Electronic cigarettes – a summary of evidence and expert opinion
What are electronic cigarettes? (also known as vapes, MODs, vapours, e-cigs,
cig-a-likes, e-cigarettes, and ENDS (Electronic Nicotine Delivery Systems))
(WHO, 2009; Yamin et al, 2010; Ali & Dresler, 2011; Britton & Bogdanovica; 2014).
Electronic cigarettes were invented in China in 2003, first coming to Europe
in 2005 and have become increasingly popular since.
The term electronic cigarette is a
generic term and not very accurate
since, despite their name, they are
totally different from cigarettes.
Many, but not all, are in the form
of thin white tubes that look like
cigarettes (cig-a-likes; right, and
below). Some electronic cigarettes
contain nicotine, others do not.
Some produce a white odourless
vapour, while others produce no vapour at all. Some have additional flavours
such as chocolate, menthol, gummy bear, tobacco etc.
They do not burn tobacco
and do not create smoke,
therefore are not products of
combustion, like traditional
cigarettes. As electronic
cigarettes producing nicotine
vapour from a solution
rather than by burning
tobacco means that
electronic cigarette vapour is free from almost all of the many toxic
chemicals that accompany nicotine in traditional cigarette smoke.
Electronic cigarettes are either rechargeable or disposable. Both versions
have a cartridge with liquid and built-in atomizer with a membrane to
suspend ingredients, liquid containing water, flavouring (various), nicotine
(some), and propylene glycol (preservative), a battery, some have a LED tip
that lights up when the user inhales on the device, and others may have
additional additives depending on the product and manufacturer. Disposable
ones also sometimes have a paper-wrap texture, to mimic cigarettes.
Rechargeable devices additionally tend to have removable cartridges that
screw on to the battery. The batteries tend to last for a day or two, and are
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rechargeable in a few hours. When users inhale on the electronic cigarette,
the liquid in the cartridge heats so that some of it evaporates, producing a
vapour. For those electronic cigarettes that contain nicotine, it is this vapour
that delivers the nicotine into the user's lungs. There is no smoke, but some
electronic cigarettes release a vapour into the surrounding air as the user
exhales, mimicking smoke.
Newer versions, sometimes known as
second or third generation electronic
cigarettes (example shown in picture
right), look less like cigarettes but
work in a similar manner to other
electronic cigarettes on the market.
Electronic cigarette use
Action on Smoking and Health (ASH), a national public health campaigning
charity that aims to eliminate the harm caused by tobacco (ASH, 2014),
commissioned a series of surveys (via YouGov) on electronic cigarette use
starting in 2010 (YGS1) with a survey of adult smokers. Questions about
electronic cigarettes were extended to include all adults in surveys conducted
in February 2012 (YGS2) 2013 (YGS3) and March 2014 (YGS4). In March
2013 (YGS5) an additional survey of children aged 11 to 18 was conducted.
From these surveys ASH estimates that there are currently about 2.1 million
adults in Great Britain using electronic cigarettes, of these, approximately
700,000 are ex-smokers while 1.3 million continue to use tobacco alongside
their electronic cigarette use (sometimes referred to as duel users).
Since 2010, the number of electronic cigarette users has continued to rise. In
2010, only 8.2% of current smokers had ever tried electronic cigarettes,
rising to 50.6% in 2014 (figure 1). There has also been a gradual but
consistent rise in the number of current smokers who also use electronic
cigarettes on a regular basis, from 2.7% in 2010 to 17.6% in 2014 (figure
1).
Awareness of electronic cigarettes is widespread among adults. The 2014
survey found that 95% of smokers and 90% of non-smokers had heard of
electronic cigarettes. Regular use of the devices is predominantly confined to
current and ex-smokers. The 2014 survey found electronic cigarette use
among never smokers to be negligible with less than 1% of never smokers
having ever tried an electronic cigarette and virtually none continuing use.
Among former smokers, 11.8% had tried electronic cigarettes but only 4.7%
use them regularly.
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Figure 1: Electronic cigarette use among current adult cigarette
smokers in Great Britain (2010-2014) (Reproduced from Ash Use of electronic
cigarettes in Great Britain (July 2014): http://www.ash.org.uk/files/documents/ASH_891.pdf )(Ash, 2014a)
In 2013, two thirds of 11-18 year olds and 83% of 16-18 year olds had
heard of electronic cigarettes. Among children who have heard of electronic
cigarettes, sustained use is not common and generally confined to children
who currently or have previously smoked. Of those who had heard of
electronic cigarettes, 7% (10% among 16-18 year olds) had tried electronic
cigarettes at least once, and 2% reported using them monthly or weekly.
