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Species Specific Bio-accessibility Estimates of Arsenic in US Consumed Rice
Citation:
Mantha, M., J. Trent, E. A. Yeary, R. A. Wilson, C. A. SCHWEGEL, P. A. CREED, K. Kubachka, T. Hanley, N. Shockey, D. Heitkemper, J. Caruso, J. XUE, AND JOHN T. CREED. Species Specific Bio-accessibility Estimates of Arsenic in US Consumed Rice. Presented at Third International Symposium on Metallomics, Munster, GERMANY, June 15 - 18, 2011.
Impact/Purpose:
Develop analytical approaches to quantify reactive intermediates within the metabolic pathway of arsenic to enhance the mode of action / metabolism research (within NHEERL) and to develop the bioavailability / bioaccessibility research (within NERL). By developing species specific bioaccessibility estimates of inorganic arsenic in demographically harvested target foods it becomes possible to estimate population based exposures using probabilistic models like SHEDS.
Description:
Inorganic arsenic (iAs) has been classified as a Class I carcinogen by the International Agency for Research on Cancer (IARC). For non-occupationally exposed individuals, the two predominant exposure routes for arsenic are drinking water and diet. Drinking water exposures contain almost exclusively iAs but dietary sources of exposure contain over 25 arsenicals with widely varying LD50 values. The wide range of toxicity for specific chemical forms of arsenic has caused exposure scientists to adopt speciation approaches to improve dietary risk estimates in target foods. Rice is a target food for speciation analysis because it is widely consumed and has been shown to be high in total arsenic by both crop and market basket-based studies. In some of these studies, rice has been shown to contain iAs, dimethylarsinic acid (DMA), and occasionally monomethylarsonic acid (MMA). These occurrence-based studies are useful in source recognition but are lacking because they do not provide an estimate of the physiologically relevant component of the exposure. To move from occurrence to population-based exposure estimates, the variability of the biologically relevant iAs concentration needs to be estimated for a sample set that reflects the consumption habits of the population. This presentation will discuss the use of an in vitro gastrointestinal extraction protocol to obtain a bioaccessibility estimate for a set of rice grain types (white long grain, white short grain, white medium grain, parboiled and instant rice) that were collected over an eight week period from the US supply chain. The speciation data set will be determined using LC-ICP-MS. The ultimate goal of this study is to combine the distribution of biologically relevant iAs concentration in US consumed rice with the distribution of consumption patterns from What We Eat in America (WWEIA) in a Stochastic Human Exposure and Dose Simulator (SHEDS) model to determine a population-based exposure assessment for the US.