What would extreme radiation do to the body?

What does radiation do to the human body and why?

• What exactly takes place when one is exposed to high levels of radiation?  How does it affect your body and why does it do what it does?

• Answer:

  There are different kinds of electromagnetic radiation; generally the type is determined by energy (or frequency). There is a well-recognized cut-off between radiation that has enough energy to force an electron from its atom (ionizing radiation, like x-rays) and radiation that doesn't (like light or microwaves). Ionizing radiation (the type created by nuclear reactions) has several different common sub-categories with varying biological effects. Alpha particles. These are big, heavy, and do massive damage to tissue (relatively). Fortunately, they are easily stopped even by the dead outer layer of skin. So if the source it outside of your body, there is really no effect. If it's inside  though (like inhaled radon), it can cause significant cellular damage. (http://en.wikipedia.org/wiki/Alpha_particle) Gamma/X-rays. These are just very high energy light. Most of the time they will go right through a cell without causing any damage. But occasionally they will hit part of a cell and cause damage. (http://en.wikipedia.org/wiki/Gamma_ray) FYI -- The use of the terms gamma and x-ray is inconsistent. Physicists tend to define a gamma ray as anything emitted by a decay in the nucleus of an atom, while an x-ray comes from electron motion/decay. Elsewhere, gamma rays are used to describe very high-energy radiation, while x-rays are used for lower energy. Beta particles. These are free electrons. They can penetrate farther than alpha particles (through the outer layer of skin), but not much. They also cause less damage than an alpha particle. Like alpha particles, these are very dangerous if the source is ingested, but not very dangerous if they are outside of your body.  (http://en.wikipedia.org/wiki/Beta_particle) Neutrons. These are tricky little particles, which tend to easily pass through anything that doesn't have lots of hydrogen in it (with rare exceptions). Unfortunately, water is mostly hydrogen, so these tend to go right through steel and such and then stop right inside your body, causing damage. These are rare though, and are only commonly encountered inside of an operating nuclear reactor. (http://en.wikipedia.org/wiki/Neutron_radiation) Common radiation measurements, such as REM and Sievert (Sv), account for these differing biological effects by multiplying each type of radiation by set factor, based on it's likelihood for damage. These factors are: Alpha, internal: 20 Gamma/x-ray: 1 Beta (electron): 1 Neutron: 1-10 or more, depending on energy Alpha, external: 0 (actually it doesn't have/need a weighting factor since it doesn't impart any energy in living tissue) Until now, I've conveniently avoided what I mean by "cellular damage". When any type of ionizing radiation interacts with a cell it imparts energy into it, which can change the chemical structure of that part of the cell. There are again several possible outcomes. A non-critical part of the cell is damaged. In this case, the cell will recover and function as normal. Note that most of a cell's volume is non-critical, so this is the most common result. A critical part of a cell is damaged, which causes the cell to die. Living organisms have all sorts of complicated error detection and correction features. So, if a critical problem is detected, the cell should just die. This isn't normally a problem, unless you get exposed to an incredibly large amount of radiation and lose lots of cells at once. DNA is damaged, but the cell does not die and continues to reproduce. This could result in cancer if everything goes perfectly wrong. I should note that this is incredibly rare -- each of our bodies is bombarded by thousands of ionizing radiation particles each minute for our entire lives, no matter what. Still, many people never get cancer, and most cases likely aren't from radiation exposure. As far as I know, no study has ever documented long-term harm from radiation exposures that a human is likely to encounter, even in a high risk environment (or what we would call one today, like being a pilot or a uranium mine operator). All current safety standards are based on observing effects from very large doses  (either at once or over time, often from accidents), and assuming that half the dose must cause half the harm, and so on. This is an assumption, and may not be correct (it's likely not). So, the next time someone quotes "twice the safe level of radiation for the general public" you can equate that to "1,000 or more times less radiation than has ever been shown to cause bodily harm". But it's errs on the safe side, which should protect humans from ourselves. With that said, if you're exposed to very large radiation doses in a short period, enough cells in your body will die such that you get acute radiation sickness (http://en.wikipedia.org/wiki/Acute_radiation_syndrome). This is bad, typically including nausea, weakness, and possibly death. However, people have survived even very large radiation doses (enough to cause acute radiation sickness symptoms) and lived long, healthy lives afterwards. Finally, there are other types of ionizing radiation. Some are very common, like neutrinos (you have a million of them in you right now!), but rarely interact with our bodies so their effect is negligible. Others, like high energy protons, are very rare here on earth, but can present problems for spacecraft. Non-ionizing radiation (e.g. radio-waves) is not as well understood, hopefully someone else can shed some light on that...