Electronic cigarettes – a summary of evidence and expert opinion
What are electronic cigarettes? (also known asvapes,MODs, vapours, e-cigs, cig-a-likes, e-cigarettes, and ENDS (Electronic Nicotine Delivery Systems)) (WHO, 2009; Yamin etal, 2010; AliDresler, 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 byburning 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 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 healthcampaigning 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 touse 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% in2014 (figure 1). There has also been a gradual but consistent rise in the number of current smokers whoalso 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 that95% of smokers and 90% of non-smokers had heard of electronic cigarettes. Regular use of thedevices 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 havingever tried an electronic cigarette and virtually none continuing use. Among former smokers, 11.8% had triedelectronic cigarettes but only 4.7% use them regularly.
Figure 1: Electronic cigarette use among current adult cigarette smokersin Great Britain (2010-2014)(Reproduced from Ash Use of electronic cigarettes in Great Britain (July 2014): )(Ash, 2014a)In 2013, two thirds of 11-18 year olds and 83% of 16-18 year olds had heard of electroniccigarettes.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 thosewho had heard of electronic cigarettes, 7% (10% among 16-18 year olds) had triedelectronic 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), 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, non-medical 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 smokeridentity but without the risk of smoke.They are also relatively inexpensive, and althoughstart-up costs can behigh, 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): )(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(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 isthe addictive substance in traditional tobacco cigarettes (Britton & Bogdanovica, 2014).
There are three key elements that influence nicotine delivery from anelectronic cigarette (Goniewiczet al, 2013; BrittonBogdanovica, 2014):
- vapour to human body: the nicotine content in the cartridge, which determines the amount of nicotine vapourised;
- the efficacy of vaporization, which affects levels of nicotine transferred from a cartridge into aerosol; and
- 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 intoboth the systemic venous circulation from the oropharynx and large airways, and thepulmonary circulation from the small airways and alveoli. The latter route of absorptiongenerates a rapid peak in systemic arterial nicotine levels and hence rapid delivery tothe brain (Benowitzet al, 2010). No other nicotine product has yet been able to demonstratemimicking the speedand high dose delivery characteristics of cigarettes. Since nicotine absorbed from theintestine is heavily metabolised on first pass through of the liver, conventional nicotinereplacement therapy (NRT) products rely on venous absorption from skin, nose ormouth, 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 thatis sufficiently fine to reach the alveoli, but available pharmacokinetic data suggests thatabsorption is primarilyfrom the upper airway, that is, slower than a cigarette, andachieving systemic venous blood levels of similar order of magnitude to a conventionalNRT inhalator (Bullenet al, 2010).Data on the arterial nicotine levels achieved by electronic cigarettes isnot 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 between use of electronic cigarettes and smoking, concerns about re-normalisation 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 fromminor and transient adverse effects at the point of absorption, nicotine is not asignificant health hazard. Nicotine does not cause serious adverse health effects suchas acute cardiac events, coronary heart disease or cerebrovascular disease (Hubbard et al, 2005; NICE, 2013) andis not carcinogenic(IARC, 2012). The doses of nicotine delivered by electronic cigarettes aretherefore extremely unlikely to cause significant short or long-term adverse events. Cigarettes deliver nicotine in conjunction with a wide range of carcinogens and othertoxins contained in tar, including nitrosamines, acetone, acetylene, DDT, lead,radioactive polonium, hydrogen cyanide, methanol, arsenic and cadmium, (Eriksen, et al, accessed 2014) andvapour phase toxins such as carbon monoxide (RCP, 2000). In contrast, electronic cigarettes donot burn tobacco, so any toxins in vapour arise either from constituents andcontaminants of the nicotine solution, and products of heating to generate vapour. Theprincipal component other than nicotine is usually propylene glycol, which is not knownto have adverse effects on the lung (USEPA, 2006) but has not been tested inmodels that approximate the repeated inhalation, sustained over many years thatelectronic cigarette use would involve. Two cases of lipoid pneumonia attributedto inhalation of electronic cigarette vapour have been published, one in the peer-review literature (McCauleyet al, 2012) the othera news report (BBC News).
