BACKGROUND AND AIMS: Exposure to chemicals contributes to harm from nicotine products, and e-cigarette communications often refer to chemicals. However, while e-cigarette studies commonly measure perceived harmfulness of e-cigarettes relative to cigarettes, few have assessed comparative perceptions about chemicals. This study measured perceived levels of harmful chemicals in e-cigarettes compared with cigarettes, and associations with e-cigarette/cigarette relative harm perceptions, e-cigarette use, and interest.

DESIGN AND SETTING: Online cross-sectional survey of adults/young adults from a nationally representative research panel in the United States conducted in January 2021. Participants were independent samples of 1018 adults who smoked cigarettes and 1051 young adult non-smokers (ages 18-29).

MEASUREMENTS: Participants were asked their perceptions of the level of harmful chemicals in e-cigarettes versus cigarettes (fewer/about the same/more/don't know), perceived harmfulness of using e-cigarette versus cigarettes (less/about the same/more/don't know), and their current e-cigarette use and use interest.

FINDINGS: About 20% of all participants believed e-cigarettes contain fewer harmful chemicals than cigarettes, while 36% of adult smokers and 25% of young adult non-smokers responded "don't know". Participants more frequently reported "don't know" to the chemicals item than the harm item. About half (51-55.7%) of those who believed e-cigarettes contain fewer harmful chemicals also believed e-cigarettes are less harmful than cigarettes. Both beliefs were associated with higher odds of interest in using e-cigarettes (less harmful belief, odds ratio [OR]=5.53, 95% confidence interval [CI] 2.93-10.43; fewer chemicals belief, OR=2.45, 95% CI 1.40-4.29) and past 30-day e-cigarette use (less harmful belief, OR=2.53, 95% CI 1.17-5.44; fewer chemicals belief, OR=5.09, 95% CI 2.31-11.19) for adults who smoke, but not young adult non-smokers.

CONCLUSIONS: In the United States, most adults who smoke cigarettes and young adult non-smokers do not appear to think that e-cigarettes have fewer harmful chemicals than cigarettes, and many are uncertain about how these levels compare.