Atmospheric thorium pollution and inhalation exposure in the largest rare earth mining and smelting area in China

Exposure to radionuclide thorium (Th) has generated widespread public concerns, mainly because of its radiological effects on human health. Activity levels of airborne Th-232 in total suspended particulate (TSP) were measured in the vicinity of the largest rare earth mine in China in August 2012 and March 2013. The mean activity concentrations of Th-232 in TSP ranged from 820 mu Bq m(-3) in a mining area in August 2012 to 39,720 mu Bq m(-3) in a smelting area in March 2013, much higher than the world reference of 0.5 mu Bqm(-3). Multistatistical analysis and Kohonen's self-organizingmaps suggested that Th-232 in TSP was mainly derived from rare earth mining and smelting practices. In addition, personal inhalation exposures to Th-232 associated with respirable particulate (PM10) were also measured among local dwellers via personal monitoring. The mean dose values for different age groups in the smelting and mining areas ranged from 97.86 to 417 mu Sv year(-1) and from 101.03 to 430.83 mu Sv year(-1), respectively. These results indicate that people living in the study areas are exposed to high levels of widespread Th-232. (C) 2016 Elsevier B.V. All rights reserved.