Browsing by Author "Deacon, C."
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Item Arsenic limits trace mineral nutrition (Selenium, Zinc, and Nickel) in Bangladesh rice grain(2009) Williams, P.N.; Islam, S.; Islam, R.; Jahiruddin, M.; Adomako, E.E.; Solaiman, A.R.M.; Rahman, G.K.M.M.; Lu, Y.; Deacon, C.; Zhu, Y.-G.; Meharg, A.A.A reconnaissance of 23 paddy fields, from three Bangladesh districts, encompassing a total of 230 soil and rice plant samples was conducted to identify the extent to which trace element characteristics in soils and irrigation waters are reflected by the harvested rice crop. Field sites were located on two soil physiographic units with distinctly different As soil baseline and groundwater concentrations. For arsenic (As), both straw and grain trends closely fitted patterns observed for the soils and water. Grain concentration characteristics for selenium (Se), zinc (Zn), and nickel (Ni), however, were markedly different. Regressions of shoot and grain As against grain Se, Zn, and Ni were highly significant (P< 0.001), exhibiting a pronounced decline in grain trace-nutrient quality with increasing As content. To validate this further, a pot experiment cultivar screening trial, involving commonly cultivated high yielding variety (HYV) rice grown alongside two U.S. rice varieties characterized as being As tolerant and susceptible, was conducted on an As amended uniform soil. Findings from the trial confirmed that As perturbed grain metal(loid) balances, resulting in severe yield reductions in addition to constraining the levels of Se, Zn, and Ni in the grain.Item Enhanced transfer of arsenic to grain for Bangladesh grown rice compared to US and EU(Elsevier, 2010) Adomako, E.; Solaiman, A.R.M.; Williams, P.N.; Deacon, C.; Rahman, G.K.M.M.; Meharg, A.A.A field survey was conducted in arsenic impacted and non-impacted paddies of Bangladesh to assess how arsenic levels in rice (Oryza sativa L.) grain are related to soil and shoot concentrations. Ten field sites from an arsenic contaminated tubewell irrigation region (Faridpur) were compared to 10 field sites from a nonaffected region (Gazipur). Analysis of the overall data set found that both grain and shoot total arsenic concentrations were highly correlated (P<0.001) with soil arsenic. Median arsenic concentrations varied by 14, 10 and 3 fold for soil, shoot and grain respectively comparing the two regions. The reason for the sharp decline in the magnitude of difference between Gazipur and Faridpur for grain arsenic was due to an exponential decline in the grain/shoot arsenic concentration ratio with increasing shoot arsenic concentration. When the Bangladesh data were compared to EU and US soil–shoot–grain transfers, the same generic pattern could be found with the exception that arsenic was more efficiently transferred to grain from soil/shoot in the Bangladesh grown plants. This may reflect climatic or cultivar differences.Item Geographical Variation in Total and Inorganic Arsenic Content of Polished (White) Rice(American Chemical Society, 2009) Meharg, A.A.; Williams, P.N.; Adomako, E.E.; Lawgali, Y.Y.; Deacon, C.; Villada, A.; Cambell, R.C.J.; Sun, G.; Zhu, Y.-G.; Feldmann, J.; Raab, A.; Zhao, F.-J.; Islam, R.; Hossain, S.; Yanai, J.An extensive data set of total arsenic analysis for 901 polished (white) grain samples, originating from 10 countries from 4 continents, was compiled. The samples represented the baseline (i.e., not specifically collected from arsenic contaminated areas), and all were for market sale in major conurbations. Median total arsenic contents of rice varied 7-fold, with Egypt (0.04 mg/kg) and India (0.07 mg/kg) having the lowest arsenic content while the U.S. (0.25 mg/kg) and France (0.28 mg/kg) had the highest content. Global distribution of total arsenic in rice was modeled by weighting each country’s arsenic distribution by that country’s contribution to global production. A subset of 63 samples from Bangladesh, China, India, Italy, and the U.S. was analyzed for arsenic species. The relationship between inorganic arsenic content versus total arsenic content significantly differed among countries, with Bangladesh and India having the steepest slope in linear regression, and the U.S. having the shallowest slope. Using country-specific rice consumption data, daily intake of inorganic arsenic was estimated and the associated internal cancer risk was calculated using the U.S. Environmental Protection Agency (EPA) cancer slope. Median excess internal cancer risks posed by inorganic arsenic ranged 30-fold for the 5 countries examined, being 0.7 per 10,000 for Italians to 22 per 10,000 for Bangladeshis, when a 60 kg person was considered.Item Inorganic arsenic and trace elements in Ghanaian grain staples(Elsevier, 2011) Adomako, E.E.; Williams, P.N.; Deacon, C.; Meharg, A.A.A total of 549 samples of rice, maize, wheat, sorghum and millet were obtained from markets in Ghana, the EU, US and Asia. Analysis of the samples, originating from 21 countries in 5 continents, helped to establish global mean trace element concentrations in grains; thus placing the Ghanaian data within a global context. Ghanaian rice was generally low in potentially toxic elements, but high in essential nutrient elements. Arsenic concentrations in rice from US (0.22 mg/kg) and Thailand (0.15 mg/kg) were higher than in Ghanaian rice (0.11 mg/kg). Percentage inorganic arsenic content of the latter (83%) was, however, higher than for US (42%) and Thai rice (67%). Total arsenic concentration in Ghanaian maize, sorghum and millet samples (0.01 mg/kg) was an order of magnitude lower than in Ghanaian rice, indicating that a shift from rice-centric to multigrain diets could help reduce health risks posed by dietary exposure to inorganic As.Item Inorganic arsenic levels in baby rice are of concern(Elsevier, 2008) Meharg, A.A.; Sun, G.; Williams, P.N.; Adomako, E.E.; Deacon, C.; Zhu, Y.