Despite some manufacturers’ claims that electronic cigarettes are harmless there isalso evidence that electronic cigarettes contain toxic substances, including smallamounts of formaldehyde and acetaldehyde, which are carcinogenic to humans (Goniewiczet al, 2013a) andthat in some cases vapour contains traces of carcinogenic nitrosamines, and sometoxic metals such as cadmium, nickel and lead (Goniewiczet al, 2013a). Although levels of these substancesare much lower than those in conventional cigarettes,(Goniewiczet al, 2013a)regular exposure over manyyears is likely to present some degree of health hazard, though the magnitude of thiseffect is difficult to estimate.
Relation to smoking
There have been some suggestions that among non-smokers, particularly children and young people, electronic cigarettesmight be used as a gateway to smoking and promote smoking uptake and nicotineaddiction (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 whomight otherwise have quit smoking completely, representing missed opportunities toachieve 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 ismore 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 cigarettesmoking, in places where smoking is currently prohibited might re-normalise smokingand undermine tobacco control efforts (Fairchildet 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 safetyregulations which do not impose specific standards of purity or efficacy, and controladvertising 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,through pre-screening. Proponents of this approach maintain that it minimisesregulatory barriers and costs of product development and innovation, and that freedomto advertise maximises reach across the smoking population. Opponents hold thatgeneral product regulation does not ensure that products deliver nicotine reliably orwithout unnecessary and potentially hazardous components or contaminants, andallows 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 thatfrom 2016, it intended to regulate electronic cigarettes and other nicotine-containingproducts as medicines by function, and thus require manufacture to medicinal purityand delivery standards, and proactive controls on advertising (CAP, 2014). The proposedregulation (MHRA, 2014), described as ‘right touch’, is intended to provide a relatively streamlinedroute to licensing, particularly by deeming any nicotine device that is proved to delivernicotine to be effective as a smoking substitute or cessation aid, thus obviating theneed for expensive clinical trials. Manufacturing to medicines standards does howeverrepresent a challenge and inevitably increases costs. On the positive side however,licensed NRT products currently enjoy a preferential 5% VAT rate, which to someextent offsets these additional costs, and will benefit from being prescribable on NHSprescriptions in the UK. Proponents of this approach welcome the quality and deliverystandards imposed, and the advertising controls which should prevent marketingabuses before rather than after the event. Opponents argue that this level of regulationwill stifle innovation and delay development of innovative products that could savelives.These MHRA proposals were published before the revision of the EU TobaccoProducts Directive in 2014 (EU, 2014), one consequence of which is to close offthe option of deeming all nicotine products as medicines by function. MHRA regulationwill therefore no longer be obligatory in the UK from 2016, but option of applying for amedicines licence remains open.
What other countries are doing about electronic cigarettes
In March 2014 the European Parliament and Council moved to end marketing undergeneral product safety regulations under the terms of the new Tobacco ProductDirective (TPD) (EU, 2014). Under this directive, advertising of nicotine-containing devices thatare not licensed as medicines will be prohibited, products will be required to carryhealth 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, andsuppliers will be required to bear full responsibility for quality and safety when used‘under normal or reasonably foreseeable conditions’ (EU, 2014). Dates for enactment are yet tobe specified, but legislation is expected to be required in member states by 2016, andfull compliance by 2017. In practice, this means that from 2017 at the latest, supplierswill have to choose between the probably lower manufacturing costs but greatermarketing restrictions imposed by the TPD, or to accept the higher manufacturing costsbut 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).
References
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Britton, J and Bogdanovica, I. (2014). Electronic cigarettes; A report commissioned by Public Health England. UKCTAS/The University of Nottingham. Available from: [accessed 17.09.2014]
Bullen, C. et al. (2010). Effectofanelectronicnicotinedeliverydevice(ecigarette)ondesiretosmokeandwithdrawal,userpreferencesandnicotinedelivery:randomisedcross-overtrial.TobaccoControl, (2):p.98-103.
CADTH (Canadian Agency for Drug and Technologies in Health), 2012.Electronic Cigarettes: A Review of the Clinical Evidence and Safety. Available from: [18.09.2013]
Cameron, JM, Howell, DN, White, JR, Andrenyak, DM, Layton, ME, & Roll, JM.(2014). Variable and potentially fatal amounts of nicotine in e-cigarette solutions.Tobacco Control. 23: 77-78.