Radiation sickness, also known as acute radiation syndrome or ionizing radiation injury, is illness resulting from human exposure to ionizing radiation. The radiation exposure may be from natural sources, such as radium, or from man-made sources, such as x rays, nuclear reactors, or atomic bombs. Ionizing radiation penetrates cells of the body and ultimately causes damage to critically important molecules
|* includes occupation exposure, nuclear fallout, and the production of nuclear materials for nuclear power and weapons|
|Rocks, soil, and groundwater||8%|
|Medical x rays||11%|
such as nucleic acids and enzymes. Immediate cell death may occur if the dose of ionizing radiation is sufficiently high; lower doses result in cell injury which may preclude cell replication. Tissues at greatest risk for radiation injury are those which have cells that are rapidly dividing. Blood forming cells, the lining to the gastrointestinal tract, skin, and hair forming cells are particularly vulnerable. Muscle, brain, liver, and other tissues, which have a low rate of cell division, are less so.
Epidemiological data on radiation sickness has been accumulated from the study of individual cases, as well as from the study of large numbers of afflicted individuals, such as the survivors of the atomic bombing of Hiroshima and Nagasaki and the 135,000 people evacuated from close proximity to the fire at the Chernobyl Nuclear Power Station in 1986.
In those who survive, radiation sickness may be characterized by four phases. The initial stage occurs immediately after exposure and is characterized by nausea, vomiting, weakness, and diarrhea. This is a period of short duration, typically one or two days. It is followed by a period of apparent recovery lasting for one to three weeks. No particular symptoms appear during this time. The third stage is characterized by fever, infection, vomiting, lesions in the mouth and pharynx, abscesses, bloody diarrhea, hemorrhages, weight loss, hair loss, bleeding ulcers, and petechiae, small hemorrhagic spots on the skin. During this phase, there is a loss of appetite, nausea, weakness, and weight loss. These symptoms are due to the depletion of cells which would normally be rapidly dividing. Bone marrow depression occurs with reduced numbers of white blood cells, red blood cells, and blood platelets. Gut cells that are normally lost are not replaced and hair follicle cells are depressed resulting in hair loss. If death does not occur during this phase, a slow recovery follows. This is the fourth phase, but recovery is frequently accompanied by long-lasting or permanent disabilities including widespread scar tissue, cataracts, and blindness.
The toxic side effects of many cancer chemotherapeutic agents are similar to acute radiation sickness, because both radiation and chemotherapy primarily affect rapidly dividing cells. Little effective treatment can be administered in the event of casualties occurring in enormous numbers such as in war or a major nuclear power plant disaster. However, in individual cases such as in accidental laboratory or industrial exposure, some may be helped by isolation placement to prevent infection, transfusions for hemorrhage, and bone marrow transplantation.
[Robert G. McKinnell ]
Wald, N. "Radiation Injury." In Cecil Textbook of Medicine, edited by P. B. Beeson, et al. 15th ed. Philadelphia: Saunders, 1979.
radiation sickness, harmful effect produced on body tissues by exposure to radioactive substances. The biological action of radiation is not fully understood, but it is believed that a disturbance in cellular activity results from the chemical changes caused by ionization (see ion). Some body tissues are more sensitive to radiation than others and are more easily affected; the cells in the blood-forming tissues (bone marrow, spleen, and lymph nodes) are extremely sensitive. Radiation sickness may occur from exposure to a single massive emanation such as a nuclear explosion (such as Hiroshima and Nagasaki), or it may occur after repeated large exposure or to even very small doses in a plant or laboratory, since radiation effects are cumulative. Moreover, exposure to the ultraviolet radiation of the sun can cause tissue destruction and trigger mutations that can lead to skin cancer. Radiation sickness may be fairly mild and transitory, consisting of weakness, loss of appetite, vomiting, and diarrhea. Since even in a mild dose of radiation the blood-forming tissue is destroyed to some extent, there is a reduction in the supply of blood cells and platelets. This increases the tendency to bleed and reduces the body's defense against infection. After a massive dose of radiation the reaction may be so severe that death quickly ensues. This is usually due to severe anemia or hemorrhage, to infection, or to dehydration. Extremely high doses damage the tissues of the brain, and death usually follows within 48 hr, as was demonstrated at Chernobyl. There is no treatment for radiation sickness, although it is sometimes possible for persons to survive otherwise lethal doses of radiation if bone marrow transplants are performed. Potassium iodide is to protect against thyroid cancer from radiation exposure, but the drug should ideally be taken four hours prior to the exposure. Exposure to radiation can cause genetic mutation; the progeny of those subjected to excessive radiation tend to show deleterious genetic changes. The genetic damage from the atomic bombs dropped on Japan is still evident and such damage will continue to surface in people directly affected by the nuclear diasaster at Chernobyl. Persons working with radioactive materials or X rays protect themselves from excessive exposure to radiation by shields and special clothing usually containing lead. Processes involving radioactive substances are observed through thick plates of specially prepared glass that exclude the harmful rays. A dosimeter, a device measuring the amount of radiation to which an individual has been exposed, is always worn by persons working in radioactive areas.