Case-Control study on Lung Cancer and Indoor Radon in France.
Baysson H , Tirmarche M , Tymen G , Ducloy F , Laurier D , IRPA 11, 23-28/05/2004, Madrid (Spain)..
Background: Radon exposure can induce lung cancer in both underground miners and experimentally exposed animals. 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.
Methods: 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.
Results: A total of 486 cases and 984 controls with at least one dwelling measured were included in the study. After imputation for missing values, the arithmetic mean of the TWA radon concentration experienced by cases during the previous 5-30 years was 146 Bq/m3, while the value for controls was 140 Bq/m3. The relative risks of lung cancer (with 95% confidence intervals in parentheses) in relation to categories of TWA radon concentrations delimited by cutpoints 50, 100, 200 and 400 were: 0.85 (0.59, 1.22), 1.19 (0.81, 1.77), 1.04 (0.64, 1.67), 1.11 (0.59, 2.09) respectively, with TWA radon concentrations below 50 Bq/m3 used as reference category and with adjustment for age, sex, region, smoking status and occupational exposure. The relative risk of lung cancer increased by 0.04 (-0.01, 0.11) per 100 Bq/m3 increase in the TWA radon concentration. When the analysis was limited to the 257 cases and 593 controls for whom all dwellings were measured, the corresponding increase was somewhat higher at 0.07 per 100 Bq/m3 (0.00, 0.14).
Conclusions: Our results provide additional evidence that indoor radon has to be considered as a lung carcinogen, as it is observed both in cohort studies of underground miners and in a large number of indoor radon case-control studies, even if the estimated risk linked to indoor radon exposure is relatively low in comparison to the risk associated with cigarette smoking.