Arsenic accumulation and speciation in rice grains influenced by arsenic phytotoxicity and rice genotypes grown in arsenic-elevated paddy soils.

Rice consumption is a major route of As exposure to human for the population of worldwide. This study investigates the effect of phytotoxicity and rice genotypes on the content and speciation of As in rice grains grown in different levels of As-elevated paddy soils from Taiwan. Three levels of As-elevated soils and six rice genotypes commonly planted in Taiwan were used for this study. The results indicate that As contents in grains of rice is not proportional to soil As concentrations and they were equal or higher in indica genotypes than japonica genotypes used in this study. It was also found that the As phytotoxicity not only reducing the grain yields but also the As concentrations in grain of rice. The predominant As species found in rice grains were dimethylarsinic acid (DMA) and arsenite. The concentrations of DMA increased with total As concentrations, wherggeas the arsenite remained in a narrow range from 0.1 to 0.3 mg kg(-1). Because of the lower toxicity of DMA than inorganic As species, the health risks may not be increased through consumption of rice even when total As content in the grains is increased.