Radiation sickness is the term for a variety of symptoms that follow a person’s exposure to damaging amounts of certain types of radiation. The radiation may come from nuclear explosions and the resulting fallout, from medical and industrial uses of radioisotopes (radioactive forms of elements), or from such devices as particle accelerators or X-ray machines. Such radiation can ionize (give an electrical charge to) atoms and molecules in body tissues, causing a series of reactions that results in damage to cells. The main symptoms of radiation exposure are loss of appetite, nausea, vomiting, and fatigue. Additional symptoms include hair loss and loss of the body’s ability to fight infection. Exposures to high levels of radiation may cause lasting injury or death.
Some cells are more easily injured by radiation than others. The most sensitive cells are those of the blood-forming bone marrow and of lymphoid tissues. Adult muscle and brain cells are least sensitive to radiation.
Scientists measure radiation exposure in human beings using a unit called the sievert (Sv). The sievert has largely replaced another such unit, the rem. One sievert is equal to 100 rems. A single exposure of 0.70 sievert (70 rems) or less usually produces few or mild symptoms. Higher exposures, of 3 to 4 sieverts (300 to 400 rems), cause illness that is fatal for about 50 percent of the people exposed.
Physicians can treat only the symptoms of radiation sickness. Treatment with antibiotics or blood transfusions helps some people exposed to high doses of radiation survive.
