Abstract
While health risk of exposure from radon and its decay products has been estimated based on epidemiological studies for miners, it is required that risk assessment for general public should be based on study conducted in general environment. Recently, the pooled analyses of North American and European epidemiological studies have been conducted and it is pointed out that the lung cancer risk increased significantly even at relatively low levels of radon concentration. Yunnan province, China is the largest tin-producing district in the world. Although the results of epidemiological study of Yunnan tin miners was employed in BEIR-_IV_ report, there are some issues on dose assessment which might lead to lower risk presumption than the other studies. In order to examine the feasibility of epidemiological survey of residential radon in Yunnan, radon, thoron and their decay products measurements were conducted in this study.
Radon and thoron decay products were measured in 100 dwelling of the farm village and 50 of the urban area in Gejiu city, Yunnan in 2004-2006.
The annual dose from indoor radon and thoron decay products for the local populations was estimated based on the several models and assumptions, indicating the dose from thoron decay products could be higher than that from radon decay products. Those results suggest the importance of thoron dose assessment in epidemiological survey of residential radon, though there remain some uncertainties in dose assessment for thoron.
