LAUSR

OBJECTIVE In an urban adolescent population, we evaluated sources of exposure to secondhand tobacco smoke (SHS), examined differences in exposure by race/ethnicity, age and sex, and determined the relationship between exposure source(s) and the biomarkers cotinine and NNAL. METHODS Participants were recruited from a public hospital-based outpatient clinic in San Francisco, CA, USA. RESULTS Of a sample of N=298 adolescents screened, 235 were biologically confirmed to be exposed to tobacco smoke. Of those, N=16 were active smokers and N=219 were exposed to SHS; 91(39%) were heavily SHS exposed (median cotinine=0.76 ng/mL) and 128 (54%) had light SHS exposure (median cotinine=0.11ng/mL). Within those SHS exposed, the most common source of exposure was in a public area. No significant racial/ethnic differences were found, although African American adolescents were more likely to live in a home that allowed smoking. Older adolescents were more likely to be exposed across several difference sources, and females more likely to be exposed in a car and in public areas. Past 7-day exposure in the home, in a car, and current blunt use were significantly related to biomarkers of exposure. CONCLUSIONS Urban adolescents are exposed to SHS across a variety of sources. Although exposure in a public area is most common, exposure in the home and in cars significantly influences tobacco biomarker levels. Interventions to reduce exposure would have the greatest impact in this population if they focused on reducing exposure in the home and in cars. History of blunt use is a strong determinant of tobacco exposure.