**7.1 Chemical carcinogenesis**

Sir Percival Pott (London surgeon) first related scrotum skin cancer in the chimney sweeps to a specific chronic chemical exposure to soot. Based on this, a rule was made that chimney sweep members must bathe daily and this public health measure controlled scrotal skin cancer. Japanese investigators (Yamagiva and Ichikawa) experimentally produced skin cancers in rabbits by using coal tar. Subsequently, hundreds of chemical carcinogens were discovered (**Table 7**).

#### **7.2 Direct-acting agents**

Direct-acting chemical agents do not require metabolic conversion to become carcinogenic, but most of them are weak carcinogens. Some of the drugs (e.g., alkylating agents) are used to cure, control, or delay recurrence of some cancer (e.g., leukemia, lymphoma) and may produce a second form of cancer (e.g., acute myeloid leukemia) later.
