Determination of thorium in the hair and urine of workers and the public in a rare earth mining area

To assess the thorium exposure of the mine workers and the public to a typical rare earth mine and estimate the resultant committed effective dose to them. A total of 79 volunteers were selected in this survey, including 69 mine workers and 10 local residents living about 4 ​km away from the mine site. Urinary samples were collected from 79 volunteers, with 65 hair samples from 57 workers and 8 local residents. The thorium concentrations in urinary and hair samples were determined by using inductively coupled plasma mass spectrometry. The committed effective doses were estimated based on the urinary samples collected and the parameters as recommended by ICRP Publication 137. Thorium concentrations in the samples from the workers ranged from 19.0 to 2388.8 ​ng/g in hair with median of 149.8 ​ng/g, and in urine 18.3–906.1 ​ng/L with median of 59.6 ​ng/L, respectively. The median values of thorium concentrations were 11.8 ​ng/g in hair and 32.40 ​ng/L in urine for the public respectively. The thorium concentrations in urinary and hair samples of the workers were not only higher than those of the residents in the local area, but also than those of non-occupationally exposed populations as reported. The median values of committed effective dose were estimated to be 1.51 ​mSv for the workers and 781 ​μSv for the local residents, respectively. The residents in the local area, and especially the workers, have been subject to long term thorium exposure. More attention should be paid to the radiological hazards of thorium to the workers and local residents.