Electronic Cigarettes: Scientific Evidence versus Social Cost
Omar Martinez, Pharm. D. Intern & Jennifer Seltzer, PharmD
April 25th, 2012
Cigarette smoking prevalence in the U.S. is approximately 20% and has higher rates among men, American Indians, and lower socioeconomic populations.1 Roughly 80% of U.S. smokers began smoking before age 18, with several factors contributing to tobacco use, such as peer pressure and lack of parental involvement.2 When inhaled, tobacco smoke, which contains nicotine and over 4000 additional compounds, deposits toxic and carcinogenic chemicals into the lower airways. Health risks of smoking include hypertension, cardiac ischemia, chronic airway obstruction, reduced wound healing, and various cancers.3The development of electronic cigarettes (e-cigs) in the mid-2000s has spurred people to seek data concerning this new smoking alternative, as Google searches for "electronic cigarettes" have risen by as much as 5000% over the last several years.4 Although efficacy data in smoking cessation are lacking, e-cigs have been used either as a safer alternative to traditional cigarettes or as a means to quit smoking.4, 5
Similarities and differences between e-cigs, also called electronic nicotine delivery systems (ENDS), and traditional cigarettes depend on appearance and physiochemical properties. MarlboroTM cigarettes contain several ingredients including tobacco (≥0.1% w/w), water, sugar, propylene glycol, glycerol, ammonium hydroxide, and flavoring.6 In comparison, e-cigs, including brands like NJOY and Liberty™ Stix, are structured as a cartridge of propylene glycol and nicotine, an atomizer for liquid vaporization, and a battery to heat the atomizer.7 Chemical analyses of e-cig cartridges show variable nicotine concentrations in contrast to the manufacturer's package label.8 Variation can be found in the airflow, life of cartridges, and the quality of aerosols between e-cig brands, which can be attributed to different mechanical specifications.9 Vaping, the act of using an e-cig, does not produce combustion like traditional cigarettes and causes the user to inhale vapor, not smoke; e-cig users are called vapers.10 One study demonstrated that vaping produced uneven doses and required more suction over time for the vaper to puff.7 Moreover, e-cigs produce vapors containing small amounts of carcinogenic tobacco-specific nitrosamines at substantially lower concentrations than traditional cigarettes. Diethylene glycol, a toxic component of antifreeze, has also been found in one e-cig product, but may have been a contaminant.4, 10-12 E-cig users do not inhale carbon monoxide while vaping and, consequently, do not produce increased exhaled carbon monoxide levels compared to traditional cigarette smoking.12
E-cig benefit for management of tobacco dependence is controversial due to a paucity of long-term safety results and randomized, controlled data. Less stringent studies and case reports have been published, though, which address e-cig impact on traditional cigarette use/discontinuation. In an Italian prospective study, investigators assessed e-cig use in 40 chronic refractory smokers who were not seeking to quit. Results showed an 80% reduction in traditional cigarette use and minimal e-cig adverse effects, with lower mean carbon monoxide exhalation among e-cig users, correlating with decreased tobacco usage.13 Surveys from 104 chronic vapers in Pennsylvania showed general daily e-cig use, preference for higher battery power to increase vapor production, and dramatic drops in tobacco use. A majority of participants believed e-cigs were helpful to quit smoking.5 Etter and cohorts14 administered online questionnaires and found that most vapers were men who used e-cigs to deal with smoking habits and believed them to be less harmful than traditional cigarettes. In a case series, 3 refractory Caucasian smokers with significant pack-year histories found e-cigs helpful for giving up smoking and remaining tobacco free.15 A researcher hypothesized that the act of using a cigarette-like object to simulate cigarette smoking serves as a "placebo effect" and may contribute to increased rates of smoking cessation.9
Due to the 2010 case verdict in Sottera, Inc. v. Food and Drug Administration (FDA), e-cigs have been classified as tobacco products because nicotine is not marketed therapeutically.16 The FDA is developing regulations for these products including registration procedures, product listings, and good manufacturing practices.17 Concerns about the encouragement of smoking habits among adults and minors has led to proposals and enactments of prohibitive legislation in several states and jurisdictions.18, 19 The U.S. Air Force recently endorsed a ban of e-cigs, citing similarity to tobacco products and limited data as smoking cessation aids.20 E-cigs also have the potential for mechanical problems, as a Florida man experienced when one exploded during use.21
In 2009, the Family Smoking and Prevention Tobacco Act, signed by President Obama, allowed the FDA to regulate tobacco products, which now include e-cigs.11 In addition, the World Health Organization and the FDA have requested e-cig companies to withhold claims of benefit in smoking cessation, as e-cigs have been shown to contain polyaromatic hydrocarbons, acetaldehyde, and benzene.10, 14 Future e-cig research should involve studies assessing vapor composition, mutagenicity, long-term use, addictive potential, and reduction of smoking behavior compared to nicotine replacement therapies (NRT). Using e-cigs for lung deposition of pharmaceuticals is another option for research.4 Because substantial efficacy and safety data on e-cigs are lacking, NRT or non-nicotine products in combination with behavioral therapy provide the most evidence for success in those smokers desiring to quit smoking.22 However, with the serious health consequences of chronic nicotine exposure, e-cigs require further consideration to determine whether they may have a safe, effective clinical role in smoking cessation efforts.