Multimedia tungsten contamination and health risk from tungsten mining and refining

Tungsten (W) is an emerging contaminant present in environments mainly as a result of W production and use. China ranks first in the world in terms of W production and reserves. Environmental W pollution of W mining and refining and its human health risks have not been understood well. This study aims to examine W from sources to environments, to edible plants, and to human and assess its human health risk in a W mining and refining area. W mining and refining solid wastes and wastewater and downstream soil, river water and sediment, and plants were collected and analyzed for W. The results showed that median W concentrations were 654.4, 140.4, and 12.2 mg/kg in the solid waste, sediment, and soil and 46.6, 5.6, and 0.4 µg/L in the wastewater, river water, and groundwater, respectively. Developed W geochemical baseline showed that the median concentrations of anthropogenic W were 136.0 and 7.9 mg/kg in the sediment and soil, respectively. These results reveal W pathways from its mining and refining wastes to downstream river and then to soil via runoff and irrigation. W concentrations in plants ranged from 0.03 to 69.1 mg/kg, with higher concentrations in leaf vegetables than in fruit vegetables, rice grains, and citrus fruit. W enrichment factors from soil to root were one order of magnitude lower than its transfer factors from root to shoot except rice. The potential noncarcinogenic risk of total W exposure via soil, water, rice, vegetable, and fruit ingestion would occur at 0.462 and 0.640 probabilities for local adults and children, respectively; which was dominated by vegetable and rice ingestion. Considering soil W bioaccessibility and percentages of home-grown vegetable and rice ingestion out of total vegetable and rice ingestion, total W exposure would lead to the noncarcinogenic risk at 0.352 and 0.497 probabilities for local adults and children, respectively; which was dominated by vegetable. It is concluded that environmental W contamination and its enrichment in edible plants in the surrounding and downstream areas of W mining and refining would pose health risks to residents. It is suggested that oral W bioaccessibility in soils and edible plants should be studied in future to accurately assess oral W exposure as well as its health risk.