CYP1A1 and lung cancer: Thus, we speculated that the interaction between CYP1A1 or GSTM1 polymorphisms and lung cancer is related to polycyclic aromatic hydrocarbons exposure derived from smoking because polycyclic aromatic hydrocarbons are primarily metabolized by CYP1A1 and GSTM1. The greater effects observed among smokers support the smoking-related etiology of lung cancer in Chinese population.