Objective passive-smoking indicators and respiratory morbidity in young children.

Exposure to environmental tobacco smoke is associated with increased respiratory morbidity in young children, but few studies have assessed such exposure objectively by urinary cotinine measurements. 501 children aged 1-5 years, a random 5% sample of children attending an outpatient clinic, were classified as exposed or non-exposed to environmental tobacco smoke with a cut-off of 10 ng cotinine per mg creatinine in urine. Exposed children were 3.5 times (95% CI 1.56-7.90, p < 0.0024) more likely to have increased respiratory morbidity (three or more episodes during the previous 12 months) than non-exposed children after adjustment for potential confounding factors.