The radioactive gas radon is the most important natural source of human exposure to ionising radiation. In most countries the majority of the exposure is received indoors, especially in houses and other dwellings.

Radon is known to be a human carcinogen and studies of underground miners exposed occupationally, and usually at very high concentrations, have consistently demonstrated an increased risk of lung cancer.

Case-control studies of lung cancer have now been carried out in a number of different countries.  In these studies radon concentrations have been measured in both current and former homes of the study subjects and detailed smoking histories have also been collected. None of these studies is large enough on its own to assess the risks with sufficient precision to provide useful estimates, or to assess satisfactorily the way in which radon and the smoking can act together to cause lung cancer.  Greater statistical precision can, however,  be achieved by combining information from several studies. This cannot be done satisfactorily from published information, and it is necessary to collate the data at the individual level.

Information from all the studies carried out in Europe have previously been analysed (see link, right), and similar analyses have been carried out of data from the North American and Chinese studies. These analyses confirm that radon causes lung cancer in ordinary homes and have demonstrated that the risk is much greater in current smokers and ex-smokers than in lifelong non-smokers. At present, data on individual subjects from all 25 major studies that have been carried out worldwide is being collated and analysed.

The results of this collaborative analysis will provide more precise estimates of the lung cancer risk that can be attributed to residential radon exposure, which will help in formulating appropriate public health strategies.

 


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