Finally, the PIAMA study has previously reported effect modification by interaction analyses for multiple TLR2 and TLR4 SNPs in the association between air pollution (using the same LUR models we presented) and childhood asthma in a subset of the PIAMA cohort (NTotal = 916; Kerkhof et al. 2010); but the current study is the first examination of GSTP1 and TNF. This evidence concerns the gene TLR4 and childhood onset asthma.