Among the 7% of children who reported some use of electronic cigarettes,
only 28% had used them in the last month. Of those who had never smoked
a cigarette, 99% reported never having tried electronic cigarettes and 1%
reported having tried them “once or twice”. A further youth survey by ASH
(YGS6; 2014) has found that overall the number of young people who have
ever tried an electronic cigarette has increased by 3%, from 7% in 2013 to
10% in 2014.
Why are they increasingly popular?
The surveys conducted by Ash (2014a) indicated that the main reasons for
electronic cigarette use as reported by adult electronic cigarette users were
to completely, or partially, replace traditional tobacco cigarette smoking (see
figure 2). Although existing versions of electronic cigarettes currently on the
market are thought to be no more effective at nicotine delivery than existing
regulated and licensed Nicotine Replacement Therapies (NRT)(see below),
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there is potential that as these products evolve and develop this may
change. Unlike traditional NRT products, their availability in convenience
stores and supermarkets, their cig-a-like look, competitive pricing, nonmedical image, and social acceptability also probably contribute to their
recent increase in popularity and use. Electronic cigarettes offer nicotine
delivery in a format that closely mimics smoking which enables users to
retain their smoker identity but without the risk of smoke. They are also
relatively inexpensive, and although start-up costs can be high, running costs
are much lower than smoking.
Figure 2: Reported reasons for adult electronic cigarette use
(Reproduced
from Ash Use of electronic cigarettes in Great Britain (July 2014):
http://www.ash.org.uk/files/documents/ASH_891.pdf )(Ash, 2014a)
What is known about them?
Nicotine content, delivery and pharmacokinetics
In 2012 the Canadian Agency for Drug and Technologies in Health (CADTH)
conducted a literature review and found that there was some evidence,
although it was of low level that showed electronic cigarette use can reduce
the desire to smoke (CADTH, 2012). Evidence on the content and
emission of electronic cigarettes is limited. If electronic cigarettes are to
be used as a less harmful replacement or alternative to traditional cigarettes
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(the reason they were first invented), then they need to be able to effectively
deliver nicotine to the user, and in a manner that is less harmful than
traditional cigarettes to the user and/or others around them, as nicotine is
the addictive substance in traditional tobacco cigarettes (Britton &
Bogdanovica, 2014).
There are three key elements that influence nicotine delivery from an
electronic cigarette (Goniewicz et al, 2013; Britton & Bogdanovica, 2014):
1. vapour to human body: the nicotine content in the cartridge, which
determines the amount of nicotine vapourised;
2. the efficacy of vaporization, which affects levels of nicotine transferred
from a cartridge into aerosol; and
3. the bioavailability of nicotine, which determines the dose and speed of
absorption of nicotine from the aerosol and subsequent transfer into
the blood stream and hence to nicotine receptors in the brain.
All of these characteristics vary across brands, manufacturers, and
product designs; there is not any standardisation. Smoking a cigarette
delivers nicotine throughout the lung and leads to absorption into both the
systemic venous circulation from the oropharynx and large airways, and the
pulmonary circulation from the small airways and alveoli. The latter route of
absorption generates a rapid peak in systemic arterial nicotine levels and
hence rapid delivery to the brain (Benowitz et al, 2010). No other nicotine
product has yet been able to demonstrate mimicking the speed and high
dose delivery characteristics of cigarettes. Since nicotine absorbed from the
intestine is heavily metabolised on first pass through of the liver,
conventional nicotine replacement therapy (NRT) products rely on venous
absorption from skin, nose or mouth, which avoid this hepatic metabolism
but produce relatively low plasma levels, relatively slowly (Henningfield,
1995). It is not yet clear whether electronic cigarettes produce vapour that is
sufficiently fine to reach the alveoli, but available pharmacokinetic data
suggests that absorption is primarily from the upper airway, that is, slower
than a cigarette, and achieving systemic venous blood levels of similar order
of magnitude to a conventional NRT inhalator (Bullen et al, 2010). Data on
the arterial nicotine levels achieved by electronic cigarettes is not
available.
Concerns about electronic cigarettes
As use of electronic cigarettes is a relatively recent phenomenon and
evidence to date is scarce, there are still some major concerns about
these products: those related to product itself, those about the relation
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between use of electronic cigarettes and smoking, concerns about renormalisation of smoking, as well as the regulation of electronic cigarettes.
