and others 1994). The BEIR VI analysis used updated versions of the 11 miner cohorts, so the model results are quite similar. The parameters estimated by the BEIR VI committee are also provided in table 5.6.

The NCI report summarized the calculated deaths in the US population from the assumed average exposure of 46 Bq m-3. Its calculated value was 15,000 deaths, consisting of 10,000 deaths in smokers and 5,000 in nonsmokers. This estimate of the attributable risk is derived from the model of lung cancer risk, a distribution of radon exposures, and the lung cancer and overall mortality rates (National Research Council 1999; NIH 1994).

Epidemiology of Childhood Exposure and Lung-Cancer Risk

It is apparent that leukemia and breast cancer are more frequent in people exposed to radiation in childhood than in those exposed as adults (National Research Council 1990a). Concern has been expressed that the same might be true for lung cancer that results from exposure to radon and its decay products at early ages.

Some data are available on occupational exposure to high radon concentrations in childhood. Lubin and others (1990) analyzed data on Chinese tin miners in the Yunnan province. Of exposed workers, 37% started employment under the age of 13; in this group, the risk coefficient for lung cancer was 1.2% WLM-1. For those first employed over the age of 18, the risk coefficient was 2.9% WLM-1. Later and more complete information on the entire cohort (Xuan and others 1993) showed heterogenous results with no pattern that would support the notion that children are at higher risk. It appears that children are not a particularly sensitive population.

Tentatively, the lower risk coefficient for children than for adults reported by Lubin and others (1990) suggests that the reduction in lung-cancer risk with time after exposure might be effective in children. The fact that lung cancer does not appear at a substantial rate in any population before the age of 40, permits a substantial interval for risk reduction for exposure in childhood.

Environmental and Domestic Epidemiology

Lung-cancer excess (above that expected from smoking) in the underground-miner populations has been demonstrated conclusively. Combining that and the knowledge that some homes have radon and daughter concentrations near or above those found in historical mines, it seems virtually certain that environmental radon is responsible for some lung cancer in the general population.

There are more than 20 environmental epidemiologic studies of radon exposure to determine whether health effects can be documented directly (National Research Council 1999; Neuberger and others 1996; Neuberger 1989, DOE/CEC



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