Abstract
INTRODUCTION: Involuntary exposure to secondhand tobacco smoke (SHS) and secondhand aerosol from electronic cigarettes (SHA) persists in homes, vehicles, educational settings, and recreational spaces, increasing adolescents' risk of respiratory infections, asthma, and impaired lung development(1). The study aim was to examine among Spanish adolescents, aged 12-21 years, the associations between: 1) the presence of social models who smoke or vape (parents, siblings, peers, teachers); 2) self-perceived exposure to smoke or aerosol in physical environments (home, school, car, public spaces); 3) digital exposure to both anti-tobacco messaging and vaping-related content on social media and video platforms; and 4) age-based sales restrictions for nicotine products. We hypothesized that higher levels of physical or digital exposure and the presence of smoking or vaping role models would be associated with greater likelihood of trying conventional or electronic cigarettes. METHODS: We conducted a cross-sectional survey of 2823 students (mean age=13.8 ± 1.2 years; 49.2% female) in public and charter schools between 2021 and 2024. A validated questionnaire (Cronbach's α=0.72-0.84) assessed experimental tobacco and vaping use, social models, physical and digital exposures, and purchase attempts/denials. Analyses included bivariate tests (χ(2), Cramér's V), logistic regression for tobacco experimentation and multiple linear regression for vaping. RESULTS: Among participants, 21% had tried cigarettes and 8.3% had used e-cigarettes. Tobacco experimentation was significantly associated with having smoking friends (adjusted odds ratio, AOR=4.47; 95% CI: 3.30-6.06), smoking siblings (AOR=1.87; 95% CI: 1.32-2.64), and exposure to smoking at school (AOR=1.87; 95% CI: 1.39-2.50) or concerts (AOR=1.83; 95% CI: 1.21-2.77). Conversely, exposure at beaches or swimming pools was linked to lower odds (AOR=0.54; 95% CI: 0.36-0.82). E-cigarette use was positively associated with exposure to anti-tobacco media messages (β=0.264, p<0.001), vaping content in online videos (β=0.098, p=0.021), and having smoking friends (β=0.118, p=0.038). Each β indicates the estimated increase in the normalized vaping score per unit increase in the corresponding exposure. Additionally, being denied nicotine product purchases due to age restrictions was linked to greater odds of e-cigarette experimentation (AOR=2.87; 95% CI: 1.94-4.23). CONCLUSIONS: Τhe findings suggest that family and peer models, as well as passive exposure in both physical and digital environments, may be associated with adolescent initiation of tobacco and vaping. These associations highlight the importance of conducting further longitudinal studies to explore causal mechanisms and inform the development of effective prevention strategies tailored to adolescents' social and digital contexts.