The Case Against Flavors in E-Cigarettes Is Stronger Than Ever

In my earlier AJPH commentary, I expressed concern about the failure of the US Food and Drug Administration to ban flavors in e-cigarettes.¹ Subsequent research has strengthened my concerns about the health effects of flavorings. There are many thousands of flavors in use, and it is necessary to test them in pure form as well as their combustion products—which can include a number of known toxins, in particular aldehydes—and interactions between them.²

Turning to the use of flavors to attract new users, especially adolescents, a growing body of work has examined what is termed “abuse liability,” which is measured by asking users just after using a product about their level of satisfaction with it and whether they would like more. A recent systematic review has brought this evidence together.³ In an analysis of 31 epidemiological studies that examined responses to flavors in e-cigarettes, Gades et al. concluded, “Non-tobacco flavors are highly valued and increase the abuse potential and appeal of e-cigarettes.”^3(p6) This finding received some support from the five animal studies reviewed—which Gades et al. concluded “suggest that sweetness and cooling flavors elicit reward-related behaviors and neuroplasticity on their own, as well as increase the rewarding properties of nicotine”^3(p6)—and from the 16 experimental studies—from which the authors concluded, “Sweet and cooling flavors had higher appeal and abuse potential compared to tobacco-flavor.”^3(p6)

Some researchers, including Gades et al., may see these results as encouraging if flavorings reduce smoking initiation or increase quitting. Here, too, there is now considerable evidence of problems, most recently summarized in an Australian National University report that can be considered the state of the art on e-cigarettes.⁴ For this report, Banks et al. drew on three previous systematic reviews, which they topped up with a further 12 studies. From the subsequent meta-analysis, Banks et al. concluded that those exposed to e-cigarettes were about three times as likely to take up smoking combustible cigarettes.

Banks et al. also examined e-cigarette use and relapse in those who had quit combustible cigarettes, and, although only three studies were included, they too showed an increased risk among e-cigarette users. Finally, noting that most evidence cited in support of e-cigarettes as quitting aids is from studies that are part of a clinical package that includes supervision and support, Banks et al. concluded, “There is insufficient evidence that nicotine e-cigarettes are efficacious outside the clinical setting.”^4(p272) Importantly, other research has concluded that, when used as a consumer product, e-cigarettes reduce the probability of quitting.⁵ In summary, promotion of e-cigarettes as consumer products that can reduce smoking is not supported by evidence, so any measure, such as a ban on flavors, that reduces their abuse liability is desirable from a public health perspective.

Inevitably, despite this evidence, e-cigarette advocates will argue that banning flavors will have undesirable consequences, such as increasing smoking. Fortunately, we have the experience of San Francisco, California, which implemented a ban on flavors in all tobacco products in January 2019, although penalties were delayed until April. Gammon et al. compared sales of tobacco products, including e-cigarettes, in San Francisco and two other California cities—San Jose and San Diego—that did not implement a ban.⁶ As intended, sales of flavored products fell dramatically, by 96%, in San Francisco, whereas there was no change in San Jose and a 10% fall in San Diego. However, crucially, there was no evidence of substitution of flavored products. Total tobacco sales fell by 25% in San Francisco, more than in the other two cities. This included a 23% decrease in sales of combustible cigarettes.

In summary, two years on, my concerns seem to have been confirmed.