of most recent data on e-cigarette use
among adolescents and it is unknown whether popularity
of e-cigarettes has increased in this group.
Two studies assessed demographic variables and re-
ported similar findings in terms of gender, socioeco-
nomic status and geographical distribution of e-cigarette
users [20,23]. Two studies found that use was signifi-
cantly more common among males, but that there was
no significant difference in use according to the level of
education or income [3,17]. Studies suggest that e-
cigarette use is concentrated in Europe and the US, with
a small but significant level in Brazil [3]. Within the US,
there does not appear to be any significant difference in
use according to geographical location [17].
Motivation for use
There is conjecture about consumers’motivation for
using e-cigarettes, with one body of research suggesting
people are using them to quit smoking [3,17,18,28],
while another expresses concern that a great deal
of e-cigarette use is recreational rather than quit-
related [21,23].
Several studies demonstrated the recreational element
of e-cigarette use. In one study that included two sur-
veys of more than 3500 e-cigarette users, only one
showed a marginally significant correlation between use
and a quit attempt in the last three months [21]. Sutfin
et al. studied university students (42% of whom were
current smokers) and found no established association
between e-cigarette use and intention to quit smoking
[23]. Furthermore, that study also found that a group of
current smokers (42%) perceived that e-cigarettes was
not less harmful than tobacco cigarettes. Dawkins et al
also found that motivations for using e-cigarettes were
mixed [3]. Four in ten current smokers (40%) cited a de-
sire for a ‘partial alternative’to smoking as a reason for
using e-cigarettes, while 66% stated that they wanted a
‘complete alternative’, again suggesting that whilst most
use is quit-related, a substantial proportion is recreational.
Health effects
The advent and rapid uptake of e-cigarettes has spawned
a number of well-placed questions regarding their safety,
which include queries as to the toxicity of their refill
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fluids and of vapor, as well as their potential to cause
cancer or affect other organ systems beyond the lung.
Eight of the reviewed studies analyzed the health ef-
fects of e-cigarettes and two of those measured toxin
levels in the vapor. Both detected toxins in vapor, but at
levels which were either dramatically lower than those
found in tobacco cigarettes or clinically insignificant
[12,13]. Goniewicz et al. found that the vapor of all 12 e-
cigarette brands tested contained at least 9 of the 11
toxic substances measured. When compared to toxicity
levels known to be present in tobacco smoke, concentra-
tions of substances in e-cigarette vapor were dramatic-
ally lower in e-cigarettes. Levels of nitrosamines were
380-fold lower and acetaldehyde were 450-fold lower in
e-cigarettes than conventional tobacco cigarettes. Levels
of carcinogenic formaldehyde were only 9-fold lower in
e-cigarettes compared to tobacco cigarettes, which the
researchers deemed ‘comparable’to cigarette smoke
[12]. The other study looking at toxins in vapor was
funded in most part by the American National Vapers’
Club (a possible conflict of interest) also found the
vapor of all 4 brands tested contained at least 5 of the 7
toxic chemicals measured. However, levels of these sub-
stances were deemed to be clinically insignificant and
led to ‘no discernible health impacts’of the endpoints
investigated.
Neither study investigating the effects of e-cigarettes
on lung function suggested that they had any adverse ef-
fects [29,30]. The study by Flouris et al. found no degree
of airflow obstruction, as measured by FEV
1
/FVC ratio,
after both active and passive exposure to e-cigarette
vapor [30]. The other study found that smoking an e-
cigarette causes no airway obstruction, whereas cigarette
smoking causes mild airway obstruction and a small in-
crease in lung inflammation that lasts less than an hour
[29]. Conversely, a study by Vardavas et al found that
airway resistance and airway impedance increased
among a group of e-cigarette users compared with a
control group after 5 minutes of use, while the fraction
of expired nitrous oxide also declined in that group
compared to controls [31]. The fraction of expired ni-
trous oxide is important because it is implicated in the
pathophysiology of airways diseases associated with
smoking, and so lower expired levels imply higher re-
sidual levels in the airways to promote this pathogenesis.
Although those changes were statistically significant,
they only measured short-term parameters which were
not clinically significant [31].
