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China: Inorganic Arsenic in Rice - An Underestimated Health Threat ?

(19.05.2010)


Background:
Inorganic arsenic is a confirmed human carcinogen causing skin and bladder cancer. The most common route of exposure is via ingestion of contaminated drinking water or food such as rice. The UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) (an independent scientific committee that provides advice to the Food Standards Agency) has concluded that people should consume as little of this form of arsenic as reasonably. Worldwide concerns over inorganic arsenic in potable water have prompted much research and policy development focusing on removing this chronic human carcinogen. However, recent studies have indicated that elevated inorganic arsenic in rice may additionally contribute significantly to dietary intake. Rice is generally grown under flooded conditions and accumulates As from the soil and water where As mobility is high. The transfer rate of As from soil to grain is an order of magnitude greater in rice than that in wheat or barley, leading to baseline levels of As in rice that are approximately 10-fold higher than those in other cereal grains.


The new study:
A Chinese research group now investigated the health risks for the Chinese population. Twenty-two rice samples from 13 provinces of China were analyzed for their arsenic content. Total arsenic content was determined by ICP-QMS after microwave-assisted digestion. Total As concentration ranged 65.3-274.2 ng g-1, with an average value of 114.4 ng g-1.

Arsenic speciation analysis was performed by using HPLC-ICPMS together with an anion exchange column. 0.2 mol/l trifluoroacetic acid (TFA) was used for the extraction of arsenic from milled rice powder. Four arsenic species, including arsenite (As(III)), arsenate (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA), were detected in most rice samples. The Asi (As(III) + As(V)) species was predominant, accounting for approximately 72% of the total As in rice, with a mean concentration of 82.0 ng g-1.

While the average arsenic concentration in Chinese rice was lower than for some other countries such as Thailand, Bangladesh, Japan, Spain, USA, France and Italy, rice does significantly contribute to human arsenic exposure due to its role as a staple food in China.  
Assuming a consumption rate of 550 g per day of dry weight of rice for Chinese people, the average daily intake of Asi though rice is 45.1 µg per day based on the average value of Asi in rice in our result, which is 37.6 % of the MTDI and about 25 times higher than the value for drinking water.

The authors conclude that rice is the primary source of arsenic in China and may even have been underestimated, since only a few areas with a predominant seafood diet were considered up to now.


The New Study

Feng Liang, Yulan Li, Guilin Zhang, Mingguang Tan, Jun Lin, Wei Liu,  Yan Li, Wenwei Lu, Total and speciated arsenic levels in rice from China, Food Additives & Contaminants: Part A, 27/6 (2010) 810 - 816. doi: 10.1080/19440041003636661  


Related Studies (on arsenic speciation in rice)

Euan Smith, Ivan Kempson, Albert L. Juhasz, John Weber, William M. Skinner, Markus Gräfe, Localization and speciation of arsenic  and trace elements in rice tissues, Chemosphere, 76/4 (2009) 529-535. doi:10.1016/j.chemosphere.2009.03.010

Andrew A. Meharg, Paul N. Williams, Eureka Adomako, Youssef Y. Lawgali, Claire Deacon, Antia Villada, Robert C. J. Cambell, Guoxin Sun, Yong-Guan Zhu, Jörg Feldmann, Andrea Raab, Fang-Jie Zhao, Rafiqul Islam, Shahid Hossain, Junta Yanai, Geographical Variation in Total and Inorganic Arsenic Content of Polished (White) Rice, Environ. Sci. Technol., 43/5 (2009) 1612–1617. DOI: 10.1021/es802612

Andrea Raab, Christina Baskaran, Joerg Feldmann and Andrew A. Meharg, Cooking rice in a high water to rice ratio reduces inorganic arsenic content, J. Environ. Monit., 11 (2009) 41-44, DOI: 10.1039/b816906c

Guo-Xin Sun, Paul N. Williams, Anne-Marie Carey, Yong-Guan Zhu, Claire Deacon, Andrea Raab, Joerg Feldmann, Rafiqul M. Islam, Andrew A. Meharg, Inorganic Arsenic in Rice Bran and Its Products Are an Order of Magnitude Higher than in Bulk Grain, Environ. Sci. Technol., 2008, 42/19 (2008) 7542–7546. DOI: 10.1021/es801238p

