EPHX1 and chronic obstructive pulmonary disease: In our study of individual SNPs in EPHX1 (the exon-3 Tyr113His and exon-4 His139Arg variants), the homozygous minor Thr113His variant showed only a borderline association with the COPD phenotype (P = 0.095), however the level of association was further reduced when the model was adjusted for age, sex and pack-years.