La controverse sur les effets des faibles doses de rayonnements ionisants et la relation linéaire sans seuil

From December 2004 to July 2005, three reports on the effects of low doses of ionising radiation were released: ICRP (2004), the joint report of the French Academies of Science and Medicine (Tubiana et al 2005), and a report from the American Academy of Sciences (BEIR VII 2005). These reports quote the same recent articles on the biological effects of low doses, yet their conclusions diverge. The French report concludes that recent biological data show that the efficacy of defense mechanisms is modulated by dose and dose rate and that linear no threshold (LNT) is no longer plausible. The ICRP and the BEIR VII reports recognise that there are biologic arguments against LNT but feel that there are not sufficient biological proofs against it to change risk assessment methodology and subsequent regulatory policy based on LNT. They point out the remaining uncertainties and the lack of mechanistic explanations of phenomena such as low dose hyperlethality or the adaptive response. In this context, a critical analysis of the available data is necessary. The epidemiological data and the experimental data challenge the validity of the LNT hypothesis for assessing the carcinogenic effect of low doses, but do not allow its exclusion. Therefore, the main criteria for selecting the most reliable dose-effect relationship from a scientific point of view should be based on biological data. Their analysis should help one to understand the current controversy.

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The debate on the use of linear no threshold for assessing the effects of low doses

et al. 2006

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“…This LNT model concept was introduced into the radiological protection system in the late 1950s (ICRP 1959). Nevertheless, several forms of dose-effect relationship appear possible at low doses, based on biological considerations (UNSCEAR 2012, NASEM 2022, and the use of the LNT model has since been the subject of numerous scientific discussions and controversies (Brenner et al 2003, Wakeford 2005, Tubiana et al 2007, Little et al 2009, Calabrese 2016. Some experts or groups argue that the LNT model could overestimate the actual risk, supporting a possible existence of a dose threshold below which there is no risk, or perhaps even health benefits (hormesis effects).…”

Section: Introductionmentioning

confidence: 99%

The scientific basis for the use of the linear no-threshold (LNT) model at low doses and dose rates in radiological protection

Laurier¹,

Billarand²,

Klokov³

et al. 2023

J. Radiol. Prot.

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The Linear No-Threshold (LNT) model was introduced into the radiological protection system about 60 years ago, but this model and its use in radiation protection are still debated today. This article presents an overview of results on effects of exposure to low linear-energy-transfer (LET) radiation in radiobiology and epidemiology accumulated over the last decade and discusses their impact on the use of the LNT model in the assessment of radiation-related cancer risks at low doses. The knowledge acquired over the past 10 years, both in radiobiology and epidemiology, has reinforced scientific knowledge about cancer risks at low doses. In radiobiology, although certain mechanisms do not support linearity, the early stages of carcinogenesis comprised of mutational events, which are assumed to play a key role in carcinogenesis, show linear responses to doses from as low as 10 mGy. The impact of non-mutational mechanisms on the risk of radiation-related cancer at low doses is currently difficult to assess. In epidemiology, the results show excess cancer risks at dose levels of 100 mGy or less. While some recent results indicate non-linear dose relationships for some cancers, overall, the LNT model does not substantially overestimate the risks at low doses. Recent results, in radiobiology or in epidemiology, suggest that a dose threshold, if any, could not be greater than a few tens of mGy. The scientific knowledge currently available does not contradict the use of the LNT model for the assessment of radiation- related cancer risks within the radiological protection system, and no other dose-risk relationship seems more appropriate for radiological protection purposes.

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“…As an example of the policy-science debate for cancer, consider the differences between the US and the French Academies (i.e., the US National Academies of Science, the French Academy of Sciences, and the French National Academy of Medicine) regarding the effects of ionizing radiations at low doses. Although the US (BEIR VII, Phase 2, 2006) supports the LNT using low-dose linear models fit to epidemiological data, the French Academies doubt its validity, pointing to fundamental biological repair mechanisms that prevent linearity at low doses (Tubiana and Aurego, 2005). Current regulatory defaults neither resolve this ambiguity nor necessarily increase protection.…”

Section: Introductionmentioning

confidence: 99%

Changing the Risk Paradigms can be Good for Our Health: J-Shaped, Linear and Threshold Dose-Response Models

2011

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A. L. Cox, Jr. ᮀ Cox Associatesᮀ Both the linear (at low doses)-no-threshold (LNT) and the threshold models (Sshapes) dose-response lead to no benefit from low exposure. We propose three new models that allow and include, but do not require -unlike LNT and S-shaped models -this strong assumption. We also provide the means to calculate benefits associated with bi-phasic biological behaviors, when they occur and propose:1. Three hormetic (phasic) models: the J-shaped, inverse J-shaped, the min-max, and 2. Method for calculating the direct benefits associated with the J and inverse J-shaped models.The J-shaped and min-max models for mutagens and carcinogenic agents include an experimentally justified repair stage for toxic and carcinogenic damage. We link these to stochastic transition models for cancer and show how abrupt transitions in cancer hazard rates, as functions of exposure concentrations and durations, can emerge naturally in large cell populations even when the rates of cell-level events increase smoothly (e.g., proportionally) with concentration. In this very general family of models, J-shaped doseresponse curves emerge. These results are universal, i.e., independent of specific biological details represented by the stochastic transition networks. Thus, using them suggests a more complete and realistic way to assess risks at low doses or dose-rates.

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La controverse sur les effets des faibles doses de rayonnements ionisants et la relation linéaire sans seuil

Cited by 11 publications

References 134 publications

The debate on the use of linear no threshold for assessing the effects of low doses

The debate on the use of linear no threshold for assessing the effects of low doses

The scientific basis for the use of the linear no-threshold (LNT) model at low doses and dose rates in radiological protection

Changing the Risk Paradigms can be Good for Our Health: J-Shaped, Linear and Threshold Dose-Response Models

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