[Evaluating the Health Risks of Thallium in Farmland Soil Through the Food Chain]

To explore the health risks brought by the transfer of thallium (Tl) in farmland soil through the food chain to planted crops (taking sweet potatoes as an example), three areas with similar geographical environments and planting methods but different Tl contents were selected for sample collection. This study indicated that Lianguang Village and Gaozhai Village in Pinghe, Zhangzhou, belonged to the farmland surrounding the Huashanxi River Basin and had higher Tl levels, with Tl contents in the soil ranging from 0.413 to 0.700 mg·kg^-1. The Tl content in Xibian Village, Nanjing, Zhangzhou ranged from 0.283 to 0.337 mg·kg^-1, which was lower than the average concentration of 0.49 mg·kg^-1 in the Earth's crust. However, none of these soils exceeded the maximum limit specified for agricultural soil (1 mg·kg^-1). Tl content in sweet potatoes ranged from 0.004 45 to 0.032 9 mg·kg^-1, with an average of 0.015 9 mg·kg^-1. Tl content in sweet potatoes was far below the human safe consumption standard of 0.3 mg·kg^-1. An in vitro bionic gastrointestinal digestion and absorption method was employed to study the digestion and absorption effects of Tl and other trace metals after ingestion of sweet potatoes, which had absorbed Tl through the food chain from the soil. The bioaccessibility and bioavailability of Mg, K, Ca, Mn, Fe, Cu, Cr, Cd, and Pb in the chyme after gastrointestinal digestion of sweet potatoes were determined. There was a strong correlation between the Tl content in sweet potatoes and the bioaccessibility and bioavailability of K, Ca, and Fe (R²=0.956 4-0.995 3, P < 0.05), while no correlation was found between the Tl content and the bioaccessibility and bioavailability of Mg, Mn, Cu, Cr, Cd, and Pb. The results indicated that Tl could be transferred from farmland soil to cultivated crops, affecting human health through the food chain. Even low doses of Tl in food had a competitive inhibitory effect on the digestion and absorption of K, Ca, and Fe, leading to metabolic disturbances of trace elements. Therefore, measures must be taken to reduce the bioavailability of Tl in soil to mitigate its impact on human health.