Passive smoke exposure in infants and children with respiratory tract diseases.

1. The adverse effect of passive smoke exposure on the respiratory tract, particularly in infants and children, is not an issue of dispute. It was the objective of this study to analyse the extent and the intensity of passive smoke exposure in infants and children with respiratory tract diseases, and compare the information obtained with parents' subjective assessment. At the time of admission to the hospital, the parents of 295 infants and children (aged 1 month to 11 years) were questioned by the physician as to the smoking habits in the families' homes. An HPLC method was employed to determine simultaneously nicotine, cotinine and trans-3'-hydroxycotinine in the children's urine. 2. The sum of the nicotine metabolites turned out to be a sensitive marker in determining passive smoke exposure. Measurements revealed passive smoke exposure in 66% of the children, the frequency in younger children being significantly (P < 0.001) higher than in children over 5 years (84% vs 52%). The average concentration of nicotine metabolites in younger passive smokers was significantly (P < 0.001) higher when compared to the older ones (193 nmol/l vs 86 nmol/l). Forty-nine per cent of the parents assessed that their children had experienced passive smoke exposure, and another 10% emphasised that they only smoked in the absence of their child. In children with cystic fibrosis and bronchial asthma, the number of passive smokers as assessed by their parents were lower by 65% and 29% respectively when compared to the findings obtained from measurements. In children without respiratory diseases, the difference was as little as 18%. 3. Parents when questioned in conjunction with an illness of their children, tended to understate, or even withhold the truth about, passive smoke exposure. Therefore, reliable information on passive smoke exposure of patients can only be obtained through objective measurements.