Indoor exposure to 222Rn: a public health perspective.

The objective of this study was to assess the lung cancer risk resulting from indoor radon exposure in the province of Quebec, Canada, and to evaluate the efficacy of mitigation measures to reduce this exposure. Concentrations of radon were determined in a representative sample of houses, and the corresponding lung cancer risk estimates were generated using the BEIR IV model, taking into account smoking, residential mobility, and regional variations in radon concentrations. Mean (geometric) radon concentrations in basements (n = 418) and on first floors (n = 319) were, respectively, 34.4 (95% CI-30.6 to 38.8) and 16.5 Bq m(-3) (14.2 to 19.3). A total of 109 deaths from lung cancer are predicted to occur as a result of this exposure in a cohort of 60,000 people. Detecting all residences with high radon concentrations (equal to or above 200 Bq m(-3)) and implementing mitigation measures in each of them would reduce by 4 the number of lung cancer deaths attributable to indoor radon exposure. A reduction of 0.05% in the prevalence of smoking would prevent as many deaths from lung cancer as would radon mitigation. From a public health perspective, in order to reduce mortality from lung cancer, most efforts should be focused on smoking, not on the relatively minor and hardly preventable population risk arising from household radon exposure.