| MadSci Network: Physics |
"I have heard that radiation poisoning is caused by ionization of the cells. Does this mean the cells become electrically charged? if so how? and why does this cause burns and organ failure?"
First, there are two basic kinds of radiation, ionizing and non- ionizing. Both kinds of radiation are part of the electromagnetic spectrum (for a diagram of this, see www.mcw.edu/gcrc/cop/powerlines- cancer-faq/spectrum2.gif).
Radiation sickness is caused by ionizing radiation such as x- rays and gamma rays. When ionizing radiation hits a molecule it can kick an electron out of it. The ejected electron is charged, so it is an ion and this process called ionization. The free (ejected) electrons are much more reactive than the ions produced by something like a machine that creates negative air ions.
The result of the ejection of the electrons is that chemical bonds are broken. In most molecules, a few broken bonds don't matter. But if the broken bonds are in the chemicals that make up the cell's genetic information, the DNA, then bad things can happen. If there is only a little DNA damage, it will probably be repaired. If there is more DNA damage than the cell can fix, then the cells genetic information will be permanently damaged and the cell will be mutated (or even turned into a cancer cell).
If enough DNA damage is done then the cell will die, particularly if it tries to divide, since it will not be able to duplicate the damaged DNA.
If lots of cells have their DNA damaged enough to kill them, you get radiation sickness.
What type of radiation sickness you get will depend on the radiation dose. At a high radiation dose, the critical cells that are damaged are the rapidly-dividing cells that line the gut. Radiation doses high enough to do this will cause death in 3-10 days from what is called the gastrointestinal (GI) syndrome. Currently there is no proven way to treat the GI syndrome in humans.
If the radiation dose is low enough that enough cells stay alive in the gut, the GI syndrome does not occur; but damage to rapidly-dividing cells in the bone marrow can still cause death in 1-2 months from what is called the hematopoietic (or bone marrow) syndrome. We do have ways to treat the bone marrow syndrome, such as with a bone marrow transplant.
If the radiation dose is low enough that enough cells survive in the bone marrow, a person could still get anaemic or be hypersensitive to infection; but they would probably be okay if treated with standard medicines for these symptoms.
If the radiation is concentrated on one part of the body, then enough cells could die to create a burn, even though neither GI or bone marrow are damaged. For example, is there is a high radiation dose to the skin, but the radiation does not penetrate very deeply, then skin cells will die and create what looks vey much like a thermal (heat) burn.
To put it in simpler terms:
ionizing radiation --> ejected electrons --> broken chemical bonds-
-> damaged DNA --> dead cells --> organ damage --> sick people
John Moulder
Radiation Biologist
Medical College of Wisconsin
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