All information on potential genetic effects in humans is based on animal
data. This requires large populations of animals exposed to much
higher radiation levels than occupational workers will ever receive in the
course of normal work.
Studies of humans exposed at low levels (US Navy nuclear submarine sailors,
nuclear shipyard workers) are ongoing and show no increase in natural incidence of genetic
Due to the lack of direct human evidence to estimate
risk, animal studies are therefore used.
Extrapolation from mice data indicates that at least 1 Gray (100 rad) acute exposure
is required to double the mutation rate in man.