The Health Effects of Electronic Cigarettes

Posted by • October 6th, 2016

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Although the sale of e-cigarettes is prohibited in some countries, it is legal in most, including the United States, where the FDA recently finalized rules for the regulation of e-cigarettes as a tobacco product. The U.S. market for e-cigarettes is now estimated to be worth $1.5 billion, a number that is projected to grow by 24.2% per year through 2018. Global sales are predicted to reach $10 billion by 2017. The use of electronic cigarettes is growing, and some hope that they will replace what is felt to be the more dangerous nicotine-delivery system — cigarettes. However, data on the long-term safety of e-cigarettes are still being gathered and expanded upon in a new Review Article.

Clinical Pearl

What are the components of an electronic cigarette?

E-cigarettes, also known as electronic nicotine-delivery systems, are devices that produce an aerosol by heating a liquid that contains a solvent (vegetable glycerin, propylene glycol, or a mixture of these), one or more flavorings, and nicotine, although the nicotine may be omitted. The evaporation of the liquid at the heating element is followed by rapid cooling to form an aerosol. E-cigarette aerosol is directly inhaled (or “vaped”) by the user through a mouthpiece. Each device includes a battery, a reservoir that contains the liquid, and a vaporization chamber with heating element. The composition of the aerosol that is generated depends on the ingredients of the liquid, the electric characteristics of the heating element, the temperature reached, and the characteristics of the wick. The constituents of the aerosol generated by e-cigarettes and inhaled by the user are more directly relevant to health than the ingredients of e-cigarette liquids.

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Clinical Pearl

Who is using e-cigarettes?

In 2010, a total of 1.8% of U.S. adults reported having used an e-cigarette at some time, a rate that rose to 13.0% by 2013; reports of “current use” increased from 0.3% to 6.8% during this period. Although tobacco smokers were among those most likely to be current users of e-cigarettes, a third of current e-cigarette users had never smoked tobacco or were former tobacco smokers. Of particular concern regarding public health has been the increasing experimentation with and use of e-cigarettes among persons younger than 18 years of age.

Morning Report Questions

Q: Do e-cigarettes help tobacco smokers quit smoking?

A: The efficacy of e-cigarettes as a smoking-cessation intervention remains uncertain owing to the limited data available from randomized trials. Furthermore, it is difficult to extrapolate the results of studies that used first-generation e-cigarettes to second- and third-generation devices that are more satisfying to users because of changes in aerosol characteristics, nicotine delivery, and the variety of flavors. Recent meta-analyses that have combined data from randomized trials and observational cohort studies have not shed further light on the efficacy of e-cigarettes as a smoking-cessation aid.

Q: Are the flavorings that are added to e-cigarette liquid considered harmless?

A: In 2014, there were an estimated 466 brands and 7764 unique flavors of e-cigarette products; this heterogeneity complicates research on potential health effects. Although some studies suggest that smoking e-cigarettes may be less dangerous than smoking conventional cigarettes, more needs to be learned. A particular challenge in this regard is the striking diversity of the flavorings in e-cigarette liquids, since the effects on health of the aerosol constituents produced by these flavorings are unknown. Many of the liquid flavorings in e-cigarettes are aldehydes, which in some cases are present in concentrations sufficient to pose risks owing to the irritant characteristics of these compounds. Sweet-flavored e-cigarette liquids often contain diacetyl, acetyl propionyl, or both. These flavorings are approved for use in foods but have been associated with respiratory disease when inhaled during manufacturing processes. Some e-cigarette liquids are flavored with tobacco extracts, and these may contain tobacco-specific nitrosamines, nitrates, and phenol, although in far lower concentrations than those found in tobacco products.

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