discusses the relationship between radiation dose and the different health effects
that may result.
Radiation doses of different sizes, delivered at different rates to different parts of the body, can cause different types of health effect at different times.
A very high dose to the whole body can cause death within weeks. For example, an absorbed dose of 5 gray or more received instantaneously would probably be lethal, unless treatment were given, because of damage to the bone marrow and the gastrointestinal tract.
medical treatment may save the life of a person exposed to
5 gray, but a whole body dose of, say, 20 gray would almost certainly be fatal even with medical attention.
A very high dose to a limited area of the body might not prove fatal, but other early effects could occur. For example, an instantaneous absorbed dose of
5 gray to the skin would probably cause erythema — painful reddening of the skin — within a week or so, whereas a similar dose to the reproductive organs might cause sterility.
These types of effect are called deterministic effects: they occur only if the dose or dose rate is greater than some threshold value, and the effect occurs earlier and is more severe as the dose and dose rate increase.