A semi-quantitative analysis was performed in a blinded fashion (by authors LF and ML) on ALDH3A1 expression in lung resection material of 5 COPD patients (current smokers), 5 COPD patients (ex-smokers), 5 healthy controls (current smokers), and 5 healthy never/ex-smokers (Table S5 in File S1). This evidence concerns the gene ALDH3A1 and chronic obstructive pulmonary disease.