The Dose And Dose-Rate Efficiency Factor (DDREF): Unneeded, Controversial And Epistemologically Questionable

Abstract

Purpose: The aim of the paper is to review the genesis and evolution of the concept termed dose and dose rate effectiveness factor or DDREF, to expose critiques on the concept and to suggest some curse of action on its use.
 Material and methods: Mainly using the UNSCEAR reporting and ICRP recommendations as the main reference material, the paper describes the evolution (since the 70’s) of the conundrum of inferring radiation risk at low dose and dose-rate. People are usually exposed to radiation at much lower doses and dose rates than those for which quantitative evaluations of incidence of radiation effects are available – a situation that tempted experts to search for a factor relating the epidemiological attribution of effects at high doses and dose-rates with the subjective inference of risk at low doses and dose-rates. The formal introduction and mathematical formulation of the concept by UNSCEAR and ICRP (in the 90’s), is recalled. It is then underlined that the latest UNSCEAR radiation risk estimates did not use a DDREF concept, making it de facto unneeded for purposes of radiation risk attribution. The paper also summarizes the continuous use of the concept for radiation protection purposes and related concerns as well as some current public misunderstandings and apprehension on the DDREF (particularly the aftermath of the Fukushima Dai’ichi NPP accident). It finally discusses epistemological weaknesses of the concept itself.
 Results: It seems that the DDREF has become superseded by scientific developments and its use has turned out to be unneeded for the purposes of radiation risk estimates. The concept also appears to be arguable for radiation protection purposes, visibly controversial and epistemologically questionable
 Conclusions: It is suggested that: (i) the use of the DDREF can be definitely abandoned for radiation risk estimates; (ii) while recognizing that radiation protection has different purposes than radiation risk estimation, the discontinuation of using a DDREF for radiation protection might also be considered; (iii) for radiation exposure situations for which there are available epidemiological information that can be scientifically tested (namely which is confirmable and verifiable and therefore falsifiable), radiation risks should continue to be attributed in terms of frequentistic probabilities; and, (iv) for radiation exposure situations for which direct scientific evidence of effects is unavailable or unfeasible to obtain, radiation risks may need to be inferred on the basis of indirect evidence, scientific reasoning and professional judgment aimed at estimating their plausibility in terms of subjective probabilities.