[en] Full text: The purpose of this paper is to present the thorium lung burden and its health effects among the workers of Huamei Rare-earth Refinery Factory, Baotou, China. The methods used is a combination between exhaled thoron activity measurement and the physical examination (peripheral blood counts, hepatic function tests, lung function tests, chest X-ray radiograph) as well as the measurement of dust concentrations, radon and thoron short lived progeny concentration in the air of the workshops. The results showed that the four workshops are thought to be the radiological workplaces. The dust air concentrations in different workshops range from 1.34∼8.17 mg/m³. The average α potential energy value of radon short-lived progeny are in the range from 24 to 285 MeV/L; while the average α-progeny are in the range from 159 to 5972 MeV/L. The thorium lung burdens of 9 dust-exposed workers are higher than one investigation level (2.22 Bq) and the highest one is 3.33 Bq. The results of radiography, hematological parameters and hepatic parameters for the dust exposed workers examined are all within the normal range, while the lung function of 27 cases among the 91 dust exposed workers are abnormal. Our conclusion is that the radiological protection problems are existed in rare-earth refinery factory, mainly the high thorium-containing dust air concentration and the high α potential energy of the thoron short-lived progeny in the air of different workshops. Ventilation should be improved. Long-term follow-up study is necessary. (author)