The Effects of Low Doses of Radiation

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Introduction

It is known that high doses of radiation over a short period of time lead to deterministic effects that can be tied to the radiation dose with great confidence.

For stochastic effects and at low doses it is much harder to prove a relationship. At relatively high doses to quite large groups you may find an increase in the occurrence of quite rare cancers which gives you confidence that you have found a link. For the incidence of more common cancers after exposure to low levels of radiation it is very hard to prove that the cancer was caused by the radiation.

If the baseline frequency of occurrence of a particular type of stochastic effect in a population were low and the radio sensitivity for a health effect of that type were high (as is the case with some thyroid cancers following exposure in childhood), causation of a health effect in a particular individual by radiation exposure could be plausible, particularly if that exposure were high. But even then, the stochastic effect in an individual could not be unequivocally attributed to radiation exposure, owing to other possible causes.

At acute doses above 1 Gy, deterministic effects that are clinically observable in individuals can be attributed to radiation with increasing confidence as the dose increases. Stochastic effects (e.g. cancer) in an individual cannot be unequivocally attributed to radiation exposure, however collectively an observed increase in the incidence of such health effects in a population can in some situations be attributable to radiation exposure when the dose is moderate or high. For low doses, risks are biologically plausible, though they are not currently verifiable through testing.

Reference Sources, Effects and Risks of Ionizing Radiation UNSCEAR 2012 Report (Page 68)