Radiation paradigm and its shift.

By adopting the concept of scientific paradigm after L. Sagan, the history of paradigm shift in 1950 in radiation protection standard by ICRP from a threshold to a non-threshold model was critically reviewed. The motives for the shift were found later to be scientifically inappropriate. But the present paradigm of a linear, non-threshold model introduced at the 1950s' shift has been accepted in general for main radiation risk, i.e., for carcinogenesis, though there have been many controversies on risk at low dose effects. We can find some motives for another shift among these controversies now. It is the purpose of the present review to stimulate the discussion on a possible new paradigm.