RERF Report No. 2-15

Paper published in Radiation Research§“Comments on Estimating Risks of Low Radiation Doses – A Critical Review ofthe BEIR VII Report and Its Use of the Linear No-Threshold (LNT) Hypothesis by
Edward J. Calabrese and Michael K. O’Connor”
Kevin D. Crowley, Harry M. Cullings, Reid D. Landes, Roy E. Shore and Robert L. Ullrich
Radiat Res 2015 (April); 183 (4) 476-81 (doi: 10.1667/RR4029.1)

Explanation
Recently a Commentary by Calabrese and O’Connor was published in the journal
Radiation Research, criticizing the use of the linear, non-threshold (LNT) model ofionizing-radiation dose-response in a major publication of the U.S. National Academies ofScience (NAS). RERF scientists joined a staff member from NAS in responding to thiscommentary, which contained a number of factual inaccuracies and misleading assertions.
For many years there has been controversy in the worldwide radiation protection
community about the model to be used in relating the excess risk of cancer or otherradiation-related adverse health outcomes to the radiation dose received by an exposed person.
A model often used by standards-setting and advisory bodies is the LNT model, which is basedon the idea that the excess risk is proportional to the dose, at all dose levels. The NAS
Committee on the Biological Effects of Ionizing Radiation (BEIR), in its BEIR VII Phase 2
Report issued in 2006, defended and relied upon the LNT model. This model is often criticizedby those who contend that there is a threshold dose beneath which there is no excess risk, or thatlow doses of radiation actually reduce the risk below the level at zero dose, by stimulating theexposed person’s body in some beneficial way (hormesis).
RERF does not take any official position on the LNT model, and RERF scientists use
both the LNT and other models in their publications. Because RERF scientists were conversant
with many of the issues involved and serve as advisors to NAS committees and other advisory
bodies related to the health effects of ionizing radiation, they could help in responding tocriticisms leveled by (C&O) against the NAS committee’s use of LNT. The authors of the letter
addressed a long list of concerns about the C&O Commentary, including 1) inaccurateassertions about the historical origins of the LNT model in NAS work, 2) a suggestion that theNAS BEIR VII Committee relied on tradition instead of conducting a new and thoroughanalysis, 3) assertions (inconsistent with the preceding ideas) that because the recommendationsof NAS committees have changed somewhat over the decades, they are therefore somehow
unreliable, 4) reliance on selected data to support criticism of the LNT model, 5) reliance on thevisual appearance of plots to make statements that should be based on statistical model-fitting,1RERF Report No. 2-15parameter estimation, and hypothesis testing, and 6) an assertion that that the use of a dose- anddose-rate effectiveness factor (DDREF) in the BEIR VII risk model somehow invalidates theLNT model in the low-dose range. These are just a few of the points in the NAS/RERF response
to C&O’s Commentary, both of which the reader is encouraged to consult for more detail.
The Radiation Effects Research Foundation has studied A-bomb survivors and their offspring in
Hiroshima and Nagasaki for more than 60 years. RERF’s research achievements are considered theprincipal scientific basis for radiation risk assessment by the United Nations Scientific Committee on theEffects of Atomic Radiation (UNSCEAR) and for recommendations regarding radiation protection
standards by the International Commission on Radiological Protection (ICRP). RERF expresses its
profound gratitude to the A-bomb survivors and survivors’ offspring for their cooperation in our studies.

§Radiation Research, which is an official monthly journal of the Radiation Research Society, publishes

original, peer-reviewed papers and review articles on radiation effects and related issues in the fields ofphysics, chemistry, biology, and medicine. (Impact factor in 2014: 2.911)2