Several factors are known to produce cancerous growth in tissues. These are collectively called as Carcinogens. Some of the factors/agents of cancer are described below:
1. Physical agents:
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Radiations such as X-rays, UV rays, nuclear disasters can cause cancer in human beings.
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Prolonged exposure to sunlight causes skin cancer.
2. Chemical agents:
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Mainly include hydrocarbons, soot, coal tar, mustard gas, nicotine smoke, phenolic compounds arsenic and heavy metal ions.
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Chewing of tobacco and cigarette smoking causes cancer of lungs, pharynx, pancreas, kidney and oesophagus.
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Cigarette contains carcinogenic agents such as benzopyrene and N-nitrosodimethylamine.
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Alcohol consumption causes liver, oesophagus and rectal cancer.
3. Biological agents:
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Oncogenic viruses are cancer causing viruses.
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Human papilloma virus (HPV) causes cancer of cervix in females.
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HIV also causes a particular type of cancer called Kaposi Sarcoma.
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Epstein Barr virus (EBV) causes nasopharyngeal carcinoma.
4. Dietary factors:
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Consumption of smoked fish causes stomach cancer.
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Consumption of fatty foods causes breast cancer.
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Consumption of beef causes intestinal cancer.
5. Genetic factors:
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Genetic changes resulting from mutation or presence of virus alters the cell, so that it divides uncontrollably.
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Retinoblastoma (eye tumour) occurring in children is an inherited type of cancer.
