Electronic cigarettes, also known as e-cigarettes, are battery-powered devices that contain nicotine liquid and allow users to inhale vapor instead of tobacco smoke. Since their emergence in the U.S. market around 2007, e-cigarette use among adults and youth has risen exponentially. As of 2018, almost 4% of adults and 20% of high school students reported current e-cigarette use according to national surveys. Conclusive research on the health impacts of e-cigarettes remains limited due to the relatively short time period they have been widely used. While e-cigarettes likely pose fewer risks compared to combustible cigarettes, both their long-term health effects and their potential impact on public health goals of reducing tobacco use still remain largely uncertain.
E-cigarettes work by heating a liquid solution called e-liquid that typically contains nicotine, propylene glycol or glycerol, and flavorings. When the user inhales, the e-liquid is heated into an aerosol that is inhaled as vapor rather than smoke. Most devices contain a heating element and lithium-ion batteries. Disposable e-cigarettes are pre-filled and non-refillable while rechargeable e-cigarettes allow the user to refill e-liquid. Early research on health effects has found that the aerosol contains lower levels of toxins compared to combustible cigarettes but does contain some harmful components like formaldehyde and heavy metals. While less toxic than cigarette smoke, long-term studies are still needed to fully evaluate health risks from e-cigarette aerosol inhaled deep into the lungs over many years.
At the population level, the impact of e-cigarettes also depends on whether they result in more or fewer smokers of combustible cigarettes. If primarily used as a substitute product by current smokers to reduce harm, e-cigarettes could positively impact public health over the long run. If they draw in new youth users and primarily act as a “gateway” product leading to smoking initiation, they could negatively impact public health. Current research on this issue has produced mixed results with some studies supporting both perspectives. According to the National Academies of Sciences, Engineering, and Medicine, e-cigarettes are likely less dangerous than cigarettes but their absolute magnitude of harm and whether they undermine cessation at the population level remains highly uncertain. More research is urgently needed to understand the long-term trajectories of risk for youth e-cigarette users.
Part of the challenge of studying e-cigarette health effects is that the devices and e-liquids have rapidly evolved over time. Early generation devices emitted higher levels of toxicants compared to later models due to less efficient heating mechanisms. New disposable devices now dominate many markets and differ substantially from early rechargeable tank models. E-liquid formulations have also diversified with increased niche labeling like “salts” versions of nicotine aimed at device-dependent users. Flavors have proliferated with over 15,600 unique e-liquid flavors documented, many of which are candy and fruit varieties appealing to youth. Chemical evaluation of the thousands of flavoring additives used remains sparse, though some research shows certain compounds may carry increased toxicity risks when inhaled. Overall, the lack of standards and rapid product innovation hinders the ability to draw definitive conclusions from existing research about health impacts of this quickly changing class of products.
At the regulatory level, e-cigarettes remain controversial with divergent views on appropriate oversight. In the United States, the FDA extended regulatory authority to e-cigarettes in 2016 but allowed prolonged compliance periods for products on the market. The FDA banned sales of e-cigarettes to minors nationally in 2018. Many states and localities have implemented more comprehensive restrictions especially aimed at limiting youth access and exposure. For example, some areas have prohibited vaping indoors where smoking remains banned. In contrast, some other countries like the United Kingdom have formally embraced a harm reduction model by endorsing medicalized e-cigarettes to support cessation. International regulatory approaches vary widely based on differing cultural and policy frameworks surrounding tobacco and nicotine.
Overall, while research has grown substantially in a short time since the introduction of modern e-cigarettes in the late 2000s, very large uncertainties remain about the impact of these rapidly changing products on both individual and public health. Long-term multi-generational studies are still needed but will take decades to fully observe. In the interim, regulators face difficult trade-offs balancing potentially reduced-risk opportunities for adult cigarette smokers against threats to prevent youth uptake and addiction. More research is warranted on not just toxicology and clinical endpoints but also how social and cultural factors drive adoption trends, especially among youth. With thousands of new initiators every month, policies around e-cigarettes will remain controversial and dynamic as evidence and products continue to evolve.
Electronic cigarettes represent a disruptive technology that complicates traditional frameworks of tobacco control. While initial research indicates they pose lower individual health risks than smoking, uncertainty persists around long-term impacts, gateway effects on youth, and population-level effects on smoking rates. Given dynamic product innovations and rapid diffusion especially among youth and young adults, ongoing monitoring and research is urgently needed to guide sound policy and regulation of these popular but still not fully understood products. More conclusive data from diverse disciplines are required to comprehensively evaluate both the risks and potential opportunities of electronic cigarettes.
Andrew Stroud