Passive smoking in asthmatic children: effect of a "smoke-free house" measured by urinary cotinine levels

Environmental tobacco smoke (ETS) decreases pulmonary function and increases both airway reactivity and frequency of child asthma exacerbations. True exposure is related not only to parents smoking and to the number of cigarettes that they smoke, but also to involuntary smoking in public places. The aim of this study was to evaluate, by measuring urinary cotinine levels, the exposure to ETS in asthmatic children and the contribution of unapparent smoke exposure. Twenty asthmatic children (aged 7-12 years) were evaluated on the 1st day (TO) and after a week (T1) in a "smoke-free house." The mean level of urinary cotinine in children was 15.8 +/- 2.7 ng/mg of creatinine at TO and 4.2 +/- 0.6 ng/mg of creatinine at T1 (p < 0.0001). The urinary cotinine concentrations were higher in children living with smoking parents (21.8 +/- 3.4 ng/mg creatinine) compared with children not exposed to parental smoke (6.8 +/- 3.0 ng/mg creatinine; p = 0.017). The number of cigarettes smoked by parents correlates with the urinary cotinine levels (p = 0.005; r = 0.64). Urinary cotinine levels significantly decreased after the avoidance of ETS in children exposed to parental smoke (21.8 +/- 3.4 ng/mg at TO; 5.0 +/- 0.8 ng/mg at T1; p < 0.001) and also in children whose parents declared to be nonsmokers (6.8 +/- 1.2 ng/mg at TO; 3.0 +/- 0.8 ng/mg at T1; p = 0.006). Our data confirm the widespread indirect and undetected tobacco smoke exposure in children with chronic asthma and the relevance of an evaluation with an objective method of the exposure to second-hand smoke.