The significance of dose rate in assessing the hazards of domestic radon exposure.

Both miner-based epidemiological data and animal studies suggest that lung cancer induction from radon-progeny alpha-particle exposure depends on the exposure rate, and increases as the exposure rate decreases. This phenomenon has been interpreted to imply that radon risks per unit dose from domestic exposure (which occur at low exposure rates) will be underestimated by risk estimates derived from miner studies (which are at higher exposure rates). There is, however, another variable affecting this phenomenon, namely the absolute cumulative exposure to radon progeny. On basic biophysical grounds, it is argued that when the cumulative exposure is sufficiently low that multiple traversals of target cells are rare, the exposure rate effect disappears. This is the case for typical domestic radon exposures but not for most miner exposures; thus, although risk estimates from miner data refer to higher dose rates, based on dose rate consideration alone they may well overestimate, rather than underestimate, domestic radon risks. Although the data are limited, both miner-based epidemiological data and animal studies appear to follow the trend described here.