There is conjecture within a limited body of research
regarding the cytotoxicity and cancer-causing ability of
e-cigarette refill solutions and vapor. One study, by Bahl
et al, showed some e-cigarette refill solutions to be ei-
ther moderately or highly cytotoxic to a variety of cell
types [32]. Embryonic and newborn stem cells were
found to be more sensitive to those cytotoxic effects than
differentiated adult fibroblasts, to a degree that researchers
deemed would be enough to cause embryonic loss or devel-
opmental defects in pregnancy [32]. Consistent with find-
ings in other studies of toxic substances in refill solutions,
those results were deemed not to be due to nicotine or hu-
mectant content, but rather were correlated with the variety
and concentrations of chemicals that flavor the solutions
[32].Contrarytothosefindings,astudybyRomagnaet
al showed that e-cigarette vapor was not cytotoxic [4].
However, that study was funded by an e-cigarette manu-
facturer to test its own products, making the results highly
questionable.
Smoking cessation
There are two key issues to assess with regard to smoking
cessation. Firstly, whether people are using e-cigarettes to
quit smoking, and secondly whether they are effective for
that purpose. As foreshadowed, it has already been estab-
lished that some e-cigarette use is recreational [17,33], but
a larger proportion of the users are inhaling with an
intention to quit smoking. Two studies reported the pro-
portion of users attempting to quit, which ranged from
60% to 76% [3,17]. Among those intending to quit smok-
ing, only very small numbers of participants claimed to be
using the devices as an alternative in settings where smok-
ing is banned [3,15,24].
All of the studies investigating e-cigarettes for smoking
cessation have demonstrated they may be effective both
in aiding quit attempts and reducing the number of ciga-
rettes smoked [3,9,17,18,28]. Two randomized controlled
trials (RCTs) demonstrated favorable quit rates among
users of nicotine-containing e-cigarettes when compared
to either placebo or other nicotine replacement therapies
(NRT) [9,28]. One RCT found that 11% participants
achieved abstinence from tobacco smoking at 12 months
using nicotine e-cigarettes compared to 4% participants
who used placebo; while the other RCT found that 7%
participants achieved complete abstinence at 6 months
compared to 6% participants using nicotine patches and
4% participants with placebo devices. In one study, ab-
stinence was defined as complete self-reported abstin-
ence from tobacco smoking - not even a puff - together
with an exhaled carbon monoxide (eCO) concentration
of ≤7 ppm [28]. In the other study, abstinence was de-
fined as self-reported abstinence over the whole six-
month follow-up period, allowing ≤5 cigarettes in total
and verified by an eCO of ≤10 ppm [9]. Two further on-
line, cross-sectional cohort studies also indicated an ef-
fective role of e-cigarettes for smoking cessation [3,18].
In one survey among the first-time e-cigarette buyers
intending to quit, 31% had abstained completely from
smoking at 6 months, while in the second study, 50% of
current smokers stated that e-cigarettes had ‘very much’
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helped them to quit while only 4% stated that it did not
help. Those are similar to findings of an earlier study by
Etter et al investigating similar endpoints [17]. Those
findings collectively demonstrate that when compared to
existing smoking cessation aids, e-cigarettes perform
comparably and may well have an effective role in smok-
ing cessation and tobacco harm reduction.
E-cigarettes have also been shown to help reducing the
number of cigarettes smoked by users who were unable
to quit completely, or who were not intending to quit
[17,18,28]. In one study, 23% of e-cigarette users reduced
the number of cigarettes they smoked by more than half
at 3 months [28]. In another study 67% claimed that
they had reduced the number of cigarettes per day to
some degree [18]. In the third study, 92% of former
smokers said that e-cigarettes helped them reducing
their daily cigarette consumption [17].
One of the controversial issues surrounding e-cigarettes’
effectiveness in smoking cessation is whether dual use of
the devices along with tobacco cigarettes helps attenuate a
nicotine addiction, or whether it only serves to perpetuate
it [9,18,28]. On the issue of dual use of e-cigarettes and
traditional cigarettes, Bullen et al found that smokers who
intended to quit smoking but relapsed and continued using
e-cigarettes had a significant reduction of tobacco cigarette
consumption, leading them to believe that, just as dual use
of nicotine replacement therapy and cigarettes is known to
promote subsequent quit attempts, e-cigarettes may fulfil
thesamerole[9].Anotherstudyfoundthatdualuseofthe
two products by smokers, not necessarily intending to quit,
resulted in a 31% abstinence rate at 6 months, suggesting
that e-cigarettes could indeed act to attenuate nicotine ad-
diction rather than perpetuate it [18]. On the other hand,
Caponnetto et al found that dual users of e-cigarettes and
tobacco who successfully quit were more likely to relapse,
whereas those using e-cigarettes exclusively were more
likely to remain abstinent [28]. Similarly, Lee et al found
that adolescents who tried to quit smoking were more
likely to use e-cigarettes but less likely to abstain entirely,
suggesting that even if the devices do not promote a
complete quit attempt, they may result in harm reduction
by reducing the number of cigarettes smoked [27].
