EPHX1 and chronic obstructive pulmonary disease: Genetic correlation case-control studies have shown that EPHX1 rs1051740 genetic variations increased the risk of COPD (Hersh et al., 2005; Hersh et al., 2006; Hersh et al., 2007), whereas EPHX1 rs2234922 variation decrease the risk of COPD (Smith and Harrison, 1997).