The prevalence and popularity of electronic cigarettes or “vaping” have grown dramatically over the last several years in the United States. Although new studies targeting these products are being done at increasing frequency, there remains a relative paucity of data regarding the long-term risks. Proponents argue that they can be used as a cessation tool for smokers, or failing that, a safer replacement for traditional cigarettes. Opponents make the case that the perception of safety could contribute to increased use in people who may have otherwise never smoked, leading to an overall increase in nicotine use and addiction. This is most readily seen in the adolescent population, where use has skyrocketed, leading to concerns about how electronic cigarettes are marketed to youth, as well as the ease of access.
Basics of vaping (devices)
In its most basic form, an electronic cigarette consists of a battery that powers a heating coil. This heating coil applies heat to a wick, which is soaked in liquid, “vape juice,” converting it into a vapor that is then directly inhaled. However, there can be many variations on this simple theme. Early generation products resembled traditional cigarettes in size and shape and were marketed as smoking cessation aids. Newer devices have abandoned this look and strategy. Preloaded cartridges have been replaced by large tanks that the user can fill with the liquid of their choosing. Multiple tanks can be purchased for a single device, enabling the user to have multiple flavors or various levels of nicotine dosing on hand for quick changing, depending on user preference or mood. Additionally, there are variable voltage settings, resulting in different styles of vapor and/or “throat hit” (the description of the desired burning vs smooth effect of the vapor on the oropharynx). This type of device invites experimentation. Multiple flavors can be used in isolation or mixed together at various temperatures. It no longer resembles classic cigarettes, and the flavor and experience are more prominently promoted. One can see that this device has more appeal to a “never smoker” than the original products, and there is concern that it is being marketed as such with some success (Dinakar C, et al. N Engl J Med. 2016;375[14]:1372).
E-liquid
Perhaps more important than the devices themselves is an understanding of the components of the liquid used to generate the inhaled aerosol.
Typically, four components are present:
• Propylene glycol
• Vegetable glycerin
• Flavoring
• Nicotine
The first two components are generally considered nontoxic, based on their use as food additives. However, inhalation is a novel route of entry and the long-term effects on the respiratory tract are unclear.
The third component, “flavorings,” is a catch-all term for the hundreds of different flavors and styles of e-liquids available today, ranging from menthol to fruit or candy and everything in between. It is difficult to account for all the potential effects of the numerous flavorings being used, especially when some are combined by the end user to various degrees.
Nicotine is present, specified in varying doses. However, vaping style, experience, and type of device used can dramatically affect how much is absorbed, making dosages difficult to predict. Additionally, labeled doses are prone to wide ranges of error (Schraufnagel DE, et al. Am J Respir Crit Care Med. 2014;190[6]:611).