Lung cancer and alpha radiation.

The considerable radiosensitivity of the human lung together with the highly localized alpha-doses in the bronchial and pulmonary regions from naturally occurring and man-enhanced radon decay products make the respiratory tract the most critical organ for cancer from exposure to ionizing radiation in our environment. From indoor radon, the tracheobronchial region of the lung generally receives radiation doses which are at least an order of magnitude above the total dose to any other organ. Excess lung cancer deaths found in epidemiological studies on heavily exposed populations of miners can be fitted reasonably well to a relative risk model, when declines in relative risk with both age at risk evaluation, and time since exposure, are incorporated. Smoking seems to act synergistically. A comparison of the major radon risk projections shows considerable discrepancies in the best estimates of risk, indicating that the uncertainties remain large.