RT Journal Article SR Electronic T1 Genetic polymorphism of GSTM1 and antioxidant supplementation influence lung function in relation to ozone exposure in asthmatic children in Mexico City JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 8 OP 10 VO 59 IS 1 A1 I Romieu A1 J J Sienra-Monge A1 M Ramírez-Aguilar A1 H Moreno-Macías A1 N I Reyes-Ruiz A1 B Estela del Río-Navarro A1 M Hernández-Avila A1 S J London YR 2004 UL http://thorax.bmj.com/content/59/1/8.abstract AB Background: We recently reported that antioxidant supplementation with vitamins C and E mitigated ozone related decline in forced expiratory flow (FEF25–75) in 158 asthmatic children in an area with high ozone exposure in Mexico City. Methods: A study was undertaken to determine whether deletion of glutathione S-transferase M1 (GSTM1 null genotype), a gene involved in response to oxidative stress, influences ozone related decline in FEF25–75 and the benefit of antioxidant supplementation. Results:GSTM1 null children receiving placebo had significant ozone related decrements in FEF25–75 (percentage change per 50 ppb of ozone 2.9 (95% CI −5.2 to −0.6), p = 0.01); GSTM1 positive children did not. Conversely, the effect of antioxidants was stronger in children with the GSTM1 null genotype. Conclusions: Asthmatic children with a genetic deficiency of GSTM1 may be more susceptible to the deleterious effects of ozone on the small airways and might derive greater benefit from antioxidant supplementation.