Xiao Tangfu, Guha Jayanta, Boyle Dan, Liu Cong-Qiang, Zheng Baoshan, Wilson Graham C, Rouleau Alain, Chen Jingan
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China.
Environ Int. 2004 Jun;30(4):501-7. doi: 10.1016/j.envint.2003.10.004.
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 microg/l in groundwaters and 0.07-31 microg/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.
本文阐述了一个切实存在的环境问题，并提请人们注意这样一个事实：自然过程能够使铊（Tl）这种剧毒金属进入可移动状态，它可能作为“隐藏的健康杀手”进入食物链，对当地人群的健康产生严重影响。采矿和农业等人类活动可能会加剧自然过程，并导致环境中铊的富集。在中国贵州省西南部的滥木厂地区等地球化学异常区域，地表环境（基岩、水体、土壤和农作物）中铊的含量较高，确定背景值并关注“自然污染”的地质背景至关重要，因为基岩/矿石中高浓度的铊（6 - 35000毫克/千克）会导致水生系统（地下水中0.005 - 1100微克/升，地表水中0.07 - 31微克/升）和土壤层（1.5 - 124毫克/千克）中铊的富集。在贵州省西南部的岩上地区等敏感区域，基岩中自然铊含量升高也可能导致地表环境中铊浓度升高，因此，如果要避免社会经济灾难，就必须更加关注人类活动的地质环境管理。由于农作物对铊的吸收能力较强，铊可以从土壤转移到农作物中，并在粮食作物中显著富集。在滥木厂地区受铊污染的耕地上种植的许多粮食作物中，以干重计铊的含量为1 - 500毫克/千克。据估计，滥木厂当地成年居民通过食用粮食作物每日摄入铊的量为1.9毫克。因此，在铊“自然”污染区域，铊被视为一种潜在的健康危害，对人类具有潜在的毒性风险。
