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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.

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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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