Answer ( 1 )

  1. Cancer is caused by accumulated damage to genes. Such changes may be due to chance or exposure to a cancer-causing substances.

    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.

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

    biological or internal factors, such as age, gender, inherited genetic defects and skin type
    environmental exposure, for instance to radon and UV radiation, and fine particulate matter
    occupational risk factors, including carcinogens such as many chemicals, radioactive materials, and asbestos
    lifestyle-related factors.
    Lifestyle-related factors that cause cancer include:

    The UV radiation in sunlight
    some food-related factors, such as nitrites and polyaromatic hydrocarbons generated by barbecuing food).
    Lifestyles can prevent cancer

    Cancer-causing factors related to work and living environments include:

    asbestos fibers
    tar and pitch
    polynuclear hydrocarbons (e.g. benzopyrene)
    Some metal compounds
    Some plastic chemicals (e.g. Vinyl chloride)
    Bacteria and viruses can cause cancer:

    Helicobacter pylori (H. pylori, which causes gastritis)
    HBV, HCV (hepatitis viruses that cause hepatitis)
    HPV (human papillomavirus, papillomavirus, which causes changes eg. Cervical cells)
    EBV (Epstein-Barr virus, the herpes virus that causes inflammation of the throat lymphoid)
    Radiation can cause cancer:

    ionizing radiation (e.g. X-ray radiation, soil radon)
    non-ionized radiation (the sun’s ultraviolet radiation)
    Some drugs may increase the risk of cancer:

    certain antineoplastic agents
    certain hormones
    medicines that cause immune deficiency
    In 5 – 10 percent of breast cancer genetic predisposition plays an important role in the emergence of the disease.

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