Normal cells in the tumor is the body in different initiating and promoting factors produced under long-term proliferation and abnormal differentiation to form new organisms. Cause of cancer is very complex and not yet completely understood. The current environment and that the tumor is the result of interaction between host and external factors.
It is estimated that about 80% of the cancer and environmental factors. All factors which affect cancer and cancer-promoting factor nothing more than the same time, the body's internal factors in tumor occurrence and development also plays an important role, such as heredity (genetic susceptibility) endocrine and immune mechanisms. In which the tumor carcinogens – chemical factors are the following:
(1) alkylating agents: biological function similar to the X-rays, carcinogenic transformation, mutations and deformities, which is characterized with the role of alkylation, it is in direct contact with the organization works, without first activation, so called direct carcinogen, and its activity large. but it is itself vulnerable to inactivation in the environment, so there is little risk. Often used in chemotherapy, pesticides and enzyme inactivation agent. Such as nitrogen mustard, sulfur mustard, organic pesticides, mites ethyl alcohol, can cause lung cancer and hematopoietic tumors.
Cancer causing factors – chemical factors (2) polycyclic aromatic compounds: it is a condensation of several aromatic hydrocarbons, insoluble in water content in fat and organic solvents, such as coal tar 3 , 4 – benzopyrene, are found in soot, dirt, car exhaust, cigarette smoke, smoked fish, not exactly burn fat, burning coal, oil, etc., it does not directly cause cancer. and subject to activation in order to cause cancer. Such as laboratory use synthetic methylcholanthrene, 1, 2, 5, 6 – diphenyl and anthracene, frequent contact with skin cancer and workers easily lung cancer .
(3) amino azo dyes: amino azo dyes containing azo groups of these compounds-N = N A. As textiles, food and beverage dyes, additives, amino azo dyes to the scarlet rabbits injected, can cause epidermal hyperplasia. An important part of the scarlet o-amino azo toluene eleven rats fed or injected, can cause liver weight of small liver cancer. Use butter yellow (4 – dimethylamino azobenzene) long-term fed rats, but also can cause liver cell carcinoma. Amino azo carcinogens are characterized by long-term administration of large doses can be carcinogenic, cancer away from the route of administration and other organs such as liver and bladder.
Cancer causing factors – chemical factors (4) nitrite Gum: These compounds are widespread in the environment easily from precursors in the formation. Nitroso compounds are important environmental chemical carcinogens, a number of natural food in the human nitrosamines, especially in fish and cured meat products for more. In addition, human exposure through food outside the synthesis of nitrosamines, nitroso compounds can also be present in the environment from the precursor synthesized in the body. Nitrosamines and esophageal cancer, gastric cancer and liver cancer occurrence.
(5) mycotoxins: Mycotoxins are naturally occurring carcinogens, 60 years of the 20th century the carcinogenicity of aflatoxin found in some fungi and microorganisms that metabolites are carcinogenic. 40 kinds of microbial metabolites produced by the detection of carcinogenic activity of the main mycotoxins, most of which are produced by the fungi in the environment. In these fungal toxins, there are several of animal cancer can also lead to human tumors. Mycotoxins are natural contaminants often. Contaminated food into the body of human cancer. Such as aflatoxin contaminated food can cause liver cancer, also can cause kidney, stomach and colon adenocarcinoma.
(6) Plant toxins: plant toxins such reports since 1950, Cook has been the carcinogenicity of plant alkaloids. People nearly a hundred kinds of naturally occurring compounds of plant origin, and 40 kinds of crude plant extracts were carcinogenic activity The test results showed that: more than half of the compounds and extracts are carcinogenic. Such as: Cycads factors may cause the animal liver, fern toxins can cause stomach, intestines, bladder cancer, etc., safrole can cause liver and esophagus cancer.
Cancer causing factors – chemical factors (7) Other: Metallic elements are carcinogenic to humans, such as nickel, chromium can cause lung cancer; non-metallic elements and organic compounds are also carcinogenic, such as arsenic can induce skin cancer; vinyl chloride can induced human liver angiosarcoma. Anhui DDT, benzene, are likely to cause liver cancer .