his colleagues analyzed arsenic in 13 different rice cultivars grown in Bangladesh, India, and China. They found as much as a 14-fold The anoxic and reducing enviUptake of arsenic by rice plants difference in grain arsenic among ronment of flooded paddies mocould be stifling crucial micronuthe cultivars. “This hints that it bilizes arsenic, which is readily trients such as selenium in rice could be possible to breed a hightaken up by plants, explains Andy grains, according to new research yield variety that accumulates Meharg, a biogeochemist at the published in ES&T (2009, DOI beneficial micronutrients but not University of Aberdeen (U.K.) and 10.1021/es901825t). The findings arsenic,” Zhu says. Because the coauthor of the new papers. He are bad news for people in Asia, variation in grain arsenic was afand his team analyzed arsenic whose diet is primarily rice, befected by the site where cause selenium helps cultivars were grown, lowcleanse toxic arsenic from arsenic varieties will have to the body. be bred to match regional But a second ES&T study soil types, he adds. demonstrates the potential The lack of a reliable and for breeding rice cultivars convenient way to measure that shun the arsenic comvolatilization of arsenic monly found in flooded from soil has left this part paddies (2009, DOI of the global geochemical 10.1021/es901844q). The pathway a mystery, Meharg pair of studies is capped says. In the third study, he by the first measurements and his team describe a roof arsenic volatilization bust field method for meafrom soil (2009, DOI Arsenic-driven loss of micronutrients in rice creates a suring arsenic volatilization. 10.1021/es9018755), dem- health burden. “This will open up a whole onstrating the benefits of and the trace nutrients selenium, new area of research,” Polya an across-the-board approach to zinc, and nickel in 230 soil and predicts. examining arsenic exposure, plant samples from three districts Based on silver-nitrate-impregsays Enzo Lombi, a biogeochemin Bangladesh. In Bangladesh, nated, silica-gel-filled tubes, the ist at the University of South well water is high in arsenic and method uses chromatography Australia. is used both for irrigating fields equipment found in virtually any Exposure to arsenic, a class 1 and drinking. The researchers chemical analysis lab, Meharg carcinogen for which there is no found that although arsenic levels says. He and his team found that safe dose, affects hundreds of milin the rice grains mimicked pat0.01% of soil arsenic was removed lions of people worldwide, says terns observed for the soil and by volatilization from paddy soils Dave Polya, an environmental water, grain concentrations of the in Bangladesh over three weeks. geochemist at the University of micronutrients did not reflect lev“This offers a method to help esManchester (U.K.). Chronic expoels found in the external environtablish whether volatilization is an sure leads to diseases such as skin ment. Instead, the scientists important part of the global arand bladder cancer. Although documented for the first time that senic budget,” Fendorf says. most research has focused on selenium, zinc, and nickel exhibAs studies of arsenic in rice naturally occurring arsenic in well ited significant declines with rishelp to clarify people’s risk, govwater, new studies hint that food ing arsenic content in the rice. ernments are beginning to act. could be a significant source of “Selenium actively promotes China has set a standard of 150 arsenic, he says. the efflux of arsenic from the huparts per billion inorganic arsenic The arsenic composition of man body,” says Scott Fendorf, a in rice, the U.K. has banned conrice typically ranges from 100 to soil biogeochemist at Stanford sumption of rice milk for children 500 micrograms per kilogram University. “Therefore, arsenic under 4.5 years of age, and the (µg/kg), and many people in could be a double-edged sword if European Food Safety Authority is Asia eat at least 200 g/day of it is depressing selenium in rice.” currently reviewing arsenic in rice, Polya says. “Therefore, the One solution could be to breed rice. levels in rice commonly lead to an arsenic-resistant rice variety, arsenic exposures at or above —JANET PELLEY says Yong-Guan Zhu, an environthe World Health Organization’s mental biologist at the Chinese limit for water of 10 (µg/kg), asAcademy of Sciences and coausuming daily water intake of 2 thor of the second paper. He and kg/day,” he says. JUPITERIMAGES
Arsenic in rice: a recipe for nutrient loss
8004 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / November 1, 2009
10.1021/es902922b
2009 American Chemical Society
Published on Web 10/07/2009
