Mutations Induced by Alpha-Particle Radiation—No Evidence for a Bystander Effect

In their article entitled “Unexpected Sensitivity to the Induction of Mutations by Very Low Doses of Alpha-Particle Radiation: Evidence for a Bystander Effect”, Nagasawa and Little (1) present important data on the induction of HPRT mutations in CHO cells at doses down to 0.83 cGy. They interpret their data as indicating an enhanced efficiency for the induction of mutations at doses less than about 3 cGy and ascribe this enhanced efficiency to a “bystander effect” in which mutations are considered to be induced in cells which have not been traversed by an α particle but are affected by neighboring cells which have been traversed by an α particle. They conclude that “Whatever the mechanism, the increased sensitivity to the induction of mutations by very low fluences of alpha particles…could be significant in terms of the estimation of the potential carcinogenic risk in human populations.”...