Cocarcinogens

15. Cocarcinogens

Whether found in polluted urban air, in cigarette smoke, or in some products derived from coal tar and petroleum, environmental carcinogens usually occur in a complex mixture. The mixture of chemicals can multiply the risk of cancer that would be encountered with one carcinogen alone. For example, although 75 to 85 percent of lung cancers are related to smoking, particularly cigarettes, atmospheric pollution and some occupational exposures appear to exacerbate the risk. According to one calculation, asbestos workers who are nonsmokers contract lung cancer at normal rates, but a cigarette smoker who works with asbestos has eight times the risk of dying of lung cancer as similar smokers of the same age who do not work with asbestos and 92 times the risk of laborers who neither work with asbestos nor smoke.