Urinary cotinine concentrations in preschool children showed positive associations with smoking fathers.
This study aimed to test the association between fathers' smoking behaviour and urinary cotinine levels among preschool children exposed to environmental tobacco smoke (ETS). Possible factors influencing this association were also explored. We recruited 368 smoking fathers with children aged five to six from five preschools in the city of Changsha, China. Urine samples were collected from the children, and the fathers were interviewed face-to-face. We adjusted for potential confounding factors with linear regression models. The geometric mean of the cotinine concentration in the children's urine was 3.94 ng/mL (95% confidence interval 3.71-4.22). In multivariate analyses, the important predictors of urinary cotinine levels among children, after adjusted confounding factors, were the number of cigarettes smoked in front of the children at home per day (B = 0.414, p < 0.001), the number of cigarettes smoked by the father in front of the children at home (B = 0.105, p < 0.001) and the mean duration of the children's exposure to ETS at home (B = 0.111; p = 0.046). Urinary cotinine concentrations of children exposed to ETS at home were positively associated with smoking fathers and smoking behaviours and the mean duration of ETS exposure at home. Targeted interventions are urgently needed to reduce children's exposure.