The content of electronic cigarettes
The addictive component of tobacco smoke is nicotine (RCP, 2000). However,
aside from minor and transient adverse effects at the point of absorption,
nicotine is not a significant health hazard. Nicotine does not cause serious
adverse health effects such as acute cardiac events, coronary heart disease
or cerebrovascular disease (Hubbard et al, 2005; NICE, 2013) and is not
carcinogenic (IARC, 2012). The doses of nicotine delivered by electronic
cigarettes are therefore extremely unlikely to cause significant short or longterm adverse events. Cigarettes deliver nicotine in conjunction with a wide
range of carcinogens and other toxins contained in tar, including
nitrosamines, acetone, acetylene, DDT, lead, radioactive polonium, hydrogen
cyanide, methanol, arsenic and cadmium, (Eriksen, et al, accessed 2014)
and vapour phase toxins such as carbon monoxide (RCP, 2000). In contrast,
electronic cigarettes do not burn tobacco, so any toxins in vapour arise either
from constituents and contaminants of the nicotine solution, and products of
heating to generate vapour. The principal component other than nicotine is
usually propylene glycol, which is not known to have adverse effects on the
lung (USEPA, 2006) but has not been tested in models that
approximate the repeated inhalation, sustained over many years that
electronic cigarette use would involve. Two cases of lipoid pneumonia
attributed to inhalation of electronic cigarette vapour have been published,
one in the peer-review literature (McCauley et al, 2012) the other a news
report (BBC News).
Despite some manufacturers’ claims that electronic cigarettes are harmless
there is also evidence that electronic cigarettes contain toxic substances,
including small amounts of formaldehyde and acetaldehyde, which are
carcinogenic to humans (Goniewicz et al, 2013a) and that in some cases
vapour contains traces of carcinogenic nitrosamines, and some toxic metals
such as cadmium, nickel and lead (Goniewicz et al, 2013a). Although levels
of these substances are much lower than those in conventional cigarettes,
(Goniewicz et al, 2013a) regular exposure over many years is likely to
present some degree of health hazard, though the magnitude of this
effect is difficult to estimate.
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Relation to smoking
There have been some suggestions that among non-smokers, particularly
children and young people, electronic cigarettes might be used as a gateway
to smoking and promote smoking uptake and nicotine addiction (Cameron,
2014). Also that electronic cigarettes could re-normalise smoking and
undermine the de-normalisation of smoking that has happened in the UK
over recent decades, particularly the smoke free legislation. Although
electronic cigarette use among children and young people remains low, in
recent years it has been increasing. As yet we do not have evidence to
support or refute these claims.
It has additionally been suggested that there is a risk of sustained dual use
among smokers who might otherwise have quit smoking completely,
representing missed opportunities to achieve the health gains achievable
from complete cessation. Recent figures have shown that less smokers are
accessing stop smoking services nationally (HSCIC, 2013) as well as locally
(Camquit data), but to know for sure why this is more research is
required. These devices could dilute or divert attention from other more
evidence-based strategies (such as complete abstinence). Also, there are
concerns that ex-smokers could take up the new products with some
relapsing to smoking, but currently there is insufficient evidence to
determine if this is the case, or not.
Some argue the use of electronic cigarettes, which to a degree resembles
cigarette smoking, in places where smoking is currently prohibited might renormalise smoking and undermine tobacco control efforts (Fairchild et al,
2013). But as of yet there is not sufficient evidence to determine if this is
the case, or not.
Finally, there are concerns over the involvement of the tobacco industry in
the development, promotion and distribution of these products, that the
tobacco industry is continuing to profit from addiction and that they will use
brand stretching to draw people in to non-tobacco products and then on to
cigarettes. The dangers of these products are currently unknown and
could be underestimated.
Electronic cigarette regulation in the UK
Current UK regulation means electronic cigarettes are currently marketed
under general product safety regulations which do not impose specific
standards of purity or efficacy, and control advertising through voluntary
codes of practice (CAP, 2014), which is under review (CAP, 2014a) but deal
with breaches reactively, in response to complaints, rather than proactively,
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through pre-screening. Proponents of this approach maintain that it
minimises regulatory barriers and costs of product development and
innovation, and that freedom to advertise maximises reach across the
smoking population. Opponents hold that general product regulation does not
ensure that products deliver nicotine reliably or without unnecessary and
potentially hazardous components or contaminants, and allows inappropriate
marketing, for example, to children or to non-smoking adults.
