Evidence of a Dose Threshold for Radiation-Induced Leukemia

Abstract

In 1958, Neil Wald presented data on the incidence of leukemia among the Hiroshima atomic bomb survivors. These data, which suggested a dose-response threshold for radiation-induced leukemia, were included in the first UNSCEAR report (1958). However, this evidence of a threshold was not recognized. It was obfuscated and concealed. In 2010, Zbigniew Jaworowski identified these data as evidence of radiation hormesis. A letter to the editor in 2014 and 2 articles in 2014 and 2015 presented a graph of these UNSCEAR 1958 data, which revealed a threshold at about 500 mSv. Since the blood-forming stem cells of bone marrow are more radiosensitive than most other cell types, it is reasonable to expect thresholds for inducing other types of cancer by ionizing radiation-their thresholds are likely higher than 500 mSv. A careful examination of the Wald data reveals the suprisingly low incidence of radiogenic leukemia, only 0.5% of the survivors who were in the high radiation zone. Many articles on radiation risk have been published since 2015 by other authors, but none makes reference to this evidence of a threshold, either to challenge or endorse it. In this commentary, the author addresses the comments from a colleague.

Keywords: Hiroshima atomic bomb survivors; cancer; dose–response threshold; hormesis; ionizing radiation; leukemia.

Figure 1.

Number of leukemia cases per year.

Figure 2.

Total number of leukemia cases per million versus radiation dose. Data from UNSCEAR 1958. Evidence of a threshold for radiogenic leukemia is apparent at about 0.7 Sv, or 0.7 Gy assuming RBE = 1.