Nicotine Dependence in a Banned Market: Biomarker Evidence from E-Cigarette Users in São Paulo, Brazil.

Although electronic cigarettes have been banned in Brazil since 2009, their use is increasing, particularly among youth. We conducted a biomarker-based study to profile exclusive e-cigarette users in São Paulo and to examine the associations of e-cigarette use with salivary nicotine and cotinine levels. A population-based, cross-sectional study was conducted between April and September 2024 in six municipalities in São Paulo, Brazil. Randomly selected participants who reported exclusive use of electronic cigarettes completed a questionnaire and provided oral fluid samples for the determination of their nicotine and cotinine concentrations using LC-MS/MS. The cohort consisted of N = 417 participants. Significant associations were found between nicotine and cotinine concentrations and variables such as knowledge of nicotine content and product type. Addiction status significantly influenced the nicotine and cotinine concentrations, as well as smoking history, last consumption, recharge/purchase frequency, and consumption duration (all p < 0.001). Participants who perceived themselves to have a moderate or severe addiction exhibited higher nicotine and cotinine concentrations compared with those who did not perceive that they had an addiction (p < 0.001). Most participants were young, predominantly White, and highly educated and earned higher incomes. The findings reveal a correlation between perceived nicotine dependence and salivary nicotine and cotinine concentrations, underscoring the physiological and behavioral markers of electronic cigarette addiction. High salivary concentrations of nicotine appear to be independent of duration of e-cigarette use, smoking history, and age. These findings underscore the urgent need for surveillance and public health interventions, even in jurisdictions where these products remain illegal. The study limitations include its cross-sectional design and potential selection bias due to convenience sampling.