Cadmium, Zinc And Selenium Contents Of The Polished Rice Samples From Some Chinese Open Markets And Their Relevance To Food Safety

Recently,the concentration of heavy metal in cropland soil sharp has been increased due to the development of the industrial and agricultural production, increasing of waste disposals from industrial emission,and agriculture pollution from fertilizers and pesticides.Cd is one of the most important toxic heavy metals while Zn and Se may be beneficial to humanl.The contents of these elments in crops determine the overall effect on human health through food exposure.Rice is a major Chinese food source.However,Cd accumulation ingut from food intake of rice may be of great heath damage because Cd is found intense accumulated in rice grains.Zn and Se are the indispensable micronutrients in human body but there are a large area rice production with low Zn and Se rice paddies.Thus,the level of Cd in relation to Zn and Se content can be an issue for Cd toxicity and essential benefits for people's health requirement.This paper is to dtermine the content range of heavy metals of Cd,Zn and Se in rice grains from overall China and to evaluate the health effects due to intake of these grains.Concerns with sound rice production and sound nutrition pattern will be also given take into account of the results of these elements.The main results obtained are as follows:1.The contents of Cd,Zn and Se of 91 rice samples randomly collected via openmarkets varied in the range of 0.003～1.235 mg/kg,8.320～30.166 mg/kg and 0.004～0.111 mg/kg.There are about 13%of the samples had a Cd content beyond the State Food Security Standards(0.2 mg/kg).2.7%of the rice samples is likely to exert potential health hazards due to the exposure of Cd if the R_fD(WHO)(7μg·kg^-1·d^-1) value as a reference,while it is 70%if the R_fD(USEPA)(1μg·kg^-1·d^-1) value as a reference.Rice samples of Indica could have a much higher Cd content level than those of Japonica,suggesting a far higher Cd exposure hazard of Indica rice than the Japonica.In addition,the content levels of Zn and Se in the rice samples prove generally rather low,beyond the recommended values for healthrequirement through the regular dietary intake.3.There indeed exists positive correlation between the content of Cd and that of Cd/Zn,as well as between Se content and that of Se/Zn ratio,which indicates a slight accumulation of Zn in relation to Cd and Se.However,on the whole,89%of the rice samples have a lower Cd/Zn ratio than the critical value of 0.015 proposed by American scientists.In addition,samples with high Cd content may not be necessarily beyond the regular high Cd/Zn ratio.Therefore,the present research can be used as a valuable reference to further studies for the potential effects of the toxic heavy metal content in rice on the human health as well as their relation to the soil-crop-food security.