[Passive smoking in children. Its detection by the assay of urinary cotinine]

Passive tobacco smoking is responsible for increased respiratory morbidity in young children. This point is not always understood by parents and the use of a sensitive marker for nicotine exposure may help them to smoke less.

Urinary cotinine concentration was measured in 72 children, aged from 1 to 5 years, that had been admitted to our unit during October and November 1991 for various causes. The results were correlated with the smoking habits of their parents. Urine samples were obtained during the first hours after admission and the cotinine concentration was measured by HPLC. Concentrations > 5 micrograms per liter were considered to be positive.

A total of 67 urine samples were analysed: 43 (64.2%) were positive with cotinine concentrations of 5 to 77 micrograms/l (mean: 19.7). Both parents of 21 children were smokers; the fathers of 18 children and the mothers of 11 children, alone, smoked. There was therefore at least one smoker in the environment of 50 children. There was a highly positive correlation between parental smoking and urinary cotinine (p < 0.0001). For the infants with only one parent who was a smoker, their urinary cotinine was higher when the smoker was the mother rather than the father.

An urinary cotinine of > 6 micrograms per liter is a precise, sensitive, test for passive smoking in young children. This test is well accepted by families and its result may persuade parents to stop or moderate their use of tobacco. This test also could be used, as part of a pulmonary check-up, as a public health indicator.