目前认为2/3以上人类癌瘤与外环境因素有关。资料表明近年来由于工业迅速发展,环境污染日益严重,肺癌发病率不断增加。美国从40年代至70年代,男性肺癌死亡率提高了18倍。环境致癌物中约80～90％为化学物质。迄今,已有1000余种化学致癌物质已由动物试验证实。 化学致癌物的作用可分为二类:一类是能直接引起人和动物癌的化学物质称为直接致癌物;一类需通过体内代谢转化过程或激活后才能起致癌作用的称为前致癌物。另一类本身单独不能致癌,但能促进致癌物质起致癌作用的称促癌物。环境中化学致癌物质主 At present, it is believed that more than two-thirds of human cancers are related to external environmental factors. The data shows that due to the rapid development of industry in recent years, environmental pollution has become increasingly serious and the incidence of lung cancer has continued to increase. In the United States from the 1940s to the 1970s, male lung cancer mortality increased by 18 times. About 80 to 90% of environmental carcinogens are chemical substances. To date, more than 1,000 chemical carcinogens have been confirmed by animal experiments. The role of chemical carcinogens can be divided into two categories: one is a chemical that can directly cause human and animal cancers called direct carcinogens; the other is known as pre-carcinogenesis, which requires oncogenic transformation or activation before it can cause cancer. Things. The other category alone cannot cause cancer, but it can promote cancer-causing substances called carcinogens. Chemical carcinogens in the environment