While e-cigarettes are not without health risks, they are likely to be far less harmful than conventional cigarettes, according to a congressionally mandated report from the National Academies of Sciences, Engineering, and Medicine.
The committee that conducted the study concluded that e-cigarettes contain fewer numbers and lower levels of toxic substances than conventional cigarettes. In addition, using e-cigarettes may help adults who smoke conventional cigarettes quit smoking. However, the long-term health effects are not yet clear. Among youth—who use e-cigarettes at higher rates than adults—there is substantial evidence that e-cigarette use increases the risk of transitioning to smoking conventional cigarettes.
E-cigarettes are a diverse group of products containing a heating element that produces an aerosol from a liquid that users can inhale via a mouthpiece, and include a range of devices such as "cig-a-likes," vape tank systems, and vape mods. Use varies substantially across demographic groups. The committee examined more than 800 peer-reviewed scientific studies about their effects.
"E-cigarettes cannot be simply categorized as either beneficial or harmful," said David Eaton, chair of the committee that wrote the report, and dean and vice provost of the Graduate School of the University of Washington, Seattle. "In some circumstances, such as their use by nonsmoking adolescents and young adults, their adverse effects clearly warrant concern. In other cases, such as when adult smokers use them to quit smoking, they offer an opportunity to reduce smoking-related illness."
The reports conclusions include the following:
- There is conclusive evidence that exposure to nicotine from e-cigarettes is highly variable and depends on the characteristics of the device and the e-liquid, as well as on how the device is operated. But there is substantial evidence that nicotine intake from e-cigarettes among experienced adult e-cigarette users can be comparable to that from conventional cigarettes.
- There is conclusive evidence that most e-cigarettes contain and emit numerous potentially toxic substances. But there is substantial evidence that except for nicotine, exposure to potentially toxic substances from e-cigarettes (in typical use) is significantly lower compared with conventional cigarettes.
- There is substantial evidence that e-cigarette use results in symptoms of dependence on e-cigarettes. But there is moderate evidence that risk and severity of dependence is lower for e-cigarettes than conventional cigarettes.
- There is moderate evidence that variability in the characteristics of e-cigarette products is an important determinant of the risk and severity of dependence on e-cigarettes.
- There is conclusive evidence that completely substituting e-cigarettes for conventional cigarettes reduces users' exposure to many toxicants and carcinogens present in conventional cigarettes.
- There is substantial evidence that completely switching from regular use of conventional cigarettes to e-cigarettes results in reduced short-term adverse health outcomes in several organ systems.
- There is substantial evidence that e-cigarette use by youth and young adults increases their risk of ever using conventional cigarettes.
- There is conclusive evidence that e-cigarette use increases airborne concentrations of particulate matter and nicotine in indoor environments compared with background levels. But there is moderate evidence that second-hand exposure is lower from e-cigarettes than conventional cigarettes.
- There is no available evidence whether or not e-cigarette use is associated with intermediate cancer endpoints in humans. (An intermediate cancer endpoint is a precursor to the possible development of cancer; for example, polyps are lesions that are intermediate cancer endpoints for colon cancer.) But there is limited evidence from animal studies using intermediate biomarkers of cancer to support the hypothesis that long-term e-cigarette use could increase the risk of cancer.
- There is conclusive evidence that e-cigarettes can explode and cause burns and projectile injuries. Such risk is significantly increased when batteries are of poor quality, stored improperly, or are being modified by users.
Source: National Academies of Sciences, Engineering, and Medicine, January 23, 2018.