1) Exposure to chemicals that disrupt the biology of the cells-- these are "carcinogens" and some common examples are cigarette smoke and benzene. Also food preparation, including barbecuing or burning food, increases the carcinogens in food, as well as added preservatives like nitrates. While everyone has some exposure to carcinogens, just by living in a developed society, it is chronic, prolonged exposure that increases the risk most. 2) Exposure to radiation definitely increases cancer risk, and the disease can develop up to 50 years after the exposure! Sources of radiation include "background" radiation from the earth itself, cosmic rays from outer space, and manmade sources like medical X-rays. Obviously getting some radiation is unavoidable, and it is increased when living up in the mountains or flying in a jet plane. In fact, pilots who routinely fly across the Atlantic get enough radiation from cosmic rays to be classified as radiation work- ers! The chance of getting cancer is greater when an unborn or young child gets radiated than an older person. 3) Chronic irritation such as alcohol or cigarette smoke irritating the throat is related to mouth and throat cancer, breathing sawdust to sinus cancer, and chronic drainage tubes in the bladder with cancer there. The irritation seems to encourage the cells to divide abnormally which can start cancer. 4) A person's inherited characteristics may predispose them to getting certain cancers. Examples include people with fair complexions being susceptible to skin cancer from the sun, and rare genetic diseases like family colon polyp syndromes leading to colon cancer and neurofibromatosis (the "elephant man" disease) leading to brain tumors. 5) Certain transmitted diseases may increase cancer risk, especially in genetically susceptible individuals. Common examples include cervical cancer being associated with a sexually transmitted virus, called "human papilloma virus" and certain leukemias associated with "Epstein-Barr virus" (EBV) which normally causes mononucleosis, called "mono" or "the kissing disease". Many can- ers may be a combination of a genetically susceptible person getting what would be just a passing infection in a normal person, but instead they get cancer! 6) A defective immune system can lead to cancer. This defect can arise in several ways. It can be inborn, such as a child born with the rare disease of "immunodeficiency" for which they must be protected from common childhood illnesses. Alternatively, a person may contract a virus like "Human Immunodifficiency Virus" (HIV) which leads to AIDS. These people commonly get a number of rare cancers, such as lymphomas (arising from cells in the immune system) or Kaposi's sarcoma seen as purple bumps on the skin. Another way to get a defective immune system is by taking drugs that suppress the immune system, as are given when organs (like kidneys) are transplanted so they won't be rejected. These patients get lymphomas 100 times more frequently than "normal" individuals. A fascinating theory about cancer is that we are all getting cancerous cells all the time but the normal immune system spots them and kills them before they can divide. In people with an impaired immune system, however, these cells can grow into tumors and then spread. This is the "immunosurveillance" theory of cancer and explains why many alternative treatments work to boost the body's immune system. Interestingly, depressed people have lowered immunity and develop cancer more frequently than happy people! You can see that developing cancer is a combination of some disturbance in the cell, either from within or outside of it, that causes it to start dividing out of control, grow, and spread. While the immune system usually kills abnormal cells, a low immune system can llow cancer cells to escape detection, and make the patient sick. copyright©CancerAnswers, 1994 all rights reserved last updated May 26, 2010