Human Health Risk Assessment and Safety Threshold of Harmful Trace Elements in the Soil Environment of the Wulantuga Open-Cast Coal Mine

In this study, soil samples were collected from a large-scale open-cast coal mine area in Inner Mongolia, China. Arsenic (As), cadmium (Cd), beryllium (Be) and nickel (Ni) in soil samples were detected using novel collision/reaction cell technology (CCT) with inductively-coupled plasma mass spectrometry (ICP-MS; collectively ICP-CCT-MS) after closed-vessel microwave digestion. Human health risk from As, Cd, Be and Ni was assessed via three exposure pathways—inhalation, skin contact and soil particle ingestion. The comprehensive carcinogenic risk from As in Wulantuga open-cast coal mine soil is 6.29–87.70-times the acceptable risk, and the highest total hazard quotient of As in soils in this area can reach 4.53-times acceptable risk levels. The carcinogenic risk and hazard quotient of Cd, Be and Ni are acceptable. The main exposure route of As from open-cast coal mine soils is soil particle ingestion, accounting for 76.64% of the total carcinogenic risk. Considering different control values for each exposure pathway, the minimum control value (1.59 mg/kg) could be selected as the strict reference safety threshold for As in the soil environment of coal-chemical industry areas. However, acceptable levels of carcinogenic risk are not unanimous; thus, the safety threshold identified here, calculated under a 1.00 ˆ 10 ́6 acceptable carcinogenic risk level, needs further consideration.