High-Level Group on Low-Dose Research (HLG-LDR)
Photo: National Cancer Institute via Unsplash

Analyses of epidemiological data, in particular from atomic bomb survivors in Hiroshima and Nagasaki, are the fundamental basis of the radiological protection system. They support the assumption made for radiological protection purposes that, for low-dose and low-dose-rate exposures (i.e. below 100 mSv or below 0.1 mSv/minute), stochastic effects (e.g. cancer risk) follow a dose response with no threshold. However, the adoption of this Linear Non-Threshold – LNT extrapolation model remains still controversial due to uncertainties in the area of low dose/low dose rate health risks. Current knowledge in radiobiology at low doses or low dose rates also shows that mechanisms involved in carcinogenesis are much more complex than considered a few decades ago. These uncertainties are greater the lower the dose or dose rate. Uncertainties also apply for some non-cancer effects, where epidemiological findings and animal studies might evidence that late tissue reactions (e.g. circulatory diseases, cognitive effects, lens opacities) have dose thresholds that may be lower than previously considered. Focus should be on reducing uncertainties in the range of dose where control is currently exercised, e.g. doses in the range of typical reference levels, dose limits and constraints.

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These scientific uncertainties and underlying assumptions have determined the way in which the optimisation of protection has been implemented in various prevailing circumstances for many years, very often being interpreted as minimisation of radiological exposure.

Reducing this uncertainty would certainly improve the robustness of the radiological protection system and should help to better structure and size radiological protection decisions. Similarly, it could ease ionising radiation risk communication to the public.

For this reason, great importance has been given to such research by public funding organisations (e.g. specialised government agencies, the European Commission, and national research foundations). In view of these vast research efforts, and given the aspiration for effective cooperation and coordination on the regional and national level, the NEA is in a unique position to successfully channel the research efforts that are being undertaken worldwide.

In 2019, the NEA Committee on Radiological Protection and Public Health (CRPPH) recommended at its 77th annual meeting the establishment of the High-Level Group on Low-Dose Research (HLG-LDR) with the objective to analyse the situation and to propose a way forward to improve the effectiveness and efficiency of research through global networking to coordinate ongoing and future low-dose research projects. An initial group of voluntary research funding and implementing organisations developed a roadmap and oriented preliminary approaches. This work was endorsed by the CRPPH at its 78th meeting in 2020, clearing the way for the establishment of the HLG-LDR as an official CRPPH working group.

The overall objective of the High-level Group on Low Dose Research (HLG-LDR) is to support radiological protection policy, regulation and implementation choices by improving the effectiveness and efficiency of research through global networking for the co-ordination of ongoing and future low-dose research projects. The HLG-LDR will facilitate the communication of research project objectives and results to stakeholders.

The specific objective of the HLG-LDR is to build a global network that facilitates collaboration among ongoing and planned low-dose / low dose rate ionising radiation research programmes and encourages the collective sharing of information and resources.

To achieve this, the HLG-LDR has the mandate to:

  • develop approaches and tools to share information on ongoing and planned research worldwide and to better structure the existing knowledge on radiation-induced effects on humans and non-human species;
  • use these approaches/tools to identify research gaps in the field of low dose/low dose rate effects, and develop mechanisms for prioritisation and co-ordination worldwide;
  • share experience such that research planning, implementation and result reporting can be efficiently and effectively communicated to decision makers and other relevant stakeholders.


Examples of concrete tasks by the HLG-LDR include pioneering work on the creation of a Low Dose Research database, investigating a possible adaptation of the OECD’s Adverse Outcome Pathway (AOP) in the area of low-dose and low-dose rates, and developing a policy-orientated and promotional communication strategy.