A new study out of China shows that for millions of people at risk of eating toxic amounts of mercury-laced food, fish isn’t the problem. Rice is.
Background:Mercury, once released into the environment can be methylated by bacteria to produce methylmercury, a potent neurotoxicant. Methylmercury poisoning has been linked with diminishing the IQ of children exposed in the womb and with raising blood pressure and other heart-disease risks among adults. Methylmercury is bioaccumulated especially in the marine food-chain. Because of the high concentrations resulting from the bioaccumulation, fish consumption is considered the primary pathway of methylmercury (MeHg) exposure for most people in the world. However, in the inland regions of China, most of the residents eat little fish, but they live in areas where a significant amount of mercury (Hg) is present in the environment.
The new study:To investigate salient MeHg exposure for the general adult population in Inland China, Zhang and his colleagues selected four locations within Guizhou Province representing typical rural areas, where the diet is primarily locally grown agricultural products: Wanshan (Hg mining and smelting activities), Qingzhen (coal-fired power plant), Weining (artisanal zinc smelting activities), and Leigong Natural Reserve (no direct Hg contamination sources).
Methylmercury and total mercury exposure through drinking water, diet, and respiration were assessed for adults in the four regions by performing mercury speciation analsis. Previous sampling provided data for air, water, fish, meat, and poultry, while agricultural products (rice, corn, and vegetables), drinking water from Wanshan and Leigong, and total gaseous mercury in Wanshan were newly evaluated in this study. These data were collectively used to calculate probable daily intakes for the general adult population.
Although mercury exposures for these communities varied dramatically, in every one of them “rice accounted for 94 to 96 percent of the probable daily intake of methylmercury”. Guizhou’s heavy cereal contamination traces in large part, the study says, to the fact that rice paddies harbor the types of bacteria that can convert inorganic mercury to its more toxic, methylated form. The probable daily intake (PDI) of MeHg was considerably higher in people living in Wanshan than in the other areas; approximately 34% of Wanshan residents exceeded the reference dose for MeHg established by the U.S. Environmental Protection Agency. The MeHg PDI in the other three locations were all below the reference dose.
The new study
Hua Zhang, Xinbin Feng, Thorjørn Larssen, Guangle Qiu, Rolf D. Vogt,
In Inland China, Rice, Rather than Fish, Is the Major Pathway for Methylmercury Exposure, Environ Health Perspect, 118 (2010) 1183-1188.
doi:10.1289/ehp.1001915
Related studies Ping Li, Xinbin Feng, Guangle Qiu,
Methylmercury Exposure and Health Effects from Rice and Fish Consumption: A Review, Int. J. Environ. Res. Public Health, 7/6 (2010) 2666–2691.
doi: 10.3390/ijerph7062666
Hua Zhang, Xinbin Feng, Thorjørn Larssen, Lihai Shang, Ping Li,
Bioaccumulation of Methylmercury versus Inorganic Mercury in Rice (Oryza sativa L.) Grain, Environ. Sci. Technol., 2010, 44/12 (2010) 4499–4504.
DOI: 10.1021/es903565t Lu Lia, Feiyue Wang, Bo Meng, Marcos Lemes, Xinbin Feng, Guibin Jiang,
Speciation of methylmercury in rice grown from a mercury mining area, Environmental Pollution, 158/10 (2010) 3103-3107.
doi:10.1016/j.envpol.2010.06.028 Bo Meng, Xinbin Feng, Guangle Qiu, Yong Cai, Dingyong Wang, Ping Li, Lihai Shang, Jonas Sommar,
Distribution Patterns of Inorganic Mercury and Methylmercury in Tissues of Rice (Oryza sativa L.) Plants and Possible Bioaccumulation Pathways, J. Agric. Food Chem., 58/8 (2010) 4951–4958.
DOI: 10.1021/jf904557x Lisamarie Windham-Myers, Mark Marvin-Dipasquale, David P. Krabbenhoft, Jennifer L. Agee, Marisa H. Cox, Pilar Heredia-Middleton, Carolyn Coates, Evangelos Kakouros,
Experimental removal of wetland emergent vegetation leads to decreased methylmercury production in surface sediment, J. Geophys. Res., 114 (2009) G00C05.
doi:10.1029/2008JG000815 Xinbin Feng, Ping Li, Guangle Qiu, Shaofeng Wang, Guanghui Li, Lihai Shang, Bo Meng, Hongmei Jiang, Weiyang Bai, Zhonggen Li, Xuewu Fu,
Human Exposure To Methylmercury through Rice Intake in Mercury Mining Areas, Guizhou Province, China, Environ. Sci. Technol., 2008, 42/1 (2008) 326–332.
DOI: 10.1021/es071948x Liang-Yen Lin, Lan-Fang Chang, Shiuh-Jen Jiang,
Speciation Analysis of Mercury in Cereals by Liquid Chromatography Chemical Vapor Generation Inductively Coupled Plasma-Mass Spectrometry, J. Agric. Food Chem., 56/16 (2008) 6868–6872.
DOI: 10.1021/jf801241w Guangle Qiu, Xinbin Feng, Ping Li, Shaofeng Wang, Guanghui Li, Lihai Shang, Xuewu Fu,
Methylmercury Accumulation in Rice (Oryza sativa L.) Grown at Abandoned Mercury Mines in Guizhou, China, J. Agric. Food Chem., 56/7 (2008) 2465–2468.
DOI: 10.1021/jf073391a Jian-Bo Shi, Li-Na Liang, Gui-Bin Jiang,
Simultaneous Determination of Methylmercury and Ethylmercury in Rice by Capillary Gas Chromatography Coupled On-line with Atomic Fluorescence Spectrometry, J. AOAC International, 88/2 (2005) 665-669.
doi: 10.5555/jaoi.2005.88.2.665 Milena Horvat, Natasa Nolde, Vesna Fajon, Vesna Jereb, Martina Logar, Sonja Lojen, Radojko Jacimovic, Ingrid Falnoga, Qu Liya, Jadran Faganeli, Damjana Drobne,
Total mercury, methylmercury and selenium in mercury polluted areas in the province Guizhou, China, Sci. Total Environ., 304 (2003) 231–256.
doi:10.1016/S0048-9697(02)00572-7 
Related EVISA Resources Link Database: Uses of mercury compounds Link database: Toxicity of Organic mercury compounds Brief summary: Speciation and Toxicity Link Database: Human exposure to methylmercury via the diet
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their fish consumption because of methylmercury content last time modified: September 15, 2010
