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- The hits may come from chemical or foreign substances that cause cancer, called carcinogens.
- These initiate the cancer process. Or the hits may be promoters that accelerate the growth of
- abnormal cells . What is critical is the number and types of hits, their frequency and their intensity.
-
- Initiators include:
- • Tobacco and tobacco smoke carcinogens. Lung cancer was a rare disease before cigarette smoking became
- widespread.
- • X-rays. It is well known that there is an increased incidence of leukemia among atomic bomb survivors. This
- same increase has been noted in radiologists, the doctors who specialize in the use of x-rays. It should be
- pointed out that the average diagnostic use of x-rays does not increase the chance of getting cancer enough to
- rule out their use as a valuable health care tool. The risk of not having an x-ray may far outweigh the risk of
- cancer being caused by the use of x-rays for diagnosis. Used properly, x-rays are of great benefit in finding
- cancer at an early, curable stage.
- • Certain hormones and drugs, such as DES , some estrogens (female hormones) and some immunosuppressive
- drugs.
- • Excessive exposure to sunlight.
- • Industrial agents or toxic substances in the environment, such as asbestos, coal tar products, benzene,
- cadmium, uranium and nickel.