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E-cigarettes: Extensive research required!

Comment by Eugenio Greco, EACPR Prevention, Epidemiology and Population Science Section

Electronic cigarettes: A Policy Statement from the American Heart Association
A. Bhatnagar et al.
Circulation 2014; DOI: 10.1161/CIR.0000000000000107


The American Heart Association (AHA) in partnership with major public health organisations, has made major strides in tobacco use prevention and cessation, and the tobacco control efforts have cut in half the youth smoking rate from 1997 to 2007 and have saved >8 million lives in the past 50 years. Its statement reviews the latest science concerning the new class of tobacco products: electronic cigarettes (e-cigarettes).

It provides an overview on design, operations, constituents, toxicology, safety, user profiles, public health, youth access, impact as a cessation aid, and second-hand exposure.
In particular, it is clear that:

  • It is not known whether the emerging e-cigarette technology will shift people from combustible products to the exclusive use of e-cigarettes or whether dual use will persist.
  • Some studies have examined the health effects of e-cigarettes by considering the constituents of their aerosol and their known toxicities and through toxicological evaluation of e-cigarette liquids and aerosols. The constituent and toxicant levels within the e-liquid and aerosol vary depending on the e-liquid formulation and the specific design of the device. Exposure to levels and types of metals or other materials within the aerosol depends on the material and other engineering features of the heating coils; some of these materials can be aerosolized and inhaled; their levels are generally low, and little is known about the toxicity of prolonged inhalation of low levels of this metals.
  • Importantly trace levels of tobacco-specific N-nitrosamines, polycyclic aromatic hydrocarbons, and volatile organic compounds in the e-liquid and vapour have been reported, however, the amounts are deemed too low to cause human risk.
  • Nicotine is delivered by most but not all e-cigarette products; most e-liquids contain 36 mg/mL, 24 mg/mL, 18 mg/mL, 12 mg/mL, or 6 mg/mL nicotine and are qualified by the manufacturers as high, medium, or low nicotine strength. 1 regular cigarette contains ≈10 to 15 mg of nicotine and delivers a systemic dose of ≈1 mg of nicotine. Testing has revealed that the nicotine content noted in some e-cigarette products and refill solutions has been incorrect and either overestimates or underestimates the amount of nicotine but still delivered nicotine much more slowly than tobacco cigarettes.
  • Most of the adverse health effects of smoking are caused by tobacco combustion products, but there are some health concerns that are related to nicotine per se, as release of catecholamines (with hemodynamic effects: increase in heart rate, a transient increase in blood pressure, vasoconstriction of coronary and other vascular beds), adverse effects on lipids, and induction of insulin resistance. Nicotine has also been reported to produce endothelial dysfunction and to cause fetal teratogenicity.
  • Analyses of emissions from e-cigarettes have found primarily formaldehyde, acetaldehyde, and acrolein, along with low levels of toluene, xylene, benzene, butadiene, and propylene oxide. The risk of exposure to low levels of these compounds is unknown.

The conclusion of the statement is that the AHA considers the e-cigarettes that contain nicotine to be tobacco products, but e-cigarettes, compared with cigarettes and smokeless tobacco, do not contain or have lower levels of several tobacco-derived harmful and potentially harmful constituents.

Moreover, because e-cigarettes are relatively new products, their health effects have not been well studied; little is known about their use and their characteristics; their long-term health effects on individual users and the potential harm incurred by long-term use remains completely unknown; therefore extensive research is required to address these questions.