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An Investigation of Bioaccessibility of Arsenic in Rice using IC-ICP-MS
Citation:
Young, A. R., H. Trenary, S. K. Yathavakilla, P. A. CREED, JOHN T. CREED, AND J. XUE. An Investigation of Bioaccessibility of Arsenic in Rice using IC-ICP-MS. Presented at 2009 Pittcon , Chicago, IL, March 08 - 13, 2009.
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:
Arsenic exposure occurs mainly through drinking water and food; therefore, both aspects should be incorporated into any aggregate exposure assessment. Drinking water exposures are predominately inorganic arsenic while dietary exposures are made up of a diverse set of arsenicals with widely varying toxicities. Rice collected throughout the world has been shown to be relatively high in total arsenic. In fact, the FDA’s market basket survey supports this observation and for this reason rice is a target food group for dietary speciation studies. Arsenic speciation has been conducted on rice grown in endemic areas and in the U.S. In these studies, inorganic arsenic and DMA are the predominant arsenicals found in rice; however, the variation associated with the distribution of these two arsenicals is far from a constant. Therefore, a quantitative exposure assessment for rice needs to incorporate not only species specific information, but also the variation associated with the distribution of the arsenicals, in order to improve the exposure risk estimate for rice. Another factor which needs to be considered in the exposure assessment is the biologically relevant arsenic dose associated with rice consumption. Information on bioaccessible arsenic, the fraction of analyte which is solubilized by the gastrointestinal (GI) tract, could provide a means to estimating the biologically relevant dose. Ideally, this bioaccessibility term would also include the GI tract induced biotransformations associated with the ingested arsenicals. Currently, the species specific rice data are mainly comprised of chemically based extractions. These extractions are relatively simple and quantitative, but it is not known how accurately these extractions correlate with bioaccessibility. Therefore, an assay that can estimate the species specific bioaccessibility and capture the biotransformation in the GI tract should improve the exposure estimate. An application of this type of assay should provide data essential to estimating biologically relevant exposures in target foods. This presentation will attempt to estimate the bioaccessible fraction associated with U.S. consumed rice using a synthetic gastrointestinal extraction technique prior to speciation via ICICP-MS. Finally, the potential for biotransformation of the extracted arsenicals will be evaluated by using an in vitro technique in which a gastrointestinally extracted rice sample is incubated in the cecum content of a mouse.