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Quick Facts

Risk Factors for Cancer


The Manual's Editorial Staff

Last full review/revision Sep 2019| Content last modified Sep 2019
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A risk factor is something that gives you a higher chance (risk) of getting a certain disease.

  • If you have a risk factor for cancer, it means you're more likely than the average person to get cancer

  • However, having a certain risk factor doesn’t mean that you'll get cancer

Risk factors for cancer include:

  • Having certain genes (traits you inherit from your parents and grandparents)

  • Being around certain chemicals at work or in the environment

  • Eating or drinking certain things

  • Being exposed to radiation

  • Having certain infections

Carcinogens are things that sometimes cause cancer. Usually, your risk of cancer is higher if you're exposed to more of a carcinogen or you're exposed for a longer time.

What are genetic risk factors for cancer?

Each of your body's cells contains genes. Genes are the instructions that tell each of your cells what to do. Genes tell cells when to grow, when to stop growing, and what substances to make. For example, certain genes tell cells in your stomach to make stomach acid.

Sometimes one of your genes can go bad in ways that make a cell turn cancerous. A gene can go bad if:

  • The gene was damaged by something you were exposed to (an environmental factor)

  • The gene was copied incorrectly during normal cell growth

Less likely, you inherited a cancer gene from one of your parents. Sometimes people in a family are more likely to have a certain cancer. A cancer-causing gene could run in that family. One cancer-causing gene called BRCA increases the risk of breast cancer.

What are environmental risk factors for cancer?

Being around certain things can raise your chances of cancer, including:

  • Tobacco smoke: Lung, mouth, throat, esophagus, kidney, and bladder cancers

  • Asbestos (a mineral fiber used for insulation and other building materials): Lung cancer and mesothelioma (cancer in the tissues that line your lungs)

  • Sunlight: Skin cancer

  • X-rays: Leukemia and cancer in the organ exposed to radiation

  • Radon (a radioactive gas that comes from the ground and can build up to harmful levels in basements): Lung cancer

Some chemicals used at work (such as benzene, chromates, nickel, certain pesticides, and vinyl chloride) can cause cancer.

Geography (where you live) can affect your chances of getting cancer. One reason is that people in different areas may be exposed to different amounts of carcinogens. Another reason is that people in different areas may have different genetic risk factors.

What are other risk factors for cancer?

Your age:

  • More than half of cancers happen in people older than 65 because older people have been exposed longer to carcinogens (things that can cause cancer)


Just being overweight or obese can raise your risk of breast, uterus, colon, kidney, and esophagus cancer.

Certain medicines:

  • Estrogen and diethylstilbestrol (DES): Breast cancer

  • Some drugs to treat cancer actually increase your risk of developing another cancer later on

Radiation exposure, either on purpose for medical reasons or accidentally:

  • From medical tests (x-rays, CT scan) or radiation therapy

  • Accidental exposure to radioactive material or nuclear radiation from a power plant accident

Infections with certain viruses and bacteria:

Inflammatory disorders (long-term inflammation of certain organs) may increase risk of cancer:

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