In this nested cohort of African American and Dominican children living in NYC, we found that that 6 day-integrated residential V, but not PM2.5, was associated with lower buccal cell promoter DNA methylation of asthma T helper (Th) gene (i.e. IL4, IFNγ) loci, even after controlling for methylation levels 6 days previously. The gene discussed is IFNG; the disease is asthma.