Risque de cancer du poumon après exposition au radon : état des connaissances épidémiologiques

Purpose of the study. Radon is a radioactive gas of natural origin; it is produced by the disintegration of uranium and radium located in the earth's crust. Radon is present in the outdoor air and concentrates in houses and other buildings, with highest radon concentrations in dwellings built on granitic subsoils. Radon is known to be a human lung carcinogen. Studies of underground miners exposed occupationally have consistently demonstrated an increased risk of lung cancer. Similar observations have been made in animal studies. Method. However, there is little direct information on the risk of lung cancer that is associated with exposure to residential radon, for which concentrations are usually much lower than those of miners and the conditions of exposure are different. For this purpose, residential case: control studies have been carried out in Europe, United States and China. But lack of statistical power prevented most of them from showing a significant risk. To deal with this problem, several joint analyses have been conducted in recent years. In joint analyses, individual data on smoking habits, occupational exposure, and on radon exposure history, based on long-term measurements in all the dwellings occupied by the subjects over the 30 past decades, have been assembled in a uniform manner. Results. Assessing the lung cancer risk associated with indoor radon exposure is not easy: the risk is low and uncertainties in assessing exposure may underestimate the risk. Large-scale studies are able to show a significant association between lung cancer risk and indoor radon exposure, to precise the combined effect of smoking history and radon exposure on lung cancer development and to estimate the lung cancer risk due to radon among never-smokers. The best evidence would come from the Word Pooling Study (including all the 24 individual indoor radon studies), which is actually under-way. This international project is supported by the EC under the program Alpharisk, coordinated in France by the Institute for Radiological and Nuclear Safety (IRSN). Conclusion. These joint analyses report a significant lung cancer risk associated with indoor radon exposure, even for low radon concentrations. The relative risk of lung cancer from indoor radon exposure is about the same for both smokers and non-smokers; however because the baseline lung cancer rate for smokers is much higher than for never-smokers, absolute risks of lung cancer from residential radon are much higher for smokers and recent ex-smokers than for never-smokers. These results are crucial to the development of policies to reduce radon exposure in homes in parallel with national programs to reduce cigarette-smoking habits. (c) 2008 Elsevier Masson SAS. All rights reserved.