The historical foundations of cancer risk assessment and its adoption by the US EPA in the mid 1970s were based on the discovery of X-ray-induced gene mutations by Hermann J. Muller, its transformation into the linear nonthreshold (LNT) single-hit theory and the recommendations of the model by the US National Academy of Sciences, Biological Effects of Atomic/Ionizing Radiation, Genetics Panels in 1956 and 1972. This testimony summarizes substantial recent revelations which profoundly challenge the use of LNT as a default in cancer risk assessment, showing multiple significant scientific errors and incorrect interpretations, mixed with deliberate misrepresentation of the scientific record by leading ideologically motivated radiation geneticists. These novel historical and scientific findings demonstrate that the scientific foundations of the LNT single-hit model were seriously flawed and should not have been adopted for cancer risk assessment. The testimony supports the recommendation by the EPA to move away from the use of the LNT as a default in cancer risk assessment and to the formal consideration of alternative dose response models such as the threshold, hormetic and other non-linear modeling approaches.
Keywords: Cancer; Dose response; EPA; Hormesis; LNT; Risk assessment.