Radiation effects on humans

Radiation Effects on Humans
Radiation occurs when unstable nuclei of atoms decay and release particles. There are many different types of radiation. When these particles touch various organic material such as tissue, damage may, and probably will, be done. Radiation can cause burns, cancers, and death.

Units of Measurement
The unit used to measure radiation dosage is the rem, which stands for roentgen equivalent in man. It represents the amount of radiation needed to produce a particular amount of damage to living tissue. The total dose of rems determines how much harm a person suffers. At Hiroshima and Nagasaki, people received a dose of rems at the instant of the explosions, then more from the surroundings and, in limited areas, from fallout. Fallout is composed of radioactive particles that are carried into the upper atmosphere by a nuclear explosion and that eventually fall back to the earth's surface.
Effects of Radiation Exposure on Human Health
Although a dose of just 25 rems causes some detectable changes in blood, doses to near 100 rems usually have no immediate harmful effects. Doses above 100 rems cause the first signs of radiation sickness including: nausea vomiting headache some loss of white blood cells
Doses of 300 rems or more cause temporary hair loss, but also more significant internal harm, including damage to nerve cells and the cells that line the digestive tract. Severe loss of white blood cells, which are the body's main defense against infection, makes radiation victims highly vulnerable to disease. Radiation also reduces production of blood platelets, which aid blood clotting, so victims of radiation sickness are also vulnerable to hemorrhaging. Half of all people exposed to 450 rems die, and doses of 800 rems or more are always fatal. Besides the symptoms mentioned above, these people also suffer from fever and diarrhea. As of yet, there is no effective treatment--so death occurs within two to fourteen days.
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