GSTP1 and chronic obstructive pulmonary disease: The GSTM1, GSTT1 null, and GSTP1 Val/Val have been linked with increased risk (12-fold) for COPD [17] and GSTT1 deficiency in combination with GSTM1 deficiency independently appears to be associated with an accelerated age-related decline of lung function in males irrespective of smoking [18].