Analysis On Heavy Metal Content In Rice Of China And Its Health Risk Evaluation

Rice ranks top in the foodstuffs of China. Compared with other foodstuffs, rice has more nutrients, wider planting area and higher production rate. Therefore, it has become the main food loved by Chinese people for a long time. However, with the continuous industrial development and environmental contamination, rice is contaminated by heavy metals from the industry and environment. Heavy metal pollutants in the soil, water and air from rice planting areas go into rice and accumulate in its fruits, which lead to heavy metal contents in rice products, exceeding the maximum allowable concentration (GB2715-2005) and may harm the health of the people eating them. This study detected heavy metal contents of rice from seven main rice-producing areas (Northeast of China, Northwest of China, Northern China, Central China, Eastern China, Southern China and Southwest of China), produced rice starch and rice protein and analyzed the lead distribution in them. The major results are as follows:1. Investigation on heavy metal content in rice and its health risk evaluation. According to limit contents of heavy metals from hygienic standard for grains (GB2715-2005), the results of detecting heavy metal contents in92rice samples from seven main rice-producing areas of China showed that four, three and two samples exceeded the maximum allowable concentration (GB2715-2005) of Pb, Cd and As respectively and no sample exceeded the maximum allowable concentration (GB2715-2005) of Hg. In the92samples studied the maximum allowable concentration (GB2715-2005) of Pb, Cd and As was exceeded by4.3%,3.3%and2.2%respectively. In conclusion, heavy metal contents in rice from major rice-producing areas in China were safe. Due to single pollution index evaluation method, the results of evaluating heavy metal pollution showed that different pollution levels by heavy metals existed in different species of rice. The results also showed that three species of rice were polluted by Pb, but there was no pollution according to synthetic pollution index evaluation. Considering the health risk index evaluation, a majority of testing samples had low-level health risk and they could be considered safe for people to eat.2. Lead distribution in rice and edible safety evaluation on rice products and raw materials. This study adopted traditional method of protein extraction "alkali extraction" to separate15species of rice starch and protein simultaneously and made rice starch and rice protein products. The results showed that in the condition of CNaOH=0.1mol/L, pH=5.2, the percentage of starch and protein extraction in rice was57.7%～69.8%and3.92%～5.76%respectively, lower than their theoretical values. Besides that, the results of rice starch and protein extraction were different in different species. Rice starch and protein made in this study were research materials, and their Pb contents were detected in order to explore Pb distribution in main components of rice. The results showed that Pb was not detected in rice starch and Pb content in rice proteins was50%that of rice. Besides that, there were significant differences of Pb distribution among different species, types and ranks of rice. Pb contents in nonglutinous rice were higher than that in long-shaped rice, and the extent of Pb distribution in rice proteins became more severe with the increase in rank. The results in this study provide basic data for research on heavy metal pollution and its exsiting forms in rice of China, scientific references for continuing research on regularity of heavy metal accumulation in rice ingredients and powerful support for safe production of rice and its quality and safety control, benefiting healthy development of industries using rice as raw material.