In 2013, after a consultation process that began in 2010, the UK MHRA (UK
medicines and medical devices regulatory body) announced that from 2016,
it intended to regulate electronic cigarettes and other nicotine-containing
products as medicines by function, and thus require manufacture to
medicinal purity and delivery standards, and proactive controls on
advertising (CAP, 2014). The proposed regulation (MHRA, 2014), described
as ‘right touch’, is intended to provide a relatively streamlined route to
licensing, particularly by deeming any nicotine device that is proved to
deliver nicotine to be effective as a smoking substitute or cessation aid, thus
obviating the need for expensive clinical trials. Manufacturing to medicines
standards does however represent a challenge and inevitably increases costs.
On the positive side however, licensed NRT products currently enjoy a
preferential 5% VAT rate, which to some extent offsets these additional
costs, and will benefit from being prescribable on NHS prescriptions in the
UK. Proponents of this approach welcome the quality and delivery standards
imposed, and the advertising controls which should prevent marketing
abuses before rather than after the event. Opponents argue that this level of
regulation will stifle innovation and delay development of innovative products
that could save lives. These MHRA proposals were published before the
revision of the EU Tobacco Products Directive in 2014 (EU, 2014), one
consequence of which is to close off the option of deeming all nicotine
products as medicines by function. MHRA regulation will therefore no longer
be obligatory in the UK from 2016, but option of applying for a medicines
licence remains open.
What other countries are doing about electronic cigarettes
In March 2014 the European Parliament and Council moved to end marketing
under general product safety regulations under the terms of the new Tobacco
Product Directive (TPD) (EU, 2014). Under this directive, advertising of
nicotine-containing devices that are not licensed as medicines will be
prohibited, products will be required to carry health warnings, meet purity
and emissions standards that are yet to be defined, provide data on nicotine
uptake, be subject to restrictions on total nicotine content, and suppliers will
be required to bear full responsibility for quality and safety when used ‘under
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normal or reasonably foreseeable conditions’ (EU, 2014). Dates for
enactment are yet to be specified, but legislation is expected to be required
in member states by 2016, and full compliance by 2017. In practice, this
means that from 2017 at the latest, suppliers will have to choose between
the probably lower manufacturing costs but greater marketing restrictions
imposed by the TPD, or to accept the higher manufacturing costs but other
benefits of medicines licensing.
Non-E.U.
Both US Food and Drug Administration (FDA, 2009; FDA, 2011) and Health
Canada (Health Canada, 2009) have issued warnings of the health risks
posed by electronic cigarettes. Because of the lack of data about their safety
and efficacy, electronic cigarettes have been banned in Australia, Canada,
Singapore and Brazil (WHO, 2009; Ali & Dresler, 2011).
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YGS1 (YouGov survey). Total sample size was 12,597 adults. Fieldwork was
undertaken between 17th and 22nd March 2010 All surveys were carried out
online. All figures have been weighted and are representative of GB adults
(aged 18+) or children (11 to 18) as appropriate. (Results reported in
http://www.ash.org.uk/files/documents/ASH_891.pdf) [accessed
19.09.2014]
YGS2 (YouGov survey). Total sample size was 12,436 adults. Fieldwork was
undertaken between 27th February and 16th March 2012. (Results reported
in http://www.ash.org.uk/files/documents/ASH_891.pdf) [accessed
19.09.2014]
YGS3 (YouGov survey). Total sample size was 12,171 adults. Fieldwork was
undertaken between 1st and 19th February 2013. (Results reported in
http://www.ash.org.uk/files/documents/ASH_891.pdf) [accessed
19.09.2014]
YGS4 (YouGov survey). Total sample size was 12,269. Fieldwork was
undertaken between 5th and 14th March 2014. All surveys were carried out
online. The figures have been weighted and are representative of all GB
Adults (aged 18+).(Results reported in
http://www.ash.org.uk/files/documents/ASH_891.pdf) [accessed
19.09.2014]
YGS5 (YouGov survey). Total sample size was 2,178 children aged 11 to 18.
Fieldwork was undertaken 21st - 28th March 2013. (Results reported in
http://www.ash.org.uk/files/documents/ASH_891.pdf) [accessed
19.09.2014]
YGS6 (YouGov Survey). The research was conducted by YouGov as part of
the ASH Smokefree Youth survey, however the figures within this release are
based on further analysis conducted by Public Health England. The full
analysis is being prepared for peer reviewed publication and will be published
in due course. Fieldwork was conducted by YouGov between 21st March and
1st April 2014. [currently unpublished, received by personal communication]
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