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A precursor of Pasteur”. Medical History.

The three commonly encountered carcinogens are: 1. Chemical carcinogens – Many chemical agents are capable of causing Neoplasms in either humans or animals. Chemical carcinogens are grouped as:- a. Polycyclic aromatic hydrocarbons:-  They are common carcinogens; present in tobacco smoke or automobile exhaust, .Usually cause cancer of lips, oral-cavity, lungs, neck, pancreases, b. Aromatic amines  Commonly found in insecticides, certain foods and Naphthalene. Pathophysiology 19 Usually related with cancer of the bladder. c. Alkylating agents  They can cause cancer when given in large dose. Are usually used as therapeutic agents. example:- Nitrogen mustard – Mustard gas d. Others  Like aflatoxines, nitrosamides, drugs, etc. 2. Physical carcinogenic agents Ionizing radiation is a recognized cause of cellular mutations. Damage to DNA may be direct or indirect. A long latent period often exists between exposure and development of clinical disease. – Example:-leukemia and skin cancers became very common long years later in Hiroshima and Nagasaki,Japan;after atomic bomb detonation. 3. Viral carcinogens (oncogenic viruses) Viruses are thought to cause some human and Animals malignant neoplasms. Current evidence shows that viruses alter the genome of the Pathophysiology 20 infected cells, which then alter the offspring of the host cells. Some of the oncognic viruses are:- 1. EBV (Epstein-Barr virus) associated with Burkett’s lymphoma. 2. HPV (Human-papilloma-virus) associated with cervical cancer and skin-papilloma