Exposure to ionising radiation such as X-rays, Gamma rays and particle radiation from radioactive substances forms highly reactive ions in the exposed cells that can rupture the DNA strands, causing mutations in the genes, leading to the development of cancer. It has been observed that the exposures to even low-levels of ionising radiation can cause cancer. In earlier days, the radiologists used to develop thyroid tumours and leukaemias because they were not protected from the X-rays. According to Ernest Sternglass, a professor of radiation physics at the University of Pittsburgh, low-levels of radiation from X rays, background radioactivity and nuclear reactor fallout can cause cancer.
Radioactive waves emitted in the atomic explosions have a significant carcinogenic effect. Most of the survivors of the 1945 atomic bomb explosions at Hiroshima and Nagasaki in Japan developed leukaemia due to exposure to the atomic radiation. After the Chernobyl nuclear accident in 1986, the incidence of thyroid cancer increased 100 times among the children living in the most exposed areas of Ukraine, Belarus and Russia.
Solar radiation (ultraviolet B and ultraviolet C) is the causative factor in about 40 percent of the skin cancers. Ultraviolet radiation induces permanent mutation in the tumour suppressor gene (p53 gene) in the exposed cells that causes skin cancer. Exposure to ultraviolet radiation is increasing, day-by-day, due to the expanding ozone hole in the earth’s upper atmosphere. The people with darker skin are protected from ultraviolet radiation due to the presence of a pigment called Melanin in their skin. Caucasians of Australia are the worst affected from ultraviolet radiation, due to over exposure to sunlight and the least amount of melanin in their skin.
Exposure to electromagnetic radiation, emitted by man-made technological devices and installations can cause cancer. The electromagnetic fields (EMFs) generated by fluorescent lights, electrical wirings, electric motors, food mixers, hair dryers, heaters, electric shavers, vacuum cleaners, microwave ovens, televisions, computers, video terminals and cell phones, etc. emit 30 to 100 times greater EMFs than the permissible limits. Ordinary home appliances generate large cumulative electromagnetic radiation due to proximity of the user to these appliances. The EMFs from these appliances drop off at a distance of about 16 feet but the users usually stand or sit closer to these appliances. It has been observed that prolonged exposure to electromagnetic fields causes mutations in the genes. According to David A. Savitz of the University of North Carolina School of Public Health, children living near the high-tension power lines have twofold higher risk of developing cancer, especially brain tumour & leukaemia. Research done at the Veteran’s Administration Medical Centre in Loma Linda, California has shown that EMFs stimulate the activity of an enzyme called Ornithine decarboxylase that promotes the growth of malignant cells.
Physical irritants such as chronic abrasion of mucus membrane of the gastrointestinal tract by some food item or abrasion of the buccal mucosa by an ill-fitted denture can lead to the development of cancer. The worn out cells in these tissues are to be replaced by the new cells, formed as a result of rapid mitosis (cell division) that increases the chance of mutations in the genes, thus increasing the risk of developing cancer.