Cancer Causes

Diet and lifestyle
There are over 200 different types of cancer. We don't know the causes for each one of these cancers, but we do know about some. It is important to note that for many cancers, there may be more than one cause.
One of the biggest risks is increasing age. Cancer can occur at any age but the risk of developing it increases with age. Nearly two thirds (64%) of people who get cancer are over the age of 65, and more than a third are over 75.
We make lifestyle choices everyday - some we know increase our risk of developing cancer, others may have an influence on our risk. For example, smoking is a major cause of lung cancer and is a factor in other cancers, such as bladder cancer and cancers of the head and neck. Other factors that can influence our risk of developing cancer include heavy alcohol consumption and exposure to sunlight.
It is also thought that diet can influence the development of some cancers, although the evidence is less clear. Diets high in animal fats have been linked with breast cancer, bowel cancer and prostate cancer. A diet that is low in fresh fruit and vegetables may also increase your risk of developing some types of cancer. Obesity has been linked to some cancers, such as cancer of the breast or kidney.

Environmental and occupational causes
Contact with certain harmful substances in the environment or workplace can cause cancer. Substances that are known to cause cancer are called carcinogens.
We know, for example, that 9 out of 10 people who develop mesothelioma (a rare type of cancer affecting the linings of the lung and abdomen) have had contact with asbestos. People who have worked in industries such as ship-building and construction may have come into contact with asbestos. Its use is now banned in the UK.
Certain chemicals used in dye factories, rubber production, gas works and other chemical industries have all been linked to bladder cancer. Fortunately these chemicals have now been banned.
Environmental causes include natural radiation, for example, from the sun. We know that most skin cancers, including melanoma, are caused because of prolonged exposure to the sun. Naturally occurring radon gas has also been linked to some types of cancer, namely lung cancer.
Viruses
It is important to remember cancers are not infectious and cannot be caught from someone. However, there are a number of different viruses that are thought to be contributing factors in the development of cancer.
For example, exposure to HPV (human papilloma virus) is known to increase the risk of developing some types of cancer. For further information about this, see the section about HPV.
Other viruses include the Epstein-Barr virus, which is linked to some types of lymphoma.
There is also a bacterial infection known as H-pylori which is linked to a rare type of stomach cancer.