No abstract

Recent studies have clearly showed that rice can be another important pathway of MeHg exposure to inhabitants in higher Hg hotspots, such as Hg mining areas in Guizhou Province, China. However, the elevated Hg levels only account for about 1% of Chinese cultivation area and the majority of rice planting areas are ranked the low Hg areas. Therefore, it is important and necessary to verify MeHg accumulation in rice in low Hg areas because rice is the stable daily food in these extensive areas. Importantly, the human health-risk assessment of Hg exposure doesn't consider the extreme values observed. Although these extreme values are fewer, it may result in critical Hg exposure for local inhabitants and may become the determinants or "drivers" of environmental decisions and policies, even though most individuals are exposed to far lower concentrations and risks. This study clearly confirmed rice has the highest ability to accumulate MeHg not only in Hg mining areas also in low Hg areas. The THg and MeHg concentrations in the rice samples collected from northeast plain rice advantage area were lower than that of Xinyang city, and significantly lower than that of reported from the rice from southern China. However, in extreme micro-environments, routine consumption of rice provides a THg and MeHg intake of 11.6 µg kg -1 and 1.8 µg kg -1 of body weight per day, respectively. The MeHg intake was 18 times of RfD of USEPA and 7.8 times of PTWI by JECFA. It clearly demonstrates that a few inhabitants, such as Gouxi and Dashui in Wanshan, are exposed to Hg and MeHg to a much serious health risk.