[Variation of Cd, Zn and Se contents of polished rice and the potential health risk for subsistence-diet farmers from typical areas of South China].

In this study, a total of 70 polished rice samples were randomly collected at agro-product markets from some typical regions of South China. Their contents of Cd, Zn and Se were determined by atomic adsorption spectrophotometers (AAS) and atomic fluorescence spectrometry (AES) respectively. The variation of the contents with rice areas was described in terms of soil conditions and the potential health risk by food exposure to these rice rains for subsistence-diet fanners is discussed. Over 70% of the total samples have Cd contents exceeding the State Food Security Standards (0.2 mg x kg(-1)) with Cd/Zn ratios exceeding the suggested critical threshold of 0.015. Widest variation was found for Cd and smallest for Zn, showing rice Cd prone to environmental stress. The extent to which the contents of the analyzed elements varied with rice areas was rater for Cd and Se than for Zn, though the contents followed in the same order: polluted area > acid paddy area and neutral paddy area. This further evidenced a determinacy of chemical availability in rice Cd uptake. Taking the reference dose values by WHO and USEPA, the health risk by Cd exposure to the rice diet from different areas was estimated. The consumption of rice from polluted area and acid paddy area may impose serious health risks for subsistence diet farmers though those from neutral paddy area may be still safe under the WHO guideline. It is demanded that the problem of the rice rains high in Cd and low in Zn and Se, and serious potential risk should be taken into account while developing high-yielding rice in acid and polluted rice ares of South China. Technology for depressing Cd uptake and low-Cd cultivar breeding should he pursued in rice production sector in the future.