Fig. 1. Flow chart of the study population. Of infants with prenatal indoor PM2.5 measurements (n=608), 14 met the exclusion criteria, 72 were withdrawn from the study, and 11 were lost to follow-up. An additional 204 infants were then excluded because the RTIs, prenatal ETS exposure, or genotype data were missing. ETS, environmental tobacco smoke; PM2.5, fine particulate matter; RTIs, respiratory tract infections.