Regulation
Regulatory authorities are in the process of reviewing the
limited evidence available on e-cigarettes in order to make
decisions on legislation, which will strongly influence the
development of the e-cigarette market. In the US, the
Food and Drug Administration (FDA) attempted initially
to regulate e-cigarettes as drug-delivery devices [34]. How-
ever, this was blocked by lawmakers because the products
made no therapeutic claim, arguing they should instead be
regulated as tobacco products because they contained
tobacco-derived nicotine [15]. Consequently, the FDA is
now planning to regulate e-cigarettes as tobacco products,
with limitations on online sales, sales to minors and adver-
tising as well as imposing manufacturing quality control
standards. The FDA released an amended rule encom-
passing e-cigarettes for public comment in Autumn 2013.
During that period of regulatory wrangling, the absence of
limitations facilitated e-cigarette companies to become a
$2 billion industry in US [6].
The issue of the source of nicotine was raised in that de-
bate because synthetic and tobacco plant-derived nicotine
are treated differently from a legal perspective. Using the
example of the US, products containing synthetic nicotine
are either regulated as pharmaceutical products (and thus
subject to the same standards required for therapeutic drug
approval), or banned from the market if these standards are
not met. On the other hand, products containing tobacco
plant-derived nicotine and making no therapeutic
claim are regulated as tobacco products and subject to
the same standards as tobacco cigarettes. This legal
nuance further complicates the regulatory debate
about e-cigarettes. Since the source of nicotine in the
devices is not always clear, this again emphasizes the
need for further research into the contents, safety and
manufacturing standards of e-cigarettes in order to
properly inform regulatory decisions [15].
Commentary on the regulation of e-cigarettes has
been underway in the US, Australia and Europe, where
two main schools of thought have emerged. A pro-
regulation group cites concerns including safety, a
potential role as bridging and gateway products, and
creating another income source for the tobacco indus-
try as reasons for stringent regulation, possibly as
therapeutic or drug-delivery devices [10,15,24,33,35].
One group of researchers argues that e-cigarettes have
a net negative public health impact because they have
not been shown to be better than NRT and pose signifi-
cant risks in terms of safety and bridging use [33]. They
also argue that smoking cessation aids such as NRT
have not created the current smoking cessation trend,
rather it has been well-organized government publicity
campaigns that have de-normalized and de-glamorized
smoking [33]. While this seems heavy handed, the argu-
ment pertaining to net public health impact is pertinent
given safety concerns and the prevalence of recreational
use [9].
Another point of contention for the pro-regulation
group is that e-cigarettes are yet another tobacco indus-
try marketing ploy. Rather than a strategy designed to
offset declining tobacco sales, public health researchers
argue e-cigarettes are a vehicle to addict future tobacco
consumers, as well as creating a new income stream in
the meantime. One in particular argues that by using e-
cigarettes in this way, the tobacco industry aims to neg-
ate the current cessation trend, re-glamorize tobacco
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and smoking, present nicotine as benign to younger
people and re-addict ex-smokers [10].
A less stringent approach is favored by a compromise-
regulation group, which argues that premature over-
regulation may extinguish a potentially beneficial product
before concerns over its harms have been validated or its
benefits disproven. These researchers contend that e-
cigarettes should instead be regulated as tobacco products,
subject to the same conditions regarding safety and
manufacturing standards, as well as laws regarding sales
to minors and advertising, and refute the arguments of
the pro-regulation researchers in a number of ways
[8,24,25,36].
It is argued that e-cigarettes are not a big tobacco mar-
keting ploy, and that on the contrary, laws banning nico-
tine products that aren’t tobacco or approved therapeutic
products actually protect the tobacco industry’s dominant
market position - a dominance that e-cigarettes may break
if they are not regulated out of the market [8]. Over-
regulation may also inhibit further product sophistication
and innovation, stunting consumer uptake and reducing
the potential of e-cigarettes as smoking cessation aid [24].
This group of researchers acknowledges that safety con-
cerns are legitimate, but argues there is not yet any firm
evidence to validate them, and consequently a great deal
more research is required. On the issue of e-cigarettes as
bridging and gateway products, it is conceded that aggres-
sive marketing from big tobacco and other manufacturers
may very well facilitate this type of undesirable uptake,
and as such they should be subject to the same regulations
as tobacco in terms of marketing and advertising [25].
