Everyone should be aware of the unequivocal facts that smoking tobacco cigarettes is a leading cause of several serious medical diseases; that nicotine is a powerfully addictive substance; and despite the availability of several therapies that are approved by the US Food and Drug Administration (FDA), the vast majority of smokers who try to quit have incredible difficulty maintaining abstinence. Although alternate forms of nicotine delivery, such as nicotine patches and nicotine nasal spray, have been around for many years, electronic cigarettes (e-cigarettes) have achieved impressive popularity in a very short period.
Many individuals — young and old, smokers and nonsmokers — are using e-cigarettes with little knowledge of the potential harmful health effects. Available data from the past few years show dramatic increases in awareness and use of e-cigarettes, especially among adolescents. The majority believe that e-cigarettes not only are safer than conventional cigarettes, but also are effective tools to aid in smoking cessation.
Many clinicians stand ready to advocate for any means to reduce cigarette smoking, yet too is little known about e-cigarettes to endorse these products as a cessation tool at this time. E-cigarette ingredients are not standard across the industry, and the levels of those substances remain variable from product to product. Recent research shows quite clearly that the fluid and aerosol in e-cigarettes contains known toxins, including propylene glycol, heavy metals, volatile organic compounds, and tobacco-specific nitrosamines. 
The good news is that these toxic agents are found in far lower concentrations than in regular cigarettes. However, the long-term effects of exposure to some of these compounds are unknown and require additional research. Other studies have shown that e-cigarette “vaping” adversely affects lung physiology similar to that observed with conventional cigarettes.
The medical community must acknowledge the fact that nicotine itself (referred to as “juice” in e-cigarette cartridges) is a powerfully addictive substance and is a toxin when ingested in large quantities. Nicotine poisoning is most likely to occur in small children who tamper with e-cigarette cartridges; this is a potential, yet unknown, risk that is nearly impossible with cigarettes and nicotine replacement products. Moreover, repeated exposure to nicotine will predictably increase physiologic variables (heart rate) and stress system reactivity (cortisol). On this basis, it seems clear that e-cigarettes containing nicotine should not be promoted as harmless alternatives to regular cigarettes.
Other concerns about e-cigarettes should also be considered. First, the use of these products could prolong actual smoking cessation using FDA-approved therapies. Specifically, people wanting to stop smoking may try e-cigarettes first in lieu of using one of several effective over-the-counter forms of nicotine replacement (ie, patch, gum, or lozenge) or talking to their doctor about using an FDA-approved medication for smoking cessation (ie, bupropion or varenicline).
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Second, data are emerging to show that some users are not stopping cigarette use, but concurrently using e-cigarettes (“dual use”) in all the places where they would have otherwise have been unable to smoke (eg, restaurants, airports, and the workplace). This presents an interesting public health question because many smokers, as a consequence of smoking bans in public places, have become more motivated to quit smoking.
Finally, and perhaps most problematic, is the very real possibility that e-cigarettes may serve as an initiation device for young people, who may eventually transition to regular cigarettes when they reach the legal age to purchase those products.