The association between prevalence of asthma and NO2 was significant for subjects homozygous for the major allele of NQO1 rs2917666 (OR = 1.54; 95% CI, 1.10–2.24) and for TNFA rs2844484 (OR = 2.02; 95% CI, 1.30–3.27). Here, TNF is linked to asthma.