Some of these sentiments may be hazardous, however,
particularly regarding safety whereby it is suggested an un-
tested product should be permitted to continue to prolif-
erate unchecked, rather than the status quo whereby a
new product is restricted until proven safe.
Reflecting the compromise-regulation approach, the
UK government has already approved legislation to have
all e-cigarettes regulated as medicines from 2016, with
smokers advised to use traditional nicotine replacement
therapies instead. Incongruously, this means that the to-
bacco companies, which already control a considerable
amount of e-cigarette production, may eventually supply
therapeutic products to the National Health Service
(NHS). Indeed, the tobacco industry already does this
with some NRT products, a situation which has been
criticized for leading to their influence in tobacco policy
decision-making by asserting itself as a producer of ther-
apeutics [37]. Regulatory developments in the EU have
progressed independently with a hybrid approach; in
February 2014, the European Parliament voted to regu-
late e-cigarettes as tobacco products but those claiming
therapeutic benefit as medicinal devices. This legislation
will include a restriction on purchase age to a minimum
of 18, close limitations on advertising and marketing in-
cluding health warnings on packaging and the imposition
of manufacturing standards [38]. Elsewhere, Brazil, Norway
and Singapore, have banned the products altogether [6].
In Australia, the regulatory process has not been sub-
ject to the same debate, because the Therapeutic Goods
Administration (TGA) essentially banned e-cigarettes at
the outset [39]. Legislative discussions have thus been
bypassed in favor of safety and control, presumably until
further evidence of their potential harms and/or benefits
becomes available. The TGA prohibits the importation,
supply and sale of goods claiming therapeutic benefit
that it has not approved, which applies to e-cigarettes
marketed as smoking cessation aids. To cover remaining
products, it also bans the sale of goods not containing
tobacco that are designed to resemble tobacco products,
whether the resemblance is in the product itself or its
packaging. However, anecdotal evidence suggests that e-
cigarettes with different flavors are easily available at dif-
ferent retail shops, even in $2 shops in Australia. That
warrants further investigation for effective implementa-
tion of the ban in reality.
Discussion
The most important finding of this review is that the
long term health effects of e-cigarettes are unknown.
The review further revealed that the substantial majority
of e-cigarette users are middle-aged, predominantly male
and current smokers. In one study, university students
using e-cigarettes were an exception to this trend in that
while nearly three quarters were former or current
smokers, 12% had not previously smoked compared to
other groups. However, there is some evidence of use
amongst young people and non-smokers. Reasons for
using e-cigarettes are mixed, with most people using
them as smoking cessation aids but a significant propor-
tion is using for recreational use. E-cigarettes have
demonstrated quit and reduction rates comparable to
existing NRTs, although results have been varied and
further studies are recommended. Their ability to miti-
gate withdrawal symptoms, lack of side effects and cap-
acity to closely simulate behavioral and handling process
of smoking tobacco cigarettes, appear to benefit users.
There is limited evidence to suggest that e-cigarettes are
acting as ‘gateway’products to introduce non-smokers to
smoking. However, there is lack of data on e-cigarette use
among adolescents and it is unknown whether the popu-
larity of e-cigarettes has increased in this group.
Evidence regarding the health effects of e-cigarette
use was mixed and warrants further investigations. At
present, the balance of findings favors the non-toxicity
of e-cigarettes’vapor and e-cigarette use was not found
to adversely affect lung function in the short term.
Toxic substances have been found in e-cigarettes but at
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far lower levels than in traditional cigarettes. However,
serious questions remain regarding their effect on im-
portant endpoints including cytotoxicity and long term
health effects. This limited amount of safety research
emphasizes the need for further investigation into the
health effects of e-cigarettes, particularly the long term
health effects.
Profiling users and usage patterns of e-cigarettes is an
important first step in investigating the e-cigarette
phenomenon and has major implications for public
health programs and regulatory agendas. For example,
evidence of use among people who have never smoked
and adolescents gives weight to the bridging and gate-
way product concepts argued by several public health
researchers [15,24]. These terms refer to the pheno-
mena of current smokers using e-cigarettes merely to
perpetuate their habit in settings where smoking has
been banned (bridging) and the initiation of nicotine
and tobacco addictions amongst people who have never
smoked (gateway) [15,24]. However the bridging product
may indeed help to reduce daily cigarette use, so should
not be viewed unfavorably. Apart from the very small
number of university students using e-cigarettes, who
never smoked before, e-cigarettes did not appear to be
acting as gateway products. The prevalence of recre-
ational use of e-cigarettes gives some credence to the ar-
gument of one public health expert that e-cigarettes may
be “re-glamorising”smoking amongst vulnerable popula-
tion groups [10,24].
