Blake Tomlinson, King's High School, asks :-

What would happen to a living creature if it was exposed to radiation for a long period of time? Would it mutate and die, mutate and live, its offspring mutate, something else?

John Poletti, a physicist at the National Radiation Laboratory, responded.

Ionizing radiation has three main effects. It can directly damage living tissue, it can cause cancer to develop later and it can cause mutations in the offspring (but not the creature exposed).

Direct effects include radiation burns and cataracts in the eyes. There is a threshold dose below which no direct effect can occur. At very high doses, damage to the digestive system, destruction of the blood forming cells in the bone marrow and damage to the central nervous system can be caused. This can lead to death.

Cancer can be caused by radiation, even at quite low doses, with no threshold dose. The higher the dose, the higher the chance of cancer being caused. There is a latent period between exposure to radiation and the appearance of the cancer, of at least a few years and often twenty years or more. At low doses, such as for chest x-rays, the chance of cancer can be neglected in comparison with the normal risks of everyday life. Even at doses such as those experienced by the Japanese atomic bomb survivors the radiation cancer risk is still very much less than the natural cancer risk.

Hereditary effects are caused by radiation exposure of the reproductive organs of either parent (or both). While hereditary effects have been shown in animal studies, none have yet been observed in humans.

So, what would happen if a creature is exposed to radiation for a long time? At low dose rates, such as the natural background level, probably nothing will happen. There is a very small chance of a cancer being caused or of a mutated offspring. At higher dose rates, the chance of cancer increases as does the chance of hereditary effects, but no direct effects can occur. At higher dose rates still, the dose will accumulate sufficiently to exceed the threshold for direct effects. We would then start to see skin burns or cataracts. At extreme dose rates, cancer would not be a problem, because death would occur due to damage to essential bodily systems, long before cancer could appear!