This paper summarizes the historical and scientific foundations of the Linear No-Threshold (LNT) cancer
risk assessment model. The story of cancer risk assessment is an extraordinary one as it was based on an
initial incorrect gene mutation interpretation of Muller, the application of this incorrect assumption in
the derivation of the LNT single-hit model, and a series of actions by leading radiation geneticists during
the 1946e1956 period, including a National Academy of Sciences (NAS) Biological Effects of Atomic
Radiation (BEAR) I Genetics Panel (Anonymous, 1956), to sustain the LNT belief via a series of deliberate
obfuscations, deceptions and misrepresentations that provided the basis of modern cancer risk assessment
policy and practices. The reaffirming of the LNT model by a subsequent and highly influential NAS
Biological Effects of Ionizing Radiation (BEIR) I Committee (NAS/NRC, 1972) using mouse data has now
been found to be inappropriate based on the discovery of a significant documented error in the historical
control group that led to incorrect estimations of risk in the low dose zone. Correction of this error by the
original scientists and the application of the adjusted/corrected data back to the BEIR I (NAS/NRC, 1972)
report indicates that the data would have supported a threshold rather than the LNT model. Thus, cancer
risk assessment has a poorly appreciated, complex and seriously flawed history that has undermined
policies and practices of regulatory agencies in the U.S. and worldwide to the present time.