Assessment of exposure to secondhand smoke by questionnaire and salivary cotinine in the general population of Barcelona, Spain (2004-2005)

Objectives: To estimate the prevalence of self-reported exposure to secondhand smoke (SHS) in different settings and to describe salivary cotinine concentration and its determinants among non-smokers. Methods: Cross-sectional study of a representative sample (N = 775) of adult non-smokers in Barcelona, Spain (years 2004-2005). We assessed exposure to SHS using a questionnaire and measurement of salivary cotinine concentration. We calculated prevalence rates of self-reported exposure and medians and geometric means of salivary cotinine concentration. We adjusted for potential confounding factors with multinomial logistic regression models. Results: The prevalence rate of self-reported exposure to SHS among non-smokers in any setting was 75.7% (95% CI: 72.7%-78.8%). The prevalence of exposure to SHS tended to decrease with age. The geometric mean of cotinine concentrations among non-smokers was 1.49 ng/ml (95% CI: 1.39-1.60 ng/ml) among all subjects, and 1.80 ng/ml (95% CI: 1.37-2.35 ng/ml) in subjects who reported exposure to SHS in all settings. In bivariate and multivariate analyses, the cotinine concentration increased with the number of smokers and the number of cigarettes smoked per day in the presence of non-smokers in the household. Conclusions: In this population, self-reported exposure to SHS is very high. Salivary cotinine concentrations in non-smokers are associated with exposure at home.