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  Radiobiology, in the life sciences, is the study of the interactions between radiation and living systems. The area was opened in 1895 by Wilhelm Röntgen\'s (1845 - 1923) discovery of the x-ray and its diagnostic value in medicine. The use of x-rays spread rapidly and it was soon observed that they had deleterious and occasionally fatal effects upon those regularly exposed to them. Radiobiology grew from these first observations and expanded as it was discovered that other forms of electromagnetic radiation, such as gamma rays and ultraviolet rays, could affect living cells as could particulate radiation such as that emitted by radioisotopes. Such ionizing radiations can cause chemical changes where they interact with atoms and molecules and are thus distinguished from radiations such as visible light and microwaves, which generally cause heating effects. Ionizing radiation delivers energy to atoms with which it interacts causing chemical reactions to occur; in the controlled environment of a living cell this is likely to be destructive, though the effect on the individual depends greatly upon species, insects being capable of surviving far greater doses than mammals.

The effect of ionizing radiation on a cell is to produce random mutations in the DNA. Typically, radiation causes cell death or effects the rate of cell division as a result of damage to DNA, possibly resulting in cancer. A number of early radiation workers, such as Marie Curie, died from cancers caused by the materials they were investigating, and cancers are more common among individuals exposed to high levels of ultraviolet radiation or to nuclear weapons used in warfare or in tests. Cells which are actively dividing (such as cancer cells) are more sensitive to the effects of radiation; this is the basis for the use of radiotherapy in the treatment of cancer, and also explains how sub-lethal doses of radiation can reduce the immunity of an individual by destroying the stem cells which produce white blood corpuscles. Hereditary effects of radiation are confined to instances where the germ cells are exposed and are thus only seen with penetrating radiations such as gamma and x-rays. The mutations produced are almost always harmful and frequently fatal, though the naturally occuring radiation in the environment may be important in the induction of a low-level of mutation which is important in evolution. RB

See also biophysics; teratology.Further reading Eric Hall, Radiation Biology.



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