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Health effects following long-term exposure to thorium dusts: a twenty-year follow-up study in China

Published online by Cambridge University Press:  17 June 2005

X. A. Chen
Affiliation:
National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, P.O. Box 8018, Beijing 100088, P.R. China
Y. E. Cheng
Affiliation:
National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, P.O. Box 8018, Beijing 100088, P.R. China
H. Xiao
Affiliation:
National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, P.O. Box 8018, Beijing 100088, P.R. China
G. Feng
Affiliation:
Hospital of Baiyun Obo Rare-earth Iron Mine Baiyun Obo, Baotou 014080, P.R. China
Y. H. Deng
Affiliation:
Hospital of Baiyun Obo Rare-earth Iron Mine Baiyun Obo, Baotou 014080, P.R. China
Z. L. Feng
Affiliation:
Hospital of Baiyun Obo Rare-earth Iron Mine Baiyun Obo, Baotou 014080, P.R. China
L. Chen
Affiliation:
National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, P.O. Box 8018, Beijing 100088, P.R. China
X. M. Han
Affiliation:
Hospital of Baiyun Obo Rare-earth Iron Mine Baiyun Obo, Baotou 014080, P.R. China
Y. J. Yang
Affiliation:
National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, P.O. Box 8018, Beijing 100088, P.R. China
Z. H. Dong
Affiliation:
National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, P.O. Box 8018, Beijing 100088, P.R. China
R. Zheng
Affiliation:
National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, P.O. Box 8018, Beijing 100088, P.R. China
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Abstract

A twenty-year follow-up study was carried out at Baiyun Obo Rare-earth Iron Mine in China, This mine has been mined since 1958. Its ore contains 0.04% of ThO2 and 10% of SiO2. The purpose of this study is to investigate possible health effects in dust-exposed miners following long-term exposure to thorium-containing dusts and thoron progeny. By using the negative high voltage exhaled thoron progeny measurement system to estimate the miner’s thorium lung burden. The highest thorium lung burden among 1 158 measurements of 638 miners was 11.11 Bq. The incidence of stage 0+ pneumoconiosis was increased among dust-exposed miners. An epidemiological study showed that the lung cancer mortality of the dust-exposed miners was significantly (p < 0.005) higher than that of the non-exposed group. It is suggested that the difference results in the long-term exposure to thorium-containing dusts (carcinogens are ThO2 and SiO2) and thoron progeny. This is the first evidence in humans of the carcinogenicity after long-term inhalation of thorium-containing dusts and thoron progeny. The total person-years of observation for the dust-exposed miners and the controls were 62 712 and 34 672 respectively.

Type
Research Article
Copyright
© EDP Sciences, 2004

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