Calculation of the 1995 lung cancer incidence in the Netherlands and Sweden caused by smoking and radon: risk implications for radon

A two-mutation carcinogenesis model was used to calculate the expected lung cancer incidence caused by both smoking and exposure to radon in two popul ations, i.e. those of the Netherlands and Sweden. The model parameters were taken from a previous analysis of lung cancer in smokers and uranium miner s and the model was applied to the two populations taking into account the smoking habits and exposure to radon. For both countries, the smoking histo ries and indoor radon exposure data for the period 1910-1995 were reconstru cted and used in the calculations. Compared with the number of lung cancer cases observed in 1995 among both males and females in the two countries, t he calculations show that between 72% and 94% of the registered lung cancer cases may be attributable to the combined effects of radon and smoking. In the Netherlands, a portion of about 4% and in Sweden, a portion of about 2 0% of the lung cancer cases (at ages 0-80 years) may be attributable to rad on exposure, the numbers for males being slightly lower than for females. I n the Netherlands, the proportions of lung cancers attributable to smoking are 91% for males and 71% for females; in Sweden, the figures are 70% and 5 6%, respectively. The risk from radon exposure is dependent on gender and c igarette smoking: the excess absolute risk for continuous exposure to 100 B q m(-3) ranges between 0.003 and 0.006 and compares well with current estim ates, e.g. 0.0043 of the International Commission on Radiological Protectio n (ICRP). The excess relative risk for continuous exposure to 100 Bq m(-3) shows a larger variation, ranging generally between 0.1 for smokers and 1.0 for non-smokers. The results support the assumption that exposure to (indo or) radon, even at a level as low as background radiation, causes lung canc er proportional to the dose and is consistent with risk factors derived fro m the miners data.