Vaping and e-cigarette use. Mysterious lung manifestations and an epidemic
Introduction
Electronic (e)-cigarettes are drug delivery devices primarily used for the inhalation of nicotine and marijuana, in the form of tetracannabinoids (THC). The modern e-cigarette was invented in 2003, entered the global market in 2007, and has rapidly become popular across the world. There are many types of e-cigarettes, from cig-a-likes to vape pens and box Mods to pod-devices, but they all involve heating and aerosolization of e-liquids (Figure 1). The base ingredients of e-liquids, nicotine, propylene glycol and glycerin, have an unappealing flavor on their own such that chemical flavorants are added to >99% of e-liquids to increase the appeal to users.
Use patterns of electronic (e)-cigarettes and vaping devices differ greatly across age groups. Adults most commonly pick up vaping in the setting of conventional cigarette smoking, either adding it into their smoking practice (dual use; 55% of adult e-cigarette users) or switching to e-cigarettes as a means to stop smoking [1]. While 3.2% of all adults use e-cigarettes, the rates are much higher in young adults 18–24 years-old, of whom 7.6% vape, and higher still in high school students, of whom 27.5% have used a vaping device within the past month [2,3] (Figure 2). Sadly, middle school students as young as age 11 also have high rates of e-cigarettes use (10.5%) [4] (Figure 2). While adult e-cigarette users are most often active smokers or ex-smokers, 44.3% of adolescents and young adults were never smokers before e-cigarette use [5] (Figure 3). Of concern, it has been shown that e-cigarette use in never smokers leads to higher initiation of cigarette smoking, up to fourfold [6, 7, 8]. A great deal of research to date has been focused on comparing e-cigarette use to cigarette smoking to assess the potential benefit of switching from smoking to vaping as a form of harm reduction, while less focus has been on the health effects of vaping in non-smokers, for whom the rates of vaping continue to rise, particularly in the youth [9••,10] (Figure 2).
E-cigarettes have been marketed as a form of harm reduction from traditional cigarette smoking, but neither the safety nor the efficacy of these devices has been established, and little is known about the short and long term pulmonary and systemic health effects. This review focuses on the known and unknown toxins contained in e-cigarette aerosols, lung diseases induced by vaping, and the predicted long-term consequences of e-cigarette use (Figure 4). Particular attention is given to the e-cigarette or vaping product use-associated lung injury (EVALI) epidemic that began in 2019 and is ongoing (Figure 2, Figure 3, Figure 4).
Section snippets
Inhalant toxicology of e-cigarettes and vaping products
E-cigarettes are devices composed of a power source, heating element, and liquid reservoir that heat and aerosolize e-liquids to make vapor that is inhaled into the lungs in a process known as vaping. E-liquids are most often composed of (1) addictive substances such as nicotine and/or tetrahydrocannabinol (THC), (2) flavorings, and (3) solvents (e.g. propylene glycol or vegetable glycerin). There are many types of vaping devices, but the most frequently used include pod vapes, box mods, and
Currently known pulmonary manifestations of vaping
E-cigarettes have been marketed as a form of harm reduction from traditional cigarette smoking, but neither the safety nor the efficacy of these devices has been established, and little is known about the short and long term pulmonary and systemic health effects. There have been increasing reports in the literature of negative pulmonary effects with the recent epidemic of e-cigarette or vaping product use-associated lung injury (EVALI) (discussed in detail below) being the most immediately
EVALI
The national outbreak of e-cigarette, or vaping, product use-associated lung injury (EVALI) has been the first vaping related disease to affect thousands of people (2807 hospitalized cases as of February 2020). At its core, it is a chemical inhalation injury, most likely caused by heating, aerosolization and inhalation of Vitamin E within THC liquids and vape pens. Examination of airways and lungs of those affected has yielded a pattern of epithelial and alveolar damage [55]. Neutrophils and
Predicted long-term health consequences
Conventional tobacco has been smoked for over 5000 years and is very well known to cause a myriad of long-term health problems, not the least of which is lung disease [67]. Because modern vaping devices have been on the market for less than 16 years, and only widely used for 5, very little is known about how chronic use will affect human health. Murine data suggest that some vapers will develop emphysema, heart disease, renal failure, and even liver fibrosis, but these diseases will be couched
Conclusions
Vaping involves the introduction of hundreds to thousands of chemicals into the delicate airways and alveoli of the lung, causing a myriad of both acute and chronic diseases in humans. Some diseases such as EVALI, HSP and acute eosinophilic pneumonia are already recognized, but as more and more people begin vaping and vape for longer periods of time, more diseases both in the lung and throughout the body will become apparent. Prevention of these known and unknown effects of vaping is a priority
Funding
Dr. Crotty Alexander’s salary was supported in part by the VA San Diego Healthcare System and grants from the National Institutes of Health (NIH R01HL147326 to LCA) and the Tobacco-Related Disease Research Program (TRDRP T30IP0965 to LCA and 26IP-0040 to LCA).
Conflict of interest statement
Nothing declared.
References and recommended reading
Papers of particular interest, published within the period of review, have been highlighted as:
•• of outstanding interest
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