The exact reason why a person develops cancer is unknown. But we do know some of the things that cause or influence the risk of getting cancer. We call these "risk factors."

You can reduce your risk of getting cancer by making positive lifestyle decisions. Not smoking, eating a healthy diet, and staying physically active are some of the ways you can do it.

But there are some risk factors you cannot control. Age is a risk factor for cancer. 63% of people who develop cancer—more than 3 out of every 5 people—are over 65.

Making changes in your lifestyle is no guarantee that you will not develop cancer. Cancer happens because of many different factors, many of which are out of our control.

This makes checking your body and participating in cancer screening programs really important for everyone. Your GP can give you more information about national cancer-screening programs as well as advice on lowering your risk of cancer.


Does my occupation or environment affect my risk of cancer?

Contact with certain harmful substances in the natural environment or the workplace can cause cancer. Substances that are known to cause cancer are called carcinogens.


Asbestos is a natural mineral that can cause damage to the lungs. Nine out of every ten people who develop mesothelioma (a rare type of cancer that affects the lining of the lungs and abdomen) have come into contact with asbestos. People who have worked in industries such as shipbuilding and construction may have come into contact with asbestos.

Other occupational causes of cancer

Certain chemicals used in dye factories, rubber production, gas works, and other chemical industries have been linked to bladder cancer. Fortunately, these chemicals have been banned.

Environmental causes of cancer

One of the main environmental causes of cancer is natural radiation, such as radiation from the sun. We know that most skin cancers are caused by prolonged exposure to the sun.


Some types of cancer are more likely to affect people who have immune problems.

People with lower immunity may have:

had a previous organ transplant and are taking immune suppressants to prevent the organ from rejection by the body

reduced immunity caused by HIV (human immunodeficiency virus)

rare medical conditions that lower immunity.

People with deficient immune systems are more likely to develop lymphomas and certain types of skin cancer (particularly non-melanomas). They are also at greater risk of cancers that are influenced by viruses or bacteria such as cervical cancer, some types of anal and genital cancers, and some cancers of the stomach and liver.


It is important to remember that cancer isn't contagious. However, there are a number of different viruses that are believed to influence the development of cancer.

These can cause gene-level changes in the cells, making them more likely to become cancerous.

One of the most common viruses that can affect the risk of cancer is the human papilloma virus (HPV). This increases the risk of developing cancer of the cervix, head and neck cancer, and cancers of the anal or genital area.

Other viruses that are linked to the development of cancer are:

Epstein-Barr virus, which is linked to some types of lymphoma

Hepatitis B and C viruses that are linked to primary liver cancer

T-cell leukemia virus that is lined to T-cell leukemia in adults

There is also a bacterial infection known as H-pylori, which is linked to a rare type of stomach cancer.

Keep in mind that not everyone who is infected with one of these viruses or bacteria will develop cancer.


The human papilloma virus (HPV) affects the skin and the mucosa. The mucosa is the moist membrane that lines the inside of certain body parts. Some of these parts include the mouth, throat, and anus.

It is very common, and more than 100 different types of HPV have been identified.

Certain types of HPV may increase the risk of developing cancer. These are called high-risk HPVs. But it is important to keep in mind that most people with HPV do not develop cancer.

HPV is transmitted through skin contact, often during sexual intercourse. Barrier forms of contraception can lower your risk of infection. For most people, HPV infections come and go without any symptoms. Sometimes, the virus can remain inactive for months after infection.

HPV is associated with:

  • cervical cancer
  • vulval cancer
  • vaginal cancer
  • anal cancer
  • head and neck cancers
  • penis cancer.

There is no standard test for HPV. HPV cannot be diagnosed by having a blood test. HPV infection of the cervix can be diagnosed in women as a result of a cervical screening program.