OBJECTIVE: To assess the levels of a tobacco-specific nitrosamine (NNAL) in non-smokers passively exposed to the second-hand aerosol (SHA) emitted from users of electronic cigarettes (e-cigarettes). METHOD: We conducted an observational study involving 55 non-smoking volunteers divided into three groups: 25 living at home with conventional smokers, 6 living with e-cigarette users, and 24 in control homes (smoke-free homes). We obtained urine samples from all volunteers to determine NNAL. RESULTS: We detected NNAL in the urine of volunteers exposed to e-cigarettes (median:0.55 pg/mL; interquartile range: 0.26-2.94 pg/mL). The percentage of urine samples with quantifiable NNAL differed significantly among the three groups of homes: 29.2%, 66.7% and 76.0%, respectively (p=0.004). CONCLUSIONS: We found NNAL nitrosamine in urine samples from people exposed to SHA from e-cigarettes. However, these results could be confirmed with more studies with larger sample sizes.