Reducing total mercury and methylmercury accumulation in rice grains through water management and deliberate selection of rice cultivars.

Rice consumption has been identified as a major route of methylmercury (MeHg) exposure in some areas of inland China. We investigated two potential mitigation methods (water management and deliberate selection of rice cultivars) to reduce the amount of total mercury (Hg) and MeHg within the grain. Rice grown aerobically had markedly reduced total Hg and MeHg concentrations as well as a much lower proportion of MeHg in the grain. Remarkably, there were considerable variations in the total Hg and MeHg concentrations as well as the proportion of MeHg in the grain among the 24 cultivars grown in the same paddy soil. The Hg tolerance index (expressed as % mean of control root growth) also varied substantially among the different cultivars. Furthermore, negative correlations were found between the total Hg and MeHg concentrations (P<0.05) of grain and the proportion of MeHg in the grain (P<0.01).