Fu et al. (2012) found high NO2 exposures associated with more severe asthma in children with high beta-2-adrenergic receptor (ADRB2) gene methylation. In a cross-sectional study, Belanger et al. (2006) found that measured NO2 concentrations had a significant positive association with increased likelihood of wheeze and chest tightness among asthmatic children in multi-family housing, but not in single-family housing. In adults, a prospective study (Ng et al. 2001) found adverse respiratory effects in asthmatic women associated with cooking-related measured NO2 exposures. Here, ADRB2 is linked to asthma.