Cancer risk following low doses of ionising radiation – current epidemiological evidence and implications for radiological protection

International audienceRecent studies suggest that every year worldwide about a million patients might be exposed to doses of the orderof 100 mGy of low-LET radiation, due to recurrent application of radioimaging procedures. This paper presents asynthesis of recent epidemiological evidence on radiation-related cancer risks from low-LET radiation doses ofthis magnitude. Evidence from pooled analyses and meta-analyses also involving epidemiological studies that,individually, do not find statistically significant radiation-related cancer risks is reviewed, and evidence fromadditional and more recent epidemiological studies of radiation exposures indicating excess cancer risks is alsosummarized. Cohorts discussed in the present paper include Japanese atomic bomb survivors, nuclear workers,patients exposed for medical purposes, and populations exposed environmentally to natural background radiationor radioactive contamination. Taken together, the overall evidence summarized here is based on studiesincluding several million individuals, many of them followed-up for more than half a century. In summary,substantial evidence was found from epidemiological studies of exposed groups of humans that ionizing radiationcauses cancer at acute and protracted doses above 100 mGy, and growing evidence for doses below 100 mGy.The significant radiation-related solid cancer risks observed at doses of several 100 mGy of protracted exposures(observed, for example, among nuclear workers) demonstrate that doses accumulated over many years at lowdose rates do cause stochastic health effects. On this basis, it can be concluded that doses of the order of 100 mGyfrom recurrent application of medical imaging procedures involving ionizing radiation are of concern, from theviewpoint of radiological protection