9CHEMICAL RISK FACTORS
Chemical and environmental factors, including diet and lifestyle, may be responsible for causing 80 to 90 percent of all cancers. Theoretically, then, most cancers could be prevented if the factors that cause them can first be identified and then controlled or eliminated.
Throughout their lives, people are exposed to many chemicals and some drugs in small amounts and in many combinations unique to their culture and environment. Many chemicals and drugs are now known to cause human cancer, and many more are suspected carcinogens.
People who are exposed to chemicals either directly, such as those who work in the particular industry shown, or indirectly, such as firefighters exposed to burning objects made from chemicals, are at increased risk of developing the some cancer. The incidence of certain cancers in particular populations reflects prolonged low-level exposure to many carcinogens (chemical substances that cause cancer), cocarcinogens (substances that activate carcinogens), and promoting factors (substances that facilitate the action of carcinogens).