CYP1A1 and chronic obstructive pulmonary disease: The variations in structure and function of CYP1A1 on account of MspI and Ile/Val polymorphisms might result in altered CYP1A1 enzyme activity and different rate of procarcinogens metabolism like PAHs [10], nitrosamines, and aromatic amines [19], thus generating individual's risk difference when exposed to environmental COPD inducers.