Comment on "Growing rice aerobically markedly decreases arsenic accumulation".

In a detailed study conducted with potted plants in a greenhouse, Xu et al. (1) recently showed that reducing conditions in soil water maintained by flooding are a significant factor contributing to the uptake of As by rice plants. This is an important issue relevant to human health because a portion of the As taken up by the rice plant is transferred to the rice grain and eventually eaten. We do not dispute the main finding that aerobic cultivation, by reducing the release of As to soil water, can lower the uptake of As by the plant and the incorporation of As in the rice grain. We are compelled to point out, however, that the scale of transfer of As from soil to soil water as well as the transfer from soil water to rice grains observed during this greenhouse study with a nonrice soil differ significantly from observations conducted in cultivated rice paddies in Bangladesh. Such discrepancies warrant further study and suggest that more emphasis should be placed on controlled field studies in current efforts to reduce the uptake of As by rice.