Especially for RET/PTC rearrangements in genes, some environmental agents such as benzene (in cigarette smoke and automobile exhaust), diethylnitrosamine (DEN) (in cigarette smoke, pesticides, and treated meat), and chemotherapeutic drugs can significantly increase fragile site breakage, and so these pollutants are positively associated with the risk of thyroid cancer [100,101]. The gene discussed is RET; the disease is thyroid cancer.