中国水稻生产中Cd吸收及其健康风险的有关问题

环境中Cd的迁移及其对生物和人的毒性问题是环境科学关于重金属行为研究的重点和热点问题。土壤-植物(作物)-食品-人的迁移途径在人类对环境Cd的暴露中占主要地位,发达国家对土壤和食品中Cd的限量作出了严格的规定。主要对最近十多年来关于水稻Cd吸收与籽粒积累及其影响因素的研究进行了综述,分析中国水稻生产中存在稻米Cd积累与食物健康风险问题,讨论了其与我国水稻生产的发展趋势、主产区稻田的土壤环境问题的关系。

Issues of Grain Cd Uptake and the Potential Health Risk of Rice Production Sector of China

The transfer of Cd in the environment and the toxicity has been one of the foci for studies of heavy metal behaviors in environmental sciences. Cd transfer through soil-plant-food-human has been ranked as the dominant pathway for human Cd exposures. Very strict guideline values have been proposed or established in regulations of soil and food in the developed world. In this paper, the research findings on Cd uptake by rice grains and the major controlling factors are overviewed from literature at home and abroad. The trends of enhanced Cd uptake and accumulation in rice grains and the potential health risk especially for subsistence diet consumers are analyzed and discussed, taking into account the cultivars innovation, soil conditions of acid reaction and low organic carbon as well as the expansion of Cd-polluted paddys in China. While the toxicity of food Cd depends not only on the content but also on the Cd-Zn relations varying with the different types of crops, rice has been well accepted as a particular crop high in Cd affinity and Zn depletion in the grains among the major staple crops. Cd transfer from paddy to rice grains is shown affected by cultivars and genotypes, soil Cd level and the availability, as well as the interaction of both soil chemistry and physiology of genotypes. The high yielding rice cultivars such as hybrid and super rice tend to favor Cd uptake and Zn depletion in grains as evidenced both by pot experiments and field survey studies. Such process is significantly enhanced in acid paddies, which raises the serious health risk for subsistence diet farmers in South China rice area. The potential risk may become severely great under the existing paddy acidification, extending soil Cd pollution and extensive cultivation of super rice cultivars as well as increasingly drainaged paddies after rice flowering due to water scarcity in the future. This should be seriously concerned in China's rice production sector as rice grains with enhanced Cd and Zn depletion may possess high toxicity when entering human gut. It is strictly suggested that screening of genotypes low in Cd uptake for rice breeding and innovation of farm practices depressing Cd uptake and remediation of Cd-polluted paddies should be urgently conducted in alliance with food consumption modification for farmers. For meeting the demand of food supply for the increasing population, regulation of soil environment quality, protection of paddies from Cd pollution and rational cultivation of cultivars with high Cd affinity deserve urgent performance in China.