E-cigarette’s potential as smoking cessation aids could
tip the risk-benefit ratio in their favor. If scientific evi-
dence proves that that they are effective in smoking cessa-
tion - and on the proviso that safety concerns are properly
addressed through further investigations - the public
health value of e-cigarettes may yet prove to be substan-
tial. One of the controversial issues surrounding e-
cigarettes’effectiveness in smoking cessation is whether
dual use of the devices along with tobacco cigarettes helps
attenuate a nicotine addiction, or whether it only serves to
perpetuate it [9,18,28]. Results relating to the dual use of
e-cigarettes and traditional cigarettes assisting in abstin-
ence and reduction in smoking have led some researchers
to conclude that, just as dual use of NRT and cigarettes is
known to promote subsequent quit attempts, e-cigarettes
may fulfil the same role. This also appears to suggest that
e-cigarettes may attenuate nicotine addiction rather than
perpetuate it [18].
The studies we reviewed which investigated e-cigarettes
for smoking cessation demonstrated that they could be ef-
fective in aiding quit attempts and reducing the number of
cigarettes smoked [3,9,17,18,28]. Variability in rates of
smoking cessation and reduction between studies may re-
flect differing levels of nicotine in e-cigarettes of different
brands and batches, as well as variability in the amount of
nicotine extracted by different users based on nuances of
usage technique [40]. The study by Goniewicz et al.
compared vapors of sixteen e-cigarette brands/models
which were chosen based on their popularity in Polish,
UK and US markets. Analyses showed that total nico-
tine in the vapor produced by a given series of puffs
varied from 0.5–15.4mg.Thestudyalsofoundthat,on
average, only 50-60% of the nicotine contained in each
cartridge was actually vaporized [40].
Several plausible explanations for e-cigarettes’apparent
effectiveness in aiding smoking cessation and reduction
have been elucidated [3,17,28]. First, they may mitigate
withdrawal symptoms, which is a highly valuable effect
given that overcoming withdrawal symptoms are known to
be centrally implicated in a smoker’s ability to achieve and
maintain abstinence [3]. Secondly, e-cigarettes have not at
this stage been associated with significant side effects
[3,31]. Thirdly, studies suggest that there may be a behav-
ioral component to the devices’apparent effectiveness in
aiding smoking cessation; physical handling and manipula-
tion of a similar device, and the ability to respond to condi-
tioned smoking cues, may be factors in attenuating craving
for tobacco cigarettes [17,28]. Studies found that when
comparing nicotine and non-nicotine e-cigarettes both
were equally effective in reducing tobacco cigarette con-
sumption though those with nicotine performed better in
terms of attenuating withdrawal symptoms, reinforcing the
likelihood that this behavioral component may be a signifi-
cant factor [17,28].
E-cigarettes may, therefore, be able to either perpetuate
or attenuate nicotine addiction, depending on whether
users are motivated to quit or just use them recreationally
[14,21,23,35]. E-cigarettes may be an effective smoking
cessation aid for those intending to quit smoking but
also be used as bridging products which perpetuate
users’addiction to tobacco. It is this aspect of e-cigarette
use that is of growing concern from a public health per-
spective and has serious implications for the regulation of
e-cigarettes [10,24,36].
Findings from this review regarding user profiles and ef-
fectiveness as cessation aids should be used to inform
regulatory decisions determining the future of e-cigarettes.
Current debate about their regulation falls into two para-
digms. One argues for strict regulation, similar to the way
therapeutic products are governed. The other puts for-
ward a compromised approach that ensures users’safety
while permitting commercial availability and ongoing
product sophistication while their potential harms and
benefits are further investigated [8,10]. The argument for
compromised regulation is based on the assumption that
e-cigarettes currently have a net positive public health im-
pact [8]. Given that some e-cigarette use is recreational
and safety concerns persist, it can be argued that
e-cigarettes do not yet have a net positive public health
Rahman et al. Tobacco Induced Diseases 2014, 12:21 Page 7 of 9
http://www.tobaccoinduceddiseases.com/content/12/1/21
impact. It is possible that e-cigarettes are initiating or per-
petuating more nicotine addictions than they are attenuat-
ing. Therefore, a regulatory agenda which controls those
negative use trends while permitting use for cessation, ap-
pears to make sense. Regulation then needs to control the
drivers of negative use (i.e. non-quit related recreational
use), such as low cost, widespread availability and unfet-
tered marketing [9,12,13,25]. Since sales of e-cigarettes
have been shown to be sensitive to price changes, policies
increasing e-cigarette retail prices (such as limiting re-
bates, discounts and coupons and imposing tax on e-
cigarettes), could potentially lead to significant reductions
in e-cigarette sales [41].
