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Speciation of the Bioaccessible Fraction of Arsenic in Rice using IC-ICP-MS
Citation:
Young, A. R., H. Trenary, P. A. CREED, JOHN T. CREED, C. A. SCHWEGEL, M. Madhavi, J. T. Trent, AND C. Gallawa. Speciation of the Bioaccessible Fraction of Arsenic in Rice using IC-ICP-MS. Presented at 2010 Pittcon, Orlando, FL, February 28 - March 05, 2010.
Impact/Purpose:
Develop analytical approaches to quantify reactive intermediates within the metabolic pathway that biotransforms inorganic arsenic to DMA(V). The ability to quantify these species will enhance the mode of action (within NHEERL) and the bioavailability / bioaccessibility research (within NERL).
Description:
Dietary arsenic exposure occurs mainly through drinking water and food; therefore, both aspects should be incorporated into any aggregate exposure assessment. Drinking water exposures are predominantly inorganic arsenic (AsIng) while dietary exposures are made up of a diverse set of arsenicals with widely varying toxicities. Rice samples collected from different regions of the world have been shown to be high in total arsenic. For this reason, preliminary arsenic speciation based databases for rice are beginning to be published in the peer reviewed literature. These datasets are indicating AsIng and dimethylarsenic acid (DMA) are the predominant arsenicals found in rice; however, the AsIng fraction can be as high as 90% and as low as 10% of the total arsenic present in the sample. Therefore, applying a fixed distribution to existing total arsenic measurements is less than an ideal approach to assessing the exposure. Currently, the species specific rice data are mainly derived from chemically based extractions. These extractions are relatively simple and quantitative, but how well these extractions reflect the biologically relevant component of the exposure is unknown. If an assay could estimate the species specific bioaccessibility of an exposure and capture gastrointestinal (GI) tract based biotransformation, it would improve the arsenic exposure estimate for rice. An application of this type of assay should provide data essential to estimating biologically relevant exposures in rice and other target foods. This presentation will attempt to estimate the bioaccessible fraction associated with U.S. consumed rice using a synthetic GI extraction technique prior to speciation via IC-ICP-MS. The species specific bioaccessible data will then be used to estimate AsIng exposures from rice. This data will then be combined with consumption data from the What We Eat in America (WWEIA) database within a stochastic model to predict exposures. The WWEIA consumption data is derived from surveys conducted between 1999 and 2006. Finally, the potential for biotransformation of the extracted arsenicals will be evaluated by using an in vitro technique in which a GI extracted rice sample is incubated in the cecum content of a mouse.