Yong-Guan Zhu, Paul N. Williams, Andrew A. Meharg, Exposure to inorganic arsenic from rice: A global health issue?, Environmental Pollution, 154/2 (2008) 169-171. doi:10.1016/j.envpol.2008.03.015

Silvia Torres-Escribano, Mariana Leal, Dinoraz Vélez, Rosa Montoro, Total and Inorganic Arsenic Concentrations in Rice Sold in Spain, Effect of Cooking, and Risk Assessments, Environ. Sci. Technol., 42/10 (2008) 3867–3872. DOI: 10.1021/es071516m

Yamily J. Zavala, Russell Gerads, Hakan Gürleyük, John M. Duxbury, Arsenic in Rice: II. Arsenic Speciation in USA Grain and Implications for Human Health, Environ. Sci. Technol., 42/10 (2008) 3861–3866. DOI: 10.1021/es702748q

Andrew A. Meharg, Guoxin Sun, Paul N. Williams, Eureka Adomako, Claire Deacon, Yong-Guan Zhu, Jörg Feldmann, Andrea Raab, Inorganic arsenic levels in baby rice are of concern, Environmental Pollution, 152/3 (2008) 746-749. doi:10.1016/j.envpol.2008.01.043

Andrew A. Meharg, Enzo Lombi, Paul N. Williams, Kirk G. Scheckel, Jörg Feldmann, Andrea Raab, Yongguan Zhu, Rafiql Islam, Speciation and Localization of Arsenic in White and Brown Rice Grains, Environ. Sci. Technol., 42/4 (2008) 1051–1057. DOI: 10.1021/es702212p

Albert L. Juhasz, Euan Smith, John Weber, Matthew Rees, Allan Rofe, Tim Kuchel, Lloyd Sansom, Ravi Naidu, In Vivo Assessment of Arsenic Bioavailability in Rice and Its Significance for Human Health Risk Assessment, Environ. Health Perspect., 114 (2006) 1826-1831. doi:10.1289/ehp.9322

José Moisés Laparra,  Dinoraz Vélez,  Reyes Barberá,  Rosaura Farré, Rosa Montoro, Bioavailability of Inorganic Arsenic in Cooked Rice:  Practical Aspects for Human Health Risk Assessments, J. Agric. Food Chem., 53/22 (2005) 8829–8833. DOI: 10.1021/jf051365b

P. N. Williams, A.H. Price, A. Raab, S.A. Hossain, Jörg Feldmann, A.A. Meharg, Variation in Arsenic Speciation and Concentration in Paddy Rice Related to Dietary Exposure, Environ. Sci. Technol., 39/15 (2005) 5531–5540. DOI: 10.1021/es0502324



Related EVISA Resources

EVISA brief summary: ICP-MS: A versatile detection system for speciation analysis
 EVISA brief summary: LC-ICP-MS: The most often used hyphenated system for speciation analysis
 EVISA Link database: Toxicity of arsenic species
EVISA Brief summary: Speciation and Toxicity




Related news

EVISA News, March 9, 2010: CEN calls for the development of standardised methods for the analysis of metal species in food
EVISA News, February 23, 2010: US EPA opens inorganic arsenic cancer assessment for public review
EVISA News, December 4, 2009: EFSA: Scientific Opinion on Arsenic in Food
EVISA News, January 31, 2009: Using the right recipe for cooking rice reduces toxic inorganic arsenic content
EVISA News, July 18, 2008: Experts detail how rice absorbs arsenic from the soil
EVISA News, February 15, 2008: Arsenic speciation in rice: a question of the rice plant species
EVISA News, March 7, 2007: Elevated Arsenic Levels Found In Rice Grown In South Central States of the USA
EVISA News, August 3, 2005: Surprisingly high concentrations of toxic arsenic species found in U.S. rice  


last time modified: May 24, 2010



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