A carcinogen is something (chemical, radiation, etc) that can damage a cell and make it more likely to turn into a cancerous cell. As a general rule, the more the exposure to a carcinogen, the greater the risk. Well known examples of carcinogens include:
Smokers are more likely to developlung cancer, mouth cancer, throat cancer, oesophageal cancer, bladder cancer and pancreatic cancer..Smoking is thought to cause about aquarter of all cancers. About 1 in 10 smokers die from lung cancer. The heavier you smoke, the greater the risk. If you stop smoking, your risk goes down considerably.
Chemicals such as asbestos, benzene, formaldehyde, etc. If you have worked with thesewithout protection you have an increased risk of developing certain cancers. For example, a cancer called mesotheliomais linked to past exposure to asbestos.
The older you become, the more likely you will develop a cancer. This is probably due to an accumulation of damage to cells in the body over time. Also, the body's defences against abnormal cells may become less good as you become older. For example, the ability to repair damaged cells, and the immune system which may destroy abnormal cells, may become less efficient with age. So, eventually one damaged cell may manage to survive and multiply out of control into a cancer. Most cancers develop in older
Diet and other lifestyle factors can alter the risk of developing cancer. For example:
If you eat a lot of fruit and vegetables you have a reduced risk of developing certain cancers. The exact way in which they protect against cancer is not fully understood. These foods are rich in vitamins and minerals, and also contain chemicals called antioxidants. They may protect against damaging chemicals that get into the body. We should all eat at least five portions of fruit and vegetables per day (some experts recommend even more).
Eating too much fatty food possibly increases the risk of developing certain cancers.
The risk of developing certain cancers is increased by obesity, lack of regular exercise (physical activity), and drinking a lot of alcohol.
For example, one large research study (cited below) followed up over 55,000 people for 10 years. It looked at lifestyle factors and rates of cancer. The study concluded that by following recommendations on keeping physically active, keeping weight in check, not smoking, drinking alcohol in moderation and having a healthy diet, the risk of developing bowel cancer could be reduced by as much as 23%. But, the study found that even improvement in some of these lifestyle factors had some reduction in risk.
Radiation is a carcinogen. For example, exposure to radioactive materials and nuclear fallout can increase the risk of developing cancer of the blood cells (leukaemia) and other cancers. Too much sun exposure and sunburn (radiation from UVA and UVB) increase the risk of developing skin cancer. The larger the dose of radiation, the greater the risk of developing cancer. But note: the risk from small doses such as from a single X-ray test, is very small.
Some viruses are linked to certain cancers. For example, people with persistent infection with the hepatitis B virus or the hepatitis C virus have an increased risk of developing cancer of liver. Another example is the link between the human papillomavirus (HPV) and cervical cancer . Most (possibly all) women who develop cervical cancer have been infected with a strain (subtype) of HPV at some point in their lives. However, most viruses and viral infections are not linked to cancer.
People with a poor immune system have an increased risk of developing certain cancers. For example, people with AIDS, or people on immunosuppressive therapy.
Your genetic 'makeup'
Some cancers have a strong genetic link. For example, in certain childhood cancers the abnormal gene or genes that may trigger a cell to become abnormal and cancerous (malignant) are inherited. Other types of cancer may have some genetic factor which is less clear-cut. It may be that in some people their genetic 'makeup' means that they are less resistant to the effect of carcinogens or other factors such as diet.