Chemical carcinogenic factors 1. Indirect-acting chemical carcinogens: polycyclic aromatic hydrocarbons, aromatic amines and amino azo dyes, nitrosamines, fungal toxins. 2. Direct-acting chemical carcinogens: These carcinogens can cause cancer without activation in the body, such as alkylating agents and acylating agents. (1) Nitrosamines: This is a group of chemical carcinogens with strong carcinogenicity, which can cause many kinds of cancers in animals. (2) Polycyclic aromatic hydrocarbons: These carcinogens are represented by benzo(a)pyrene, which can cause skin cancer when applied to the skin of animals, and can induce sarcoma when injected subcutaneously. (3) Alkylating agents: such as mustard gas, cyclophosphamide, etc., can cause leukemia, lung cancer, breast cancer, etc.; (4) Vinyl chloride: the most widely used plastic polyvinyl chloride, which is made by the polymerization of vinyl chloride monomer. It can induce tumors in lung, skin and bone. The epidemiological survey of plastic factory workers has confirmed that vinyl chloride can cause hepatic hemangiosarcoma, and the latency period is generally more than 15 years; (5) Some metals: such as chromium, nickel, arsenic, etc. can also cause cancer. The mechanism of action of chemical carcinogens causing human tumors is very complicated. A few carcinogens can directly induce tumors after entering human body, which are called direct carcinogens; while most chemical carcinogens need to be metabolically activated or biotransformed in human body to become final carcinogens with carcinogenic activity before they can cause tumors, which are called indirect carcinogens. Tumors caused by radiation include: thyroid tumor, lung cancer, bone tumor, skin cancer, multiple myeloma, lymphoma, etc. Physical carcinogenic factors Ion radiation causes various cancers. Long-term thermal radiation also has certain carcinogenic effect, and metal elements such as nickel, chromium, cadmium and beryllium also have carcinogenic effect on human. Some clinical tumors are also related to trauma. Patients with osteosarcoma, testicular sarcoma and brain tumor often have a history of trauma. Another type of foreign body related to tumor is parasite. RNA tumor-causing viruses: Through transduction and insertional mutation, genetic material is integrated into the host cell DNA, and the host cell is transformed, and two mechanisms exist to cause cancer: (1) acute transformation virus. (2) Sexual transformation virus. (2) DNA oncogenic viruses: Commonly, human papillomavirus (HPV) is closely associated with the occurrence of human epithelial tumors, especially squamous cell carcinoma of the cervix and anal genital area. EBV virus is closely associated with Burkitt’s lymphoma and nasopharyngeal carcinoma. Epidemiological investigation of hepatitis B is closely related to hepatocellular liver cancer. Chronic gastritis caused by Helicobacter pylori is associated with the occurrence of low-grade malignant B-cell lymphoma of the stomach.