ISEE/ISEA 2006 Conference Abstracts Supplement: Symposium Abstracts: Abstracts
Radon222 gas is the most important source of natural radioactivity. It is a radioactive noble gas that emanates from the ground. Radon concentrations in outdoor air are low, but inside houses, radon concentrations can reach high levels.
Epidemiologic studies have given conclusive evidence that radon in homes can cause lung cancer. Two large pooled studies in Europe and Northern America show a linear exposure–response relationship (without threshold) between cumulative exposure to radon and lung cancer risk. The consequences of the exposure of the population for the whole population can be described by the population-attributable risk (PAR). To calculate the PAR, 1) the radon concentration in the population, 2) mortality data for lung cancer, 3) assumptions on the excess relative risk (ERR), and 4) model assumptions have to be taken into account.
For this study, we constructed a population-weighted radon distribution for Germany based on radon measurements in living rooms and bedrooms in 27,000 homes from 18 studies; hot spot studies were excluded. Lung cancer mortality was taken from the official statistics and refers to a population of 80 million inhabitants. ERR = 16% per 100 Bq/m3 (corrected for measurement error) was chosen as estimated in the European radon pooling study (7148 cases and 14,208 controls; Darby et al, 2005). PAR is calculated according to the WHO concept of burden of disease. In addition, several scenarios for the effect of reducing the radon concentration by mitigation have been calculated.
The average radon concentration in Germany is 49 Bq/m3, and per year 37,700 persons die of lung cancer. Of these, 1896 cases (PAR 5%) can be attributed to radon. In males, these are 1436 (95% confidence interval: 494–3605) cases, PAR = 5.02% (1.72–12.61%), and in females, 478 (164–1204), PAR = 5.21% (1.79–13.13%). These numbers tend to be smaller than the calculations based on ERR models conducted in miners, which seem to overestimate the PAR.
The most realistic mitigation scenario shows that the reduction of radon in homes above 100 Bq/m3 to concentrations below this cut point saves 302 cases per year (0.8% of all lung cancers) and mitigation above 150 Bq/m3 saves 197 cases per year (0.52% of all lung cancers). However, mitigation of homes above 1000 Bq/m3 only saves a much lower number of 20 cases per year (0.05% of all lung cancers).
This study for the first time gives estimates of PAR based on most recent ERR estimates. Our PAR of 5% for approximately 50 Bq/m3 is clearly lower than the PAR using on the BEIR VI models (which are based on uranium miners). Nevertheless, radon in homes is the most relevant lung cancer risk in the German population after tobacco.