The best prevention for radiation sickness is to minimize the dose suffered by the human, or to reduce the dose rate.
Increasing distance from the radiation source reduces the dose according to the inverse-square law for a point source. Distance can sometimes be effectively increased by means as simple as handling a source with forceps rather than fingers.
The longer that humans are subjected to radiation the larger the dose will be. The advice in the nuclear war manual entitled "Nuclear War Survival Skills" published by Cresson Kearny in the U.S. was that if one needed to leave the shelter then this should be done as rapidly as possible to minimize exposure.In chapter 12 he states that "''Quickly putting or dumping wastes outside is not hazardous once fallout is no longer being deposited. For example, assume the shelter is in an area of heavy fallout and the dose rate outside is 400 R/hr enough to give a potentially fatal dose in about an hour to a person exposed in the open. If a person needs to be exposed for only 10 seconds to dump a bucket, in this 1/360th of an hour he will receive a dose of only about 1 R. Under war conditions, an additional 1-R dose is of little concern.''"
In peacetime, radiation workers are taught to work as quickly as possible when performing a task which exposes them to radiation. For instance, the recovery of a lost radiography source should be done as quickly as possible.Reduction of incorporation into the human body
Potassium iodide (KI), administered orally immediately after exposure, may be used to protect the thyroid from ingested radioactive iodine in the event of an accident or attack at a nuclear power plant, or the detonation of a nuclear explosive.
KI would not be effective against a dirty bomb unless the bomb happened to contain radioactive iodine, and even then it would only help to prevent thyroid cancer.Fractionation of dose
Devair Alves Ferreira received a large dose during the Goiânia accident of 7.0 Gy. He lived, while his wife received a dose of 5.7 Gy and died. The most likely explanation is that his dose was fractionated into many smaller doses which were absorbed over a length of time, while his wife stayed in the house more and was subjected to continuous irradiation without a break, giving her body less time to repair some of the damage done by the radiation.
In the same way, some of the people who worked in the basement of the wrecked Chernobyl plant received doses of 10 Gy, but in small fractions, so the acute effects were avoided.
It has been found in radiation biology experiments that if a group of cells is irradiated, then as the dose increases, the number of cells which survive decreases. It has also been found that if a population of cells is irradiated, then set aside for a length of time before being irradiated again, the radiation causes less cell death.
The human body contains many types of cells and a human can be killed by the loss of a single type of cells in a vital organ.
For many short term radiation deaths (3 days to 30 days), the loss of two important types of cells that are constantly being regenerated causes death. The loss of cells forming blood cells (bone marrow) and the cells in the digestive system (microvilli which form part of the wall of the intestines is fatal.
In the graph below, dose/survival curves for a hypothetical group of cells have been drawn, with and without a rest time for the cells to recover. Other than the recovery time partway through the irradiation, the cells would have been treated identically.
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