-G.; Feldmann, J.; Raab, A.Inorganic arsenic is a chronic exposure carcinogen. Analysis of UK baby rice revealed a median inorganic arsenic content (n = 17) of 0.11 mg/kg. By plotting inorganic arsenic against total arsenic, it was found that inorganic As concentrations increased linearly up to 0.25 mg/ kg total arsenic, then plateaued at 0.16 mg/kg at higher total arsenic concentrations. Inorganic arsenic intake by babies (4-12 months) was considered with respect to current dietary ingestion regulations. It was found that 35% of the baby rice samples analysed would be illegal for sale in China which has regulatory limit of 0.15 mg/kg inorganic arsenic. EU and US food regulations on arsenic are non-existent. When baby inorganic arsenic intake from rice was considered, median consumption (expressed as mg/kg/d) was higher than drinking water maximum exposures predicted for adults in these regions when water intake was expressed on a bodyweight basis.Item Selenium characterization in the global rice supply chain(American Chemical Society, 2009) Williams, P.N.; Enzo, L.; Sun, G.; Scheckel, K.; Zhu, Y.-G.; Feng, X.; Zhu, J.; Carey, A.-M.; Adomako, E.E.; Lawgali, Y.; Deacon, C.; Meharg, A.A.For up to 1 billion people worldwide, insufficient dietary intake of selenium (Se) is a serious health constraint. Cereals are the dominant Se source for those on low protein diets, as typified by the global malnourished population. With crop Se content constrained largely by underlying geology, regional soil Se variations are often mirrored by their locally grown staples. Despite this, the Se concentrations of much of the world’s rice, the mainstay of so many, is poorly characterized, for both total Se content and Se speciation. In this study, 1092 samples of market sourced polished rice were obtained. The sampled rice encompassed dominant rice producing and exporting countries. Rice from the U.S. and India were found to be the most enriched, while mean average levels were lowest in Egyptian rice: ∼32-fold less than their North American equivalents. By weighting country averages by contribution to either global production or export, modelled baseline values for both were produced. Based on a daily rice consumption of 300 g day-1, around 75% of the grains from the production and export pools would fail to provide 70% of daily recommended Se intakes. Furthermore, Se localization and speciation characterization using X-ray fluorescence (µ-XRF) and X-ray absorption near edge structure (µ-XANES) techniques were investigated in a Se-rich sample. The results revealed that the large majority of Se in the endosperm was present in organic forms.Item Variation in rice cadmium related to human exposure(Environmental Science and Technology, 2013-05) Meharg, A.A.; Norton, G.; Deacon, C.; Williams, P.; Adomako, E.E.; Price, A.; Zhu, Y.; Li, G.; Zhao, F.J.; McGrath, S.; Villada, A.; Sommella, A.; De Silva, P.M.C.S.; Brammer, H.; Dasgupta, T.; Islam, M.R.Cereal grains are the dominant source of cadmium in the human diet, with rice being to the fore. Here we explore the effect of geographic, genetic, and processing (milling) factors on rice grain cadmium and rice consumption rates that lead to dietary variance in cadmium intake. From a survey of 12 countries on four continents, cadmium levels in rice grain were the highest in Bangladesh and Sri Lanka, with both these countries also having high per capita rice intakes. For Bangladesh and Sri Lanka, there was high weekly intake of cadmium from rice, leading to intakes deemed unsafe by international and national regulators. While genetic variance, and to a lesser extent milling, provide strategies for reducing cadmium in rice, caution has to be used, as there is environmental regulation as well as genetic regulation of cadmium accumulation within rice grains. For countries that import rice, grain cadmium can be controlled by where that rice is sourced, but for countries with subsistence rice economies that have high levels of cadmium in rice grain, agronomic and breeding strategies are required to lower grain cadmium. © 2013 American Chemical Society.Item Variations in concentrations of arsenic and other potentially toxic elements in mine and paddy soils and irrigation waters from southern Ghana(Springer, 2010) Adomako, E.; Deacon, C.; Meharg, A.A.This study was undertaken to ascertain the impact of gold mining on soil and water chemistry as well as on rice grain quality. Samples collected from both gold mining and non-gold mining regions of southern Ghana were analysed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of arsenic and other potentially toxic elements (PTEs). Significant differences were observed between sites with respect to soil As, Co, Cu, Pb and Zn concentrations. Paddy soils from the Anum Valley Irrigation Project site, located close to the old Konongo Gold Mine in the Ashanti region, contained up to 103 mg arsenic/kg. Although higher arsenic concentrations were recorded in mine soils from Bogosu in the western region, paddy soil samples from this region contained relatively low concentrations of arsenic, suggesting that the contribution of gold mining to soil contamination is a function of distance from the point source of contaminants. Transfer of soil arsenic to rice grain was significantly higher in gold mining regions compared to non-gold mining regions. At the Anum Valley Irrigation Project site, where surface waters containing 144 μg arsenic/l were used for paddy irrigation, rice grain arsenic concentration reached 0.59 mg/kg, indicating a potential risk of arsenic transfer to the food chain.