Passive cigarette smoke exposure of infants: Importance of nonparental sources

Objective: To learn whether cigarette smoking by persons other than parents significantly contributes to the passive environmental tobacco smoke (ETS) exposure of infants. Study Design: A cohort of infants prospectively followed up from birth to age 2 years with monthly questionnaires concerning smoking by different categories of adults coming into contact with the infants. Setting: Health maintenance organization members residing in several suburban communities of Detroit, Mich, defined by contiguous ZIP codes. Subjects: Ninety-seven (83%) of 117 healthy, full-term infants, thought to be at high risk of allergic disease based on cord blood IgE, who were born to eligible mothers and who completed 24 months of follow-up. Main Outcome Measures: Average of bimonthly urinary cotinine-creatinine ratios (CCRs) during the 2 years of the study. Results: There were significant correlations (r≤0.28, P≤.005) between the frequency of smoking by all 7 categories of adults considered and the average CCRs of the infants. Multivariable analysis demonstrated that average urinary CCRs were significantly associated not only with smoking by the infant's parents, but also with smoking by workers at day care away from the home, persons visited away from the home, and persons other than parents residing in the home (overall R²=0.72, P=.001). Conclusions: Smoking by multiple individuals, other than the parents, significantly contributes to the ETS exposure of infants. These findings suggest that, at least for infants, efforts to reduce the adverse health effects of ETS exposure should extend beyond curtailing parental smoking.