The term applied to the acute effects of ionizing radiation on the whole, or a major part, of the body when the dose is greater than 1 gray (1 Gy) of X-rays or gamma rays, or 1 sievert (1 Sv) of other types of radiation. The effect of radiation depends on the dose and the exposure time. Total-body doses of less than 2 Gy are unlikely to be fatal to a healthy adult. At doses of 1–10 Gy, transient nausea and occasional vomiting may occur, but usually disappear rapidly and are often followed by a 2–3 week period of relative well-being. By the end of this period, the effects of radiation damage to the bone marrow and immune system begin to appear, with repeated infections and petechiae (pinpoint spots of bleeding under the skin). Some people are successfully treated with a bone marrow transplant or by isolation in a sterile environment until the bone marrow recovers. With a dose of 10–30 Gy there is also an early onset of nausea and vomiting, which tends to disappear a few hours later. However, damage to the gastrointestinal tract, which causes severe and frequently bloody diarrhoea (called the gastrointestinal syndrome), and overwhelming infection due to damage to the immune system is likely to result in death 4–14 days after exposure. Acute exposures of more than 30–100 Gy cause the rapid onset of nausea, vomiting, anxiety, and disorientation. Within hours, the victim usually dies due to nervous system damage and oedema of the brain; these effects are called the central nervous system syndrome.
Radiation sickness |
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