Dai H - In the present study, the author sought to analyze the trends in self-reported secondhand aerosol (SHA) exposure among US adolescents and explored the connections between SHA, susceptibility to tobacco use, and exposure to e-cigarette marketing among never tobacco users. In US high school students, the prevalence of current electronic cigarette use increased dramatically from 11.7% in 2017 to 20.8% in 2018. It was noted that exposure to SHA from e-cigarettes is not harmless, as e-cigarette aerosol contains nicotine and potentially harmful substances, including carbonyl compounds, tobacco-specific nitrosamines, heavy metals, and glycols. In recent years, the utilization of e-cigarette may serve as a gateway to cigarette initiation, and e-cigarette makers have significantly increased their advertising expenditures. Findings suggested that exposure to SHA may increase the curiosity about e-cigarettes and the perceived pervasiveness of e-cigarette marketing, and may further increase the vulnerability to tobacco use among non-tobacco consumers.