Risk of lung cancer and indoor radon exposure in France.
H. Baysson, M. Tirmarche, G. Tymen, F. Ducloy, D. Laurier, IRPA 2004, 23-28 may, Madrid (Spain).
It is well established that radon exposure increases risk of lung cancer among underground miners. To estimate the lung cancer risk linked to indoor radon exposure, a hospital based case-control study was carried out in France, with a focus on precise reconstruction of past indoor radon exposure over the 30 years preceding the lung cancer diagnosis. The investigation took place from 1992 to 1998 in four regions of France: Auvergne, Brittany, Languedoc and Limousin. During face-to-face interviews, a standardized questionnaire was used to ascertain demographic characteristics, information on active and passive smoking, occupational exposure, medical history as well as extensive details on residential history. Radon concentrations were measured in the dwellings where subjects had lived at least one year during the 5-30 year period before interview. Measurements of radon concentrations were performed during a 6-month period, using two Kodalpha LR 115 detectors, one in the living room and one in the bedroom. The time-weighted average (TWA) radon concentration for a subject during the 5-30 year period before interview was based on radon concentrations over all addresses occupied by the subject weighted by the number of years spent at each address. For the time intervals without available measurements, we imputed the region-specific arithmetic average of radon concentrations for measured addresses of control subjects. Lung cancer risk was examined in relation to indoor radon exposure after adjustment for age, sex, region, cigarette smoking and occupational exposure. The estimated relative risk per 100 Bq/m3 was 1.04, at the borderline of statistical significance (95 percent Confidence Interval: 0.99, 1.11). These results are in agreement with results from other indoor radon case-control studies and with extrapolations from underground miners studies.