研究生知识库

水稻是全球食用最广泛的粮食作物，是世界一半以上人口的主食。水稻的安全问题与全球居民的健康息息相关。本世纪初，研究者发现水稻具有超积累甲基汞的能力，由于汞具有是全球性传输的污染物且具有很强的神经毒性，水稻汞污染问题迅速成为全球汞研究关注的热点问题。近年来，随着人们认识到食用稻米是我国汞污染地区人群甲基汞暴露的重要途径，公众的对水稻汞（尤其是甲基汞）关注日益增加。水稻汞污染问题使公众，尤其是大米消费人群，陷入疑惑和恐慌—“我们吃的大米甲基汞含量是多少，是否安全？”因此系统地研究水稻中汞和甲基汞含量分析居民暴露风险回答公众关切并消除公众的恐慌和疑惑是十分必要的。本研究系统性地研究中国市场大米、不同典型污染区（秀山汞矿区、万山汞矿区、煤矿区、燃煤电厂、铅锌冶炼区、水泥厂/铝厂/铝矿复合污染区）大米中总汞和甲基汞含量，评估居民暴露后的健康风险。总结研究数据系统性的评估我国各个污染程度大米的总汞和甲基汞水平，并基于蒙特卡洛模型和单区室药代动力学模型预测居民食用不同大米之后的健康效应，取得了以下认识：中国市场大米总汞含量平均为3.97±2.33 μg/kg（0.64-31.7 μg/kg）；甲基汞平均含量1.37±1.18 μg/kg（范围：0.020-19.0 μg/kg），其中有<0.5%的样品总汞含量超出了国家规定的大米总汞含量限值标准（20 μg/kg）。我国华中和华南地区居民大米甲基汞和无机汞暴露水平显著高于其他地区。不同性别-年龄段居民食用大米后甲基汞暴露水平均处在安全范围内；甲基汞和无机汞最高的暴露水平都在儿童组获得（男：4-7岁；女：2-4岁）。随着我国实施严格的汞污染控制政策，环境中汞的排放量已经呈下降趋势，水稻中总汞和甲基汞的浓度呈现下降趋势，表明我国居民面临的水稻汞暴露逐渐降低。水稻中总汞和甲基汞含量都呈现：汞矿区>煤矿区>燃煤电厂>铅锌冶炼区>水泥厂/铝厂/铝矿复合污染区。汞矿区大米总汞超标最严重，煤矿区、燃煤电厂、铅锌冶炼地区存在个别超标现象。汞矿区水稻存在甲基汞超出10.2 ng/g，部分甚至超出国家总汞标准限值（20 ng/g）；其他典型区域（煤矿区、燃煤电厂、铅锌 冶炼地区、水泥厂/铝厂/铝矿复合污染区）甲基汞水平整体较低。居民食用汞矿区大米之后面临超出RfD值的高甲基汞暴露风险，而食用来自其他典型区域的大米甲基汞暴露水平较低。纵观我国居民各种大米来源，我国大米总汞和甲基汞含量最高的为汞矿区，显著高于工业区和非污染区。汞矿区对应的甲基汞暴露水平存在高于甲基汞参考剂量值的情况，食用其他类型种植区的大米不会面临超出RfD值的风险。单区室药代动力学模拟结果表明，食用汞矿区大米之后血液和头发甲基汞含量上升（头发：1.81 μg/L；血液：1.04 μg/g）显著高于食用工业区（血液：0.25 μg/L；头发：0.144 μg/g）和非污染区大米血液和头发甲基汞浓度的增加量（血液：0.214 μg/L；头发：0.123 μg/g）。

Rice is the most widely consumed food crop in the world, the staple food for more than half of the world’s population. The safety of rice is highly closed to the health of global residents. At the beginning of this century, researchers found that rice has the ability to accumulate methylmercury (MeHg). Because mercury (Hg) is a globally transported pollutant and has strong neurotoxicity, the problem of mercury pollution in rice has become a hot issue. In recent years, with the recognition that rice consumption is the major pathway of human MeHg exposure, public concern to rice Hg (especially MeHg) is increasing. It pulled the public into a panic and confusion that “What is the level of MeHg in rice we eat, and is it safe to people ?” Therefore, it is necessary to investigate total Hg (THg) and MeHg of rice we consume systematically, and estimate associated Hg exposure of residents to address the public concerns and panic.This study systematiclly investigate the concentrations of THg and MeHg in rice from the Chinese market, different typical polluted areas (Xiushan Hg mining area, Wanshan Hg mining area, coal mining area, coal-fired power plant, Pb-Zn smelting area, cement plant/aluminium plant/aluminium mine complex polluted area). On the basis of Monte Carlo model and single comaprtment pharmacokinetic model, the associated exposure risk and health effects were simulated. The following conclusions can be obtained:The geometric mean THg and MeHg concentrations of Chinese commerical rice were 3.97±2.33 μg/kg (range: 0.64-31.7 μg/kg) and 1.37±1.18 μg/kg (range：0.020-19.0 μg/kg), respectively. Moreover,<0.5% of them exceeded the Chinese national standard for rice THg concentration (20 μg/kg). Exposure levels of rice MeHg and inorganic Hg (IHg) for central and southern Chinese were significantly higher than those of people from other areas. The exposure levels of MeHg and IHg in different sex-age gender groups were with the safe levels, and the highest of them were obtained in younger groups (male: 4-7 years; female: 2-4 years). With the implementation of strict Hg pollution control policies in China, Hg emissions in the environment have shown a downward trend, and the concentrations of THg and MeHg in rice have shown a downward trend, suggesting that the associated rice Hg exposure of Chinese residents is gradually decreasing.For different typical areas, the concentrations of THg and MeHg in rice followed the order: Hg mining areas > coal mining area > coal-fired power plant > Pb-Zn smelting area > cement plant/aluminium plant/aluminium mine complex pollution area. The THg in rice from Hg mining area had the highest exceeding rate, while only several samples of coal mining area, coal-fired power plant and Pb-Zn smelting area exceeded the standard limit of THg. The methylmercury level of rice in mercury mining area exceeds 10.2 ng/g, partly even exceeded the national THg standard limit (20 ng/g); the MeHg levels of rice from other typical areas (coal mining area, coal-fired power plant, Pb-Zn smelting area, cement plant/aluminium plant/aluminium mine complex pollution area) were generally low. Residents who consume rice from Hg mining areas will confront high MeHg exposure risk (beyond RfD value), while those who eat rice from other typical areas meet a low MeHg exposure level.Throughout all types of producing areas, the highest geometric mean concentration of rice THg and MeHg were found in Hg mining areas, which were significantly higher than those in industrial and non-polluted areas. The corresponding average exposure level of MeHg in Hg mining areas was higher than the RfD value of MeHg, while after consuming rice from other types of producing areas would not meet the risk of exceeding RfD value. The results of single compartment pharmacokinetic simulation showed that the MeHg in blood and hair increased significantly (hair: 1.81 ug/L; blood: 1.04 ug/g) after consuming rice from Hg mining areas than that from industrial areas (blood: 0.25 ug/L; hair: 0.144 ug/g) and non-polluted areas (blood: 0.214 ug/L; hair: 0.123 ug/g).