GSTM1 and chronic obstructive pulmonary disease: In our study, EPHX T113C C allele, GSTM1 null, GSTT1 null, GSTP1 A313G G and C341T T allele, CYP1A1 MspI C allele, SOD3 A213G G allele and L type in Ho-1 showed increased COPD risk, especially in Asians.