A total of 5,115 children had complete data on asthma, wheeze, potential confounders, NO2, and at least one SNP (4,596 with GSTP1 rs1138272, 4,748 with GSTP1 rs1695, 4,483 with TNF rs1800629); 22% were part of an intervention, 52% were male, 29% were exposed to environmental tobacco smoke in the home, 55% had parental history of atopy, and 19% were born to mothers ≥ 35 years of age. This evidence concerns the gene GSTP1 and asthma.