Evaluation of infants' exposure to environmental tobacco smoke using salivary cotinine measurements

This study aimed to determine longitudinal variations in exposure to environmental tobacco smoke (ETS) in the home among infants in Japan, and the association between infants' exposure to ETS and their living environment using salivary cotinine measurements. Data collected from 71 pairs of infants and their mothers at a general hospital over 10 months, starting 1 month after birth, were analysed using McNemer's test and Cochran's Q test as well as risk rates and 95% confidence intervals. The results showed that cotinine levels, where detected, were significantly higher in infants than in mothers living in the same household (P=0.022). The cotinine detection rates in infants who lived with smokers were significantly higher than in those who did not (risk rate=1.890) as early as 1 month after birth. These findings should therefore be communicated to smoking households to prevent ETS exposure among infants.