An initiative to bring together all the scientific research on exposure to low and very low doses of ionising radiation will improve the global radiological protection system and could have major implications for dealing with the rehabilitation of areas affected by the March 2011 Fukushima-Daiichi nuclear accident, the head of the initiative has said.
Jacques Repussard, director-general of the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and president of Melodi (Multidisciplinary European Low Dose Initiative), told NucNet that science has not yet provided all the answers that governments need to respond to concerns about low doses of radiation.
Epidemiological studies, backed by animal experiments, have established that exposure to radiation levels above 100 millisieverts increases the risk of cancer in a predictable, dose-dependent way. But the risks to health at lower exposure levels – the sort of levels in evidence in Fukushima prefecture after the accident – have proven harder to pin down and evaluate.
One of the aims of Melodi is to establish an international consensus on the actual exposure of the thousands of workers involved in accident management at Fukushima in the immediate aftermath of the accident. Another aim is to evaluate the environmental exposure risks resulting from contamination in Fukushima prefecture and beyond.
Mr Repussard said IRSN directly contributes to attaining the first of these aims. One of its senior experts has been leading the working group of Unscear (United Nations Scientific Committee of the Effects of Atomic Radiation) responsible for part of the UN report dealing with worker exposure during the Fukushima accident.
This report is due to be published soon and will present the international evaluation of exposure data provided by Tepco, the operator of Fukushima- Daiichi, and other Japanese institutions for around 30,000 workers.
For the second aim, IRSN experts and researchers are working with their Japanese colleagues – particularly at Fukushima University – on the evaluation of radiological consequences for the environment and population.
IRSN researchers also contribute to programmes aimed at a better understanding of the impact of radioactive contaminants on wildlife and ecosystems. Mr Repussard said the knowledge gained from this work is “a key to the success” of many local programmes aimed at the rehabilitation of agriculture – for example rice production – and more generally for ensuring the continuity of economic and social activity in the area.
Mr Repussard said it is important to address the issue of low-dose effects of radiation using a “mechanistic approach”, as opposed to the epidemiological approach. Questions need to be answered such as: What happens inside the cell when a particle or photon of ionising radiation hits it? What happens next, and what impact does the event have on the cell? How does the cell react and communicate with other cells when releasing stress-defence actions?
On the most practical level, it is known that some people have higher secondary effects than others after the same radiotherapy treatment. Yet the reasons for the differences in response are not understood. Around a quarter of radiotherapies lead to secondary effects, which are sometimes severe and impairing.
“These secondary effects could be limited if we better understood the phenomena which affect the healthy tissue surrounding an irradiated tumour. This tissue inevitably receives a small part of the radiation during therapy,” Mr Repussard said.
“We could then better protect the patient by adjusting the dose to the individual sensitivity. It is unsatisfactory that in the 21st century, 50 years after radiotherapy was invented, we still do not understand these things.”
On Fukushima, Mr Repussard said understanding and managing the low-dose radiological risk is vital for the socio-economic future of the area around the nuclear station. Risk understanding and management contribute to restoration of trust in society. This trust can only result from transparency on the side of the nuclear operator and the public authorities.
Jacques Repussard was appointed director general of IRSN in 2003. He is also chairman of the Committee on the Safety of Nuclear Installations (CSNI) of the OECD Nuclear Energy Agency and president of the European Technical Support Organisations Network (Etson).
Melodi is a non-profit association, incorporated under French law. It brings together European universities and research institutes such as IRSN in France and the Belgian Nuclear Research Centre (SCK•CEN), as well as agencies for radiation protection such as the Federal Office for Radiation Protection (BfS) in Germany. The idea is to group all the scientific research dealing with exposure to low doses of ionising radiation, to have a common strategy and then to share the work. In 2009, with the support from the European Commission, a high-level and expert group published a report on research and development issues associated with low-dose exposure problems in Europe. As a consequence, national organisations in Europe signed letters of intent for the establishment of Melodi, which led to the founding of the organisation on 19 October 2010 in Paris.