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

摘要

Exposure to radionudide thorium (Th) has generated widespread public concerns, mainly because of its radiological effects on human health. Activity levels of airborne ~(232)Th in total suspended paniculate (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 ~(232)Th in TSP ranged from 820 μBq m~(-3) in a mining area in August 2012 to 39,720 μBq m~(-3) in a smelting area in March 2013, much higher than the world reference of 0.5 μBq m~(-3). Multistatistical analysis and Kohonen's self-organizing maps suggested that ~(232)Th in TSP was mainly derived from rare earth mining and smelting practices. In addition, personal inhalation exposures to ~(232)Th associated with respirable particulate (PM_(10)) 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 μSv year~(-1) and from 101.03 to 430.83 μSv year~(-1), respectively. These results indicate that people living in the study areas are exposed to high levels of widespread ~(232)Th.