Search

This paper illustrates a real environmental concern and draws attention to the fact that natural processes can mobilize thallium (Tl), a highly toxic metal, which may enter the food chain as a “hidden health killer” with severe health impacts on local human population. Natural processes may be exacerbated by human activities such as mining and farming, and may cause enrichment of Tl in the environment. In geochemically anomalous areas with concentrated levels of Tl in the surface environment (bedrocks, waters, soils, and crops), such as the Lanmuchang area in southwestern Guizhou Province, China, it is essential to establish base-level values and to pay heed to the geological context of “natural contamination,” as high concentrations of Tl in bedrocks/ores (6–35,000 mg/kg) can lead to enrichment of Tl in the aquatic system (0.005–1100 μg/l in groundwaters and 0.07–31 μg/l in surface waters) and soil layers (1.5–124 mg/kg). In sensitive areas such as the Yanshang area of southwestern Guizhou, elevated natural levels of Tl from bedrocks may also cause higher concentrations of Tl in the surface environment, and thus more attention must be paid to geoenvironmental management of human activities if socio-economic catastrophes are to be avoided. Due to high uptake of Tl by crops, Tl can be transferred from soils to crops and remarkably concentrated in food crops. Concentrations of 1–500 mg/kg Tl based on dry weight (DW) were determined in many food crops growing on Tl-contaminated arable soils from the Lanmuchang area. The daily intake of 1.9 mg of Tl from consumed food crops was estimated for the local adult inhabitant of Lanmuchang. Thus, Tl is regarded as a latent health hazard with potential risk of toxicity in humans within areas of “natural” contamination by Tl. Keywords: Thallium, Geoenvironment, Health hazard, Contamination, Chronic poisoning, Guizhou, China

The publisher regrets that in the above article, two references, Xiao et al., 2003b,c, were incorrectly printed. The correctreferences now follow.Xiao T, Guha J, Boyle D. Adverse environmental impact of high thallium content in rocks associated with Au–As–Hg–Tland coal mineralization in southwest Guizhou, China. Geochem: Explor, Environ, Anal 2003b (in press).Xiao T, Guha J, Boyle D, Liu CQ, Chen J. Environmental concerns related to high thallium levels in soils and thalliumuptake by plants in southwest Guizhou, China. Sci Total Environ 2004;318:223–44.