Passive smoking and impaired lung function in cystic fibrosis.

Passive smoking was measured in 57 children with cystic fibrosis and in 51 controls using a questionnaire and a measurement of urinary cotinine concentration. In the cystic fibrosis group, cotinine was significantly lower than in the controls. Also in this group, when the parents smoked the child's forced expiratory volume in one second decreased by 4% and the forced vital capacity by 3% for every 10 cigarettes smoked in the household each day.