Transformation of lung cells from inhalation of radon daughters in dwellings: a preliminary study

There is now world-wide concern for the quantification of lung cancer risk due to indoor radon, but the recent estimates are based on epidemiological studies of miners alone. The present attempt is a preliminary study of the alteration of lung stem cells irradiated by alpha particles emitted by radon daughters. Local energy deposited has been calculated for alpha particles, emitted from radon daughters lining the mucous layer in the respiratory tracts. This calculation has then been followed by dose evaluation and estimation of transformation of lung cells as a function of age. Mean life span of the stem cells was varied between 5 and 45 years to simulate living conditions in different environments. The cumulative fraction of transformed cells after 40 and 70 years has been calculated for radon concentration in the range 23-230 Bq/m3. Increase of the fraction of transformed cells with radon concentration was exponential. It has been assumed that causes other than radiation increase the rate of cell death of mature and stem lung cells, and hence the turnover of stem cells to replace them. It is concluded that the rate of transformation of cells is small for low radon concentration even late in age for non-polluted environments. For radon concentrations of 50 and 100 Bq/m3 the fractions of transformed cells are 0.2 and 6 per cent, respectively for an exposure time of 70 years.