Fine Particle, Ozone Exposure, and Asthma/Wheezing: Effect Modification by Glutathione S-transferase P1 Polymorphisms

BACKGROUND: There are limited studies on the role of interaction between exposure to ambient air pollution and glutathione-S-transferase (GST) P1 on the risk of asthma/wheezing among children, which provided suggestive, but inconclusive results. METHODS: To assess the joint effect of air pollutants and GSTP1 on asthma/wheezing, we conducted a nationwide cross-sectional study of 3,825 children in Taiwan Children Health Study. The studied determinants were three GSTP1 Ile105Val (rs 1695) genotypes (Ile-Ile; Ile-Val and Val-Val) and expoure to ambient air pollutants. We used routine air-pollution monitoring data for ozone (O(3)) and particles with an aerodynamic diameter of 2.5 µm or less (PM(2.5)). The effect estimates were presented as odds ratios (ORs) per interquartile changes for PM(2.5) and O(3). FINDINGS: In a two-stage hierarchical model adjusting for confounding, the risk of asthma was negatively associated with PM(2.5) (adjusted odds ratio (OR) 0.60; 95% confidence interval (CI) 0.45, 0.82) and O(3) (OR 0.74; 95% CI 0.60, 0.90) among Ile105 homozygotes, but positively associated with PM(2.5) (OR 1.52; 95% CI 1.01, 2.27) and O(3) (OR 1.19; 95% CI 0.91, 1.57) among those with at least one val105 allele (interaction p value = 0.001 and 0.03, respectively). A similar tendency of effect modification between PM(2.5) and O(3) and GSTP1 on wheezing was found. CONCLUSION: Children who carried Ile105 variant allele and exposed to PM(2.5) and O(3) may be less likely to occurrence of asthma/wheezing.