Linear No-Threshold Model vs. Radiation Hormesis

Abstract

ᮀ The atomic bomb survivor cancer mortality data have been used in the past to justify the use of the linear no-threshold (LNT) model for estimating the carcinogenic effects of low dose radiation. An analysis of the recently updated atomic bomb survivor cancer mortality dose-response data shows that the data no longer support the LNT model but are consistent with a radiation hormesis model when a correction is applied for a likely bias in the baseline cancer mortality rate. If the validity of the phenomenon of radiation hormesis is confirmed in prospective human pilot studies, and is applied to the wider population, it could result in a considerable reduction in cancers. The idea of using radiation hormesis to prevent cancers was proposed more than three decades ago, but was never investigated in humans to determine its validity because of the dominance of the LNT model and the consequent carcinogenic concerns regarding low dose radiation. Since cancer continues to be a major health problem and the age-adjusted cancer mortality rates have declined by only ~10% in the past 45 years, it may be prudent to investigate radiation hormesis as an alternative approach to reduce cancers. Prompt action is urged.

Low Dose Radiation Adaptive Protection to Control Neurodegenerative Diseases

“…This curvature arises due to the less than expected cancer rates for the dose range of 0.3-0.7 Gy (See text on p.238 of the publication (Ozasa et al, 2012)). It results in a non-linearity of dose response that cannot be explained using the LNT model but is consistent with the radiation hormesis model (Doss, 2013).…”

“…An analysis of the reported cancer incidence among the residents of apartments in Taiwan who were subjected to LDR from contaminated building materials (Hwang et al, 2006;Hwang et al, 2008) has shown a reduced overall cancer incidence in the radiated cohort in comparison to an age-matched control group (Doss, 2013).…”

Biological Effectiveness of Ionizing Radiation: Acute vs. Protracted Exposures

“…In the study of Hiroshima and Nagasaki survivors [22], it was concluded that zero dose is the best estimate for the dose threshold, thus validating the LNT. This conclusion is, however, regarded questionable as the analysis had a priori restricted the possible functional forms of the dose-response relationship, resulting in the conclusion on a zero dose threshold [5,26]. If a more generalized functional form was used, the conclusion would have been different, as the lower bounds of the 95% confidence intervals would have been below zero for low doses; more details are in [5].…”

“…This conclusion is, however, regarded questionable as the analysis had a priori restricted the possible functional forms of the dose-response relationship, resulting in the conclusion on a zero dose threshold [5,26]. If a more generalized functional form was used, the conclusion would have been different, as the lower bounds of the 95% confidence intervals would have been below zero for low doses; more details are in [5]. The artificial neural networks method was reported to have circumvented the limitation of [22] and demonstrated the presence of a threshold of excess relative risk in humans exposed to ionizing radiation [27].…”

“…The topics of the threshold, hormesis and DDREF are interrelated with the linear no-threshold theory (LNT). Hormesis and LNT are considered controversial by many scientists; discussion is in [3][4][5][6][7][8]. The LNT is corroborated by the following arguments: the more tracks go through a cell nucleus, the more DNA damage would result and the higher the risk of malignant transformation would be.…”