The E-Cigarette Debate: What Counts as Evidence?

Amy Lauren Fairchild, PhD, MPH; Ronald Bayer, PhD; Ju Sung Lee, MHA


Am J Public Health. 2019;109(7):1000-1006. 

In This Article


The point at which the PHE and NASEM reports came closest to agreement centered on the risks of e-cigarettes compared with combustible products. Both reports stressed that e-cigarettes are "safer" but "not safe." But quantifying the relative risks had been a point of contention for years: are e-cigarettes marginally safer, thus still too risky to substitute for combustible products, or are they substantially safer?

To be considered "conclusive," the NASEM committee required evidence from "many supportive findings from good quality-controlled studies (including randomized and non-randomized controlled trials) with no credible opposing findings."[11] (p5) It is therefore noteworthy that NASEM concluded, "There is conclusive evidence that completely substituting e-cigarettes for combustible tobacco cigarettes reduces users' exposure to numerous toxicants and carcinogens present in combustible tobacco cigarettes."[11] (p11)

Unresolved was how aggressively e-cigarettes should be promoted to smokers as safer. Here a sharp divide informed a reading of what the evidence demanded. In a public comment, the NASEM chair stated, "While one might conclude from our report that a smoker who switches to e-cigarettes has reduced his or her risk, there is some uncertainty and the evidence suggests that they must switch completely."[16] In other words, he and other committee members who discussed the report in public appeared troubled by lingering uncertainty. Despite the report findings, they were reluctant to endorse policy initiatives that might favor the broad-scale substitution of e-cigarettes for combustible products. They indicated little concern about the extent to which public opinion had come to see e-cigarettes as equally or more risky than combustibles.[17]

PHE's position differed starkly: it not only endorsed but also promoted e-cigarettes. While acknowledging that there were some risks and uncertainties and that e-cigarettes could not be called "safe," PHE has continued to maintain that vaping is "at least 95% less harmful than smoking"[8] (p20) (Figure B, available as a supplement to the online version of this article at This risk assessment, which to some was an unwarranted overstatement based on limited evidence and conflicts of interest,[18] was, to the report's authors, essential: they aimed to "communicate the large difference in relative risk unambiguously so that more smokers are encouraged to make the switch from smoking to vaping."[8](p20) A central concern of PHE was the extent to which surveys indicated that misperceptions about the relative safety of e-cigarettes discouraged tobacco smokers from switching. Underscoring the importance of the widespread availability of e-cigarettes, the press release for the PHE report stated, "To become truly smoke free, Trusts should ensure e-cigarettes, alongside nicotine replacement therapies are available for sale in hospital shops."[14] Martin Dockrell, Head of PHE Tobacco Control, envisioned policy that extended beyond the report recommendations: "We would certainly encourage [hospitals] to make at least some single occupancy rooms where people can vape."[19] He also called for the creation of shared lounges for vapers in hospitals.