Research project RISC-RAD’s annual meeting contributes to change the way we see ionizing radiations.

Throughout our life, we are exposed daily to ionizing radiation (IR) emitted by Earth, during routine medical diagnosis exams, or in the workplace for professionals such as nuclear workers but also cabin crew members of airline companies. How aware is the public of being exposed to low doses of IR? Accounting for about 2,4 mSv/year/person, these unperceived exposures to IR are considered harmless by radiation protection standards based on biological effects the current state of science allows to detect…

But how to be sure that what you can not see does not exist? Part of the answer is expected to come from European research project RISC-RAD (Radiosensitivity of Individuals and Susceptibility to Cancer induced by Ionizing Radiations), which just held its midterm meeting in Leiden, The Netherlands, from 4 to 6 May 2006. This four-year project funded by the European Commission (EC) started on 1st January 2004 and addresses the challenging issue of cancer risk assessment at low doses of IR.

“Under the dose of 100 mSv, epidemiological studies failed to demonstrate long term effects on organisms of exposure to ionizing radiations, because, if they exist, these effects are masked by the high cancer incidence of 25 % in the population”, explains Laure Sabatier, coordinator of RISC-RAD and head of the Radiobiology and Oncology Lab in the French Atomic Energy Commission. “This is why a biological approach is needed, starting with improving our understanding of the mechanisms by which ionizing radiation induce cancer”. Ionizing radiation act as a stress on cells, provoking immediate lesions on DNA double-helix, including strand breaks associated with base modifications. Since Hiroshima and Nagasaki bombings, long term effects of exposure to IR are known to be cancers.

“The mechanisms by which immediate effects of IR lead to long term effects some twenty years later remain unclear” says Dr. Sabatier. Gathering 80 scientists in 29 research institutes from 11 countries, the second RISC-RAD annual meeting in Leiden allowed partners to measure the knowledge gained. In 2005, 72 publications in international scientific journals were achieved through RISC-RAD funding. Some major findings concerned role of Artemis protein in the repair of clustered DNA lesions, consequences of loss to a single telomere in genomic instability, identification of new genes influencing susceptibility to tumorigenesis, and improvement of mathematical models for biological responses to IR. The unique scope of areas covered by these publications was made possible by integrating European research efforts in low dose research into a single project, whose cost is estimated at 30 million euros. RISC-RAD comes under EC 6th Framework Programme for research within EURATOM treaty, which promotes a safe use of nuclear power, including the protection of man and the environment.

The results obtained so far within RISC-RAD show a growing body of evidence that genetic variations could induce differences of response to exposure to IR between individuals. In other words, the same low dose of IR could do no harm at all to some people, and induce a cancer on others, depending on their genetic background. Identification of new genes involved in radiosensitivity is part of RISC-RAD. A critical issue for radiation protection is to be able to assess individual risk taking in account genetic parameters, and not only the average risk as estimated by epidemiological studies.

“The strong point of RISC-RAD is that experimentalists and modelers are working hand in hand to infuse new biological findings into predictive mathematical models” explains Dr. Sabatier. “Thanks to RISC-RAD, the way we see ionizing radiation is changing. Far from being a blessing when it comes to radiotherapy or a plague when it comes to nuclear power, IR are anyway part of our natural environment at low doses. Understanding the mechanisms through which they jeopardize human health will enable to adapt radioprotection standards to individual cases and to promote a safer use of radiations”.