Recent advances in understanding the risk due to the inhalation of radon daughters

Many of the estimates of the cancer risk due to radon daughter inhalation, made on the basis of epidemiological data available in the late 1960's, are becoming obsolete. Also, as might be expected, these earlier estimates appear to be somewhat low. Exposed persons have continued to die as the length of the followup period has continued. The 1972 BEIR Report updated and detailed results published in Joint Monograph No. 1, Radon Daughter Exposure and Respiratory Cancer by Lundin, Wagoner and Archer. As in all BEIR estimates, the risk of lung cancer was assessed in two ways, absolute risk, or the number of excess cancers expected per 106 organ rem per year at risk and relative risk, and the proportion of excess cancer incidence observed per rem compared to the incidence in an unexposed control population. For the case of U.S. uranium miners, the absolute risk estimated in 1972 was 1 excess lung cancer per 106 organ rem per year at risk. Archer and others have monitored uranium miner deaths since the BEIR Report was prepared and also re-examined criteria for accepting some of the death data previously used. This has led to revised conclusions. The most recently published estimate of the risk to U.S. uranium miners was published in the 1976 NAS report, Health Effects of Alpha-Emitting Particles in the Respiratory Tract, prepared by a BEIR ad hoc committee to investigate the hot particle problem. The conclusion reached in this report is that the previous BEIR estimate was low by a factor of two and that a better estimate of the absolute risk is two lung cancers per 106 organ rem per year at risk. Other recent studies using non U.S. data are reviewed that also appear to support a higher risk due to radon daughter inhalation