Study of the health effects exposure to thorium dusts of the miners in China

Objective: To investigate the health effects of the miners in Baiyun Obo Rare Earth Iron Mine after long-term exposed to high air concentrations of thorium-containing rare-earth dusts and short lived thoron daughters. Methods: By using the negative high voltage exhaled thoron progeny measurement system. Results: Epidemiological study showed that the SMR of lung cancers of the dust-exposed miners was much higher than that of the controls. The difference between these two SMRs was highly significant. Conclusion: It was the first evidence that the dust-exposed miners after long-term (more than 30 years) exposed to high air concentrations of thorium containing rare-earth dusts and thoron short-lived progeny could induced excess lung cancer. The synergic effects of long history smoking and the γ exposure in mining area could not be excluded