Radiation sickness

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

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.

See also Epidemiology; Nuclear weapons; Nuclear winter; Radiation exposure; Radioactive pollution; Threshold dose

[Robert G. McKinnell ]

RESOURCES

BOOKS

Guskova, A. K., et al. "Acute Effects of Radiation Exposure Following the Chernobyl Accident." In Treatment of Radiation Injuries, edited by D. Browne, et al. New York: Plenum Press, 1990.

Wald, N. "Radiation Injury." In Cecil Textbook of Medicine, edited by P. B. Beeson, et al. 15th ed. Philadelphia: Saunders, 1979.

ra·di·a·tion sick·ness • n. illness caused by exposure of the body to ionizing radiation, characterized by nausea, hair loss, diarrhea, bleeding, and damage to the bone marrow and central nervous system.

radiation sickness Illness resulting from exposure to sources of ionizing radiation, such as X-rays, gamma rays, or nuclear fallout. Diarrhoea, vomiting, fever and haemorrhaging are symptoms. Severity depends upon the degree of radiation, and treatment is effective in mild cases.