What Causes Cancer?

Cancer is a complex group of diseases with many possible causes. In this section you can learn more about the known causes of cancer, including genetic factors; lifestyle factors such as tobacco use, diet, and physical activity; certain types of infections; and environmental exposures to different types of chemicals and radiation.

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Genetics and Cancer

Some types of cancer run in certain families, but most cancers are not clearly linked to the genes we inherit from our parents. In this section you can learn more about the complex links between genes and cancer, as well as genetic testing and how it is used.

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Tobacco and Cancer

In this section you can get information on cigarette, cigar, and smokeless tobacco use, and learn how it affects different groups of people.

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Diet and Physical Activity

Get the facts on how diet, physical activity, excess body weight, and alcohol use may affect your risk of cancer.

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Sun and UV Exposure

In this section you can learn more about the link between too much sun exposure and cancer.

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Other Carcinogens

Learn about some of the environmental causes of cancer that may lurk in our homes, at work, in pollution, and even in some medical tests and treatments. You can also learn how some types of infections are linked to cancer.