Currently e-cigarettes are thought to be more expensive
than tobacco in developing countries and so are viewed as
more of a luxury product [42]. Two scenarios cause con-
cern in this setting. Firstly, if e-cigarettes are shown to act
as gateway products and their prices subsequently rise,
they may promote further tobacco smoking initiation once
e-cigarettes become unaffordable, as research shows price
is a key factor in tobacco product initiation in developing
countries [43]. Secondly, if e-cigarettes are shown to be
safe alternatives to smoking that do not promote subse-
quent tobacco cigarette use, their higher prices may act as
a disincentive for tobacco smokers to switch to a safer al-
ternative. However, these are speculative scenarios and
only highlight the need for further investigation into the
use of the devices and pricing in developing countries.
Limitations
Similar to other narrative reviews, this review had a num-
ber of limitations. Studies were selected to provide a com-
prehensive overview on the issues relating to e-cigarettes
focusing on our objectives. As it was not a systematic re-
view paper, it is possible that some key studies have been
missed and selection biasness cannot be avoided. We tried
to minimize these issues by following a specific search
strategy unlike other narrative reviews. Quality of the se-
lected studies was not assessed as that was beyond the
scope of the review.
Conclusions
Our overview of the literature on e-cigarettes has illumi-
nated key areas of interest including their patterns of
use, health effects, effectiveness for smoking cessation
and regulatory issues. The cytotoxicity and long term
health effects of e-cigarettes are unknown. Nevertheless
the e-cigarette market continues to expand, largely
driven by middle-aged smokers who claim to be using e-
cigarettes in an attempt to reduce or quit smoking. E-
cigarettes may have some potential as smoking cessation
aids and, in the researchers’view, should therefore be
subject to further research and regulation similar to
other nicotine replacement therapies.
Abbreviations
E-cigarettes: Electronic cigarettes; NRT: Nicotine replacement therapy;
FDA: United States Food and Drug Administration; TGA: Australian Government
Therapeutic Goods Administration.
Competing interests
The authors declare that they have no competing interests.
Authors’contributions
MAR and LWC were involved in conception of the project. MAR led the design
of the study, provided guidance to NH for searching literature. MAR and NH
conducted the reviews and analyzed the data. MAR, NH and LWC were
involved in early drafts of the manuscript. MAR, AW and LWC critically reviewed
the manuscript. All authors read and approved the final manuscript.
Authors’information
MAR is a public health specialist and a physician, who is working as a Senior
Research Fellow at The Cardiovascular Research Centre (CvRC) and St
Vincent’s Centre for Nursing Research (SVCNR), Australian Catholic University
Melbourne. He has a strong track record on tobacco research, both in
developed and developing countries, specifically focusing on epidemiology.
NH is a final year MD student from the University of Melbourne and worked
at CvRC on this project as part of his ‘scholarly selective’research project
component of his course. AW is a cardiologist at St Vincent’s Hospital
Melbourne, and Principal Research Fellow & Reader, Department of Medicine
at the University of Melbourne. LWC is Professor of cardiovascular nursing
and Director of CvRC and SVCNR. She is a nurse and clinical health
researcher with over 20 years’experience in cardiovascular health and
research. Her other research expertise includes women and cardiovascular
disease, cardiovascular risk assessment and prevention, as well as models of
care around cardiovascular diseases.
Author details
1
St Vincent’s Centre for Nursing Research (SVCNR), Australian Catholic
University, Melbourne, Australia.
2
The Cardiovascular Research Centre (CvRC),
Australian Catholic University, Melbourne, Australia.
3
The University of
Melbourne, Melbourne, Australia.
4
St Vincent’s Hospital, Melbourne, Australia.
Received: 1 April 2014 Accepted: 27 October 2014
Published: 15 December 2014
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Cite this article as: Rahman et al.:Electronic cigarettes: patterns of use,
health effects, use in smoking cessation and regulatory issues. Tobacco
Induced Diseases 2014 12:21.
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