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Causes of Cancer

How Cancer is Caused?

Cancer is caused by accumulated damage to genes. Such changes may be due to chance or to exposure to a cancer causing substance. Cancer is caused by changes (mutations) to the DNA within cells.

The substances that cause cancer are called carcinogens. A carcinogen may be a chemical substance, such as certain molecules in tobacco smoke. The cause of cancer may be environmental agents, viral or genetic factors.

We should bear in mind, though, that in the majority of cancer cases we cannot attribute the disease to a single cause.

Gene Mutation

  • Gene mutations you're born with. You may be born with a genetic mutation that you inherited from your parents. This type of mutation accounts for a small percentage of cancers.

  • Gene mutations that occur after birth. Most gene mutations occur after you're born and aren't inherited. A number of forces can cause gene mutations, such as smoking, radiation, viruses, cancer-causing chemicals (carcinogens), obesity, hormones, chronic inflammation and a lack of exercise.

We can roughly divide cancer risk factors into the following groups:

1. Biological or internal factors, such as age, gender, inherited genetic defects and skin type.

Bacteria and viruses can cause cancer:

  • Helicobacter pylori (H. pylori, which causes gastritis)

  • HBV, HCV (hepatitis viruses that cause hepatitis)

  • HPV (human papilloma virus, papilloma virus, which causes changes eg. Cervical cells)

  • EBV (Epstein-Barr virus, the herpes virus that causes inflammation of the throat lymphoid)

2. Environmental exposure, for instance to radon and UV radiation, and fine particulate matter.

Radiation can cause cancer:

  • ionising radiation (e.g. X-ray radiation, soil radon)

  • non-ionised radiation (the sun’s ultraviolet radiation)

3. Occupational risk factors, including carcinogens such as many chemicals, radioactive materials and asbestos.

Cancer causing factors related to work and living environments include:

  • asbestos fibres

  • tar and pitch

  • polynuclear hydrocarbons (e.g. benzopyrene)

  • Some metal compounds

  • Some plastic chemicals (e.g. Vinyl chloride)

4. Lifestyle-related factors.

Lifestyle-related factors that cause cancer include:

  • tobacco

  • alcohol

  • UV radiation in sunlight

  • some food-related factors, such as nitrites and poly aromatic hydrocarbons generated by barbecuing food).

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