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The growingly popular electronic cigarettes are one form of “Electronic nicotine delivery systems”, or “ENDS”. They use a heating element to heat a solution that is vaporized and then delivered to the user in the form of an aerosol, which can be inhaled. The main constituents of this solution are propylene glycol and flavoring agents, in addition to nicotine, which is not always present.
Electronic nicotine delivery systems are the subject of a public health debate among tobacco-control advocates that has become more divisive as their use has increased. Whereas some experts welcome ENDS as a pathway to the reduction of tobacco smoking, others characterize them as products that could undermine efforts to denormalize tobacco use. ENDS, therefore, represent an evolving frontier, filled with promise and threat, for tobacco control.
Some electronic nicotine delivery systems are shaped to look like their conventional tobacco counterparts (e.g. cigarettes, cigars, cigarillos, pipes, or hookahs), they also take other shapes, and can look like other everyday items such as pens, USB memory sticks, and larger cylindrical or rectangular devices. There is considerable variation (battery voltage, circuitry differences) from one type of device to another in the products’ ability to heat the solution to an aerosol, which may, on the one hand affect delivery of nicotine and other constituents, and on the other hand, contribute to the formation of toxicants in the emissions. Under near real-use conditions, e-cigarettes increased indoor air levels of polycyclic aromatic hydrocarbons, 1,2-propanediol, 1,2,3-propanetriol, glycerine, and aluminium.
The way the devices are used may affect nicotine absorption: length of puffs, depth of inhalation and frequency of use may be factors. In addition some users modify products at home to alter delivery of nicotine and/or other drugs. Products vary widely in the ease with which they can be modified and the ease with which they can be filled with substances other than nicotine solutions.
The market seems to be booming. It is estimated that in 2014 there were 466 brands and that in 2013 US$ 3 billion was spent on ENDS globally. Sales are forecasted to increase by a factor of 17 by 2030. In 2012, 7% of EU citizens aged 15 years and over had tried electronic cigarettes. However, only 1% of the total population used them regularly. In 2013, 47% of smokers and ex-smokers in the United States of America had tried e-cigarettes, but prevalence of established use was 4% in this group. Users report that the main reasons for using ENDS are to reduce or stop smoking and because they can be used in smoke-free places.
Most ENDS products have not been tested by independent scientists, but the limited testing has revealed wide variations in the nature and toxicity of contents and emissions.
The existing evidence shows that ENDS aerosol is not merely “water vapour” as is often claimed in the marketing for these products. ENDS use poses serious threats to adolescents and fetuses.
Health risks from nicotine inhalation are mainly, but not only, affected by how much nicotine is delivered to the user. Nicotine is addictive, and can contribute to cardiovascular disease. It can have adverse effect during pregnancy, and although it does not cause cancer by itself, it can function as a ‘cancer promoter’.
The evidence is sufficient to caution children and adolescents, pregnant women, and women of reproductive age about ENDS use, because of the potential for fetal and adolescent nicotine exposure to have long-term consequences for the brain development.
The main health risk from nicotine exposure is nicotine overdose by ingestion or through dermal contact, but the number of cases of such incidents due to the handling of the concentrated solution is not clear, since most countries do not monitor these incidents.
The inhalation of the aerosols delivered by ENDS can have some effects on health. Eyes and lungs can get irritated by exposure to propylene glycol, for instance.
Given the relatively short time since those products have entered the market and the lag time of many diseases such as cancer, there is, as of now, no conclusive evidence about the health risks of ENDS, and this evidence won’t likely be available for years or even decades. However, it is very likely that average ENDS use, produces lower exposures to toxicants than combustible products.
Bystanders can be exposed to second-hand aerosol that increases the background level of some toxicants, of nicotine, and of fine and ultrafine particles in the air. Therefore, exhaled aerosol is likely to increase above background levels the risk of disease to bystanders, especially in the case of some ENDS that produce toxicant levels in the range of that produced by some cigarettes. However, the levels emitted by ends are generally much lower than by conventional cigarettes. It is however unknown if this exposure will lead to an increased risk of disease among bystanders.
Although anecdotal reports indicate that some ENDS users have quit smoking using these products, their efficacy has not been systematically evaluated yet. Only a few studies have examined whether the use of ENDS is an effective method for quitting tobacco smoking.
In one trial that compared the use of ENDS, with or without nicotine, to use of nicotine patches without medical assistance in the general population, showed similar, although low, efficacy for quitting smoking. A recent study also shows some, although limited, effectiveness in real-world conditions.
It is likely that the use of ENDS will help some smokers to quit cigarettes, but more likely it may simply help to reduce the number of cigarettes but not quit entirely. Since it appears that the number of years of smoking is a more important factor than the intensity of smoking in generating health problems, dual use will have much smaller beneficial effects on overall survival compared with quitting smoking completely.
In considering ENDS as a potential cessation aid, smokers should first be encouraged to quit smoking and nicotine addiction using a combination of already approved treatments.
A report of the US Department of Health and Human Services consider that ENDS would provide public health benefits only in an environment where the appeal, accessibility, promotion, and use of cigarettes and other combusted tobacco products are being rapidly reduced.
Although ENDS present a range of potential benefits to smokers, there is an extensive and often heated debate about whether ENDS will prove to have a positive or negative impact on population health and particularly tobacco control. Areas of legitimate concern include avoiding nicotine initiation among non-smokers and particularly youth while maximizing potential benefits for smokers.
The limited existing survey data from a handful of countries show that experimentation with ENDS is increasing rapidly among adolescents, and that is itself of great concern even if most of the young ENDS users also smoke. There are also very limited data from very few countries about the evolution of the smoking epidemic in the presence of the ENDS boom.
Two potential circumstances can lead to what is named a gateway effect:
(i) the possibility that children (and generally non-smokers) will initiate nicotine use with ENDS at a rate greater than expected if ENDS did not exist; and
(ii) the possibility that once addicted to nicotine through ENDS, children will switch to cigarette smoking.
There is a possibility that everything that makes ENDS attractive to smokers (the so-called renormalization effect), may enhance the attractiveness of smoking itself and perpetuate the smoking epidemic.
There are other specific issues that are raised by electronic nicotine delivery systems :
Smokers will obtain the maximum health benefit if they completely quit both tobacco and nicotine use. In the context of the framework convention on tobacco control, the WHO recommends that electronic nicotine delivery systems should be regulated, and this is a necessary precondition for establishing a, so far not available, robust scientific basis on which to judge the effects of their use. These recommendations cover the sale of ENDS, their use in public spaces, the advertising and marketing of ENDS, the health claims made by ENDS manufacturers, and the clear labeling of nicotine products. The products themselves should be regulated in order to minimize the exposure of users and of bystanders to toxicants. More specifically, the promotion of ENDS should be impeded, as is their uptake by non-smokers, pregnant women and youth. Unproven health claims should be prohibited from being made about ENDS and existing tobacco-control efforts should be protected from commercial and other vested interests of the tobacco industry.
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