Michael Kotlyar, PharmD, MS
University of Minnesota, Minneapolis
This session is available at https://aapp.org/ed/course/e-cigarettes-update-safety-and-effectiveness
E-cigarette use has been increasing rapidly in the United States resulting in a considerable debate regarding the harms or potential benefits associated with the availability of these products. In this presentation, Dr. Maciej Goniewicz reviewed the differences between combustible cigarettes and e-cigarettes, discussed the relative toxicity of these products, and discussed data regarding the use of e-cigarettes as a method by which smokers of combustible cigarettes can quit.
Although e-cigarettes differ in shape, size, and other characteristics, they have several common features. These include a power source (i.e., battery), a heating element, and an electronic sensor (or something similar) that detects airflow through the device. The liquid used in e-cigarettes (often referred to as e-liquid) generally contains nicotine, propylene glycol, vegetable glycerin, water, and flavorings. The flavorings play an important role in the appeal and sensory aspects of e-cigarettes with fruit, sweet, beverage, and traditional tobacco flavors available. It should be noted that e-cigarettes are increasingly used to deliver other drugs such as THC / CBD, although a discussion of these was outside the scope of this presentation.
Much of the presentation focused on the topic of absolute risk vs. relative risk. Tobacco is the number one preventable cause of disease, disability, and death in the United States with approximately 480,000 premature deaths annually in the United States attributable to smoking-related illnesses. Combustible tobacco, which contains more than 7,000 chemicals including hundreds of toxic compounds, is particularly dangerous. When evaluating the health impacts of e-cigarettes, there are many factors to consider which include the relative harm of e-cigarettes compared to combustible tobacco, the rates of vaping and smoking initiation that occur as a result of e-cigarettes (particularly among young people) and what effect e-cigarettes may have on smoking cessation rates.
Sources of toxicants in e-cigarettes are either from the product itself or can be generated during use (e.g., byproducts of thermal degradation, degradation byproducts generated during storage). It’s important to note that most of the safety assessments of chemicals in e-liquids come from the food industry and relate to the toxicity of these compounds when ingested. There is, however, little data about the safety of these chemicals when inhaled. The National Academies of Science, Engineering, and Medicine in its 2018 report on the public health consequences of e-cigarettes concluded that e-cigarettes emit numerous potentially toxic substances but fewer than the number found in tobacco smoke. Exclusive e-cigarette users have significantly higher toxicant concentrations compared to never users (i.e., increased absolute risk) but lower than in cigarette smokers (i.e., lower relative risk). When smokers substitute e-cigarette for cigarettes, concentrations of toxicants decrease however concentrations of toxicants are similar between cigarette smokers and those who use both cigarettes and e-cigarettes (otherwise known as dual users). So an important message for those who are considering using e-cigarettes is that they must completely stop smoking cigarettes.
Another consideration in evaluating the overall health effects of e-cigarettes is if on a population level e-cigarettes are replacing or promoting smoking. A recent randomized controlled study in which smokers were randomized to either nicotine replacement therapy (NRT) or e-cigarettes found that 1-year abstinence rates were higher among the e-cigarette group however many of those randomized to e-cigarettes continued to use these products a year later raising questions about risks of long-term use. It is also important to consider how e-cigarettes impact tobacco use initiation considering that among teenagers, rates of e-cigarette use now exceed that of all other tobacco products. The use of pod systems (a newer type of e-cigarette) by adolescents may result in higher nicotine concentration that observed in those who regularly smoke combustible cigarettes and have been shown to lead to nicotine dependence. There is an additional concern that the use of e-cigarettes among youth can be a gateway to subsequent smoking. Dr. Goniewicz concluded that the use of e-cigarettes will result in a net public health benefit.
Take home points