Evaluating health risk indicators for PTE exposure in the food chain: evidence from a thallium mine area

Thallium (Tl) has a high relative toxicity and is easily taken up by plants, but little is known about wider relationship with co-contaminants and in typical domestic food crops. We evaluated the extent of contamination, evidence for bioaccumulation in typical food crops (Chinese cabbage, green cabbage, chili, carrot, corn and rice), and subsequent contribution to health risks for 7 elements (Tl, As, Cd, Pb, Ni, Cu, Zn) associated with soil contamination in the local soils of a major Tl mine in Guizhou, southwest China. Derivation of relevant risk indicators from the bioconcentration factor (BCF), comprehensive crop pollution index (P), the target hazard quotient (THQ) (element), and the hazard index (HI) (all elements) were assessed as tools to support the evaluation. Our results showed that the degree of contamination and uptake by crops in the study area were: root vegetables > leaf vegetables > fruit vegetables > cereals. With the exception of corn, other crops pose a significant risk to human health which is dominated by the Tl content. In addition, the Cu in carrot samples suggests hyperaccumulation at the site and poses a high risk to human health. The results provide direct evidence of significant food chain exposure and identifies the need for Tl-focused management of soil/plant interaction and that strategy needs to also understand the implications for behavior of co-contaminants in the area.