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A MASS BALANCE APPROACH TO DETERMINE ARSENIC ABSORPTION RATES FROM CONTAMINATED WATER BY RICE DURING THE FOOD PREPARATION PROCESS
Ackerman, A H., P A. Gallagher, A N. Parks, C A. Schwegel, J T. Creed, D. T. Heitkemper, AND N. Vela. A MASS BALANCE APPROACH TO DETERMINE ARSENIC ABSORPTION RATES FROM CONTAMINATED WATER BY RICE DURING THE FOOD PREPARATION PROCESS. Presented at 2003 European Winter Conference on Plasma Spectrochemistry, Garmisch-Partenkirchen, Germany, January 12-17, 2003.
There are two objectives for this task:
1.) Development of a preliminary arsenic speciation based database for target foods; and
2). Investigate the feasibility of compositing foods (starches, fruits, etc) in conjunction with a separate task entitled "Speciation of Arsenic in Dietary and Dietary Composite Samples to Provide a More Complete Assessment of Arsenic Exposure from Dietary Sources" which focuses on proteins such as seafoods. Ultimately, this would help to minimize the number of samples needed to develop the database while preserving analytical reliability.
Rice represents a unique set of arsenic exposure assessment challenges in that it does contain a relatively high concentration of arsenic and it does absorb about 100% of its dry weight during food preparation. Arsenic exposure from consumption of rice can conceptually be divided into arsenic native to the rice [As(III), DMA, MMA and As(V)] and arsenic absorbed from the water [As(III) and As(V)] during food preparation. The arsenic exposure associated with the rice is a relative constant while the arsenic absorbed from the water may depend on the concentration of arsenic in the water used in food preparation and the way the rice is cooked (boiled or steamed). The actual exposure becomes difficult to calculate without knowing the native rice arsenic concentration, the arsenic concentration in the water and the percentage of arsenic absorbed during the food preparation process. The ability to estimate the native arsenic concentration in rice using a nearly quantitative extraction process has been reported  and the concentration of arsenic in the water is analytically fairly simple to determine. The unknown quantity is the absorption rates of the arsenic from the water to the rice. Given that rice is a common staple and that the water used for food preparation could represent a large percentage of the exposure dose, it is important to estimate the absorption rates in order to better characterize rice as an arsenic exposure source.
This presentation will use an arsenic mass balance approach throughout the food preparation process in order to estimate arsenic absorption rates from water. Native arsenic concentrations will be determined for the rice, water and cooked rice. These data will be utilized along with percent moisture increase for the cooked rice to calculate the arsenic absorption rates. Total arsenic concentrations and speciation data will be acquired for individual components (rice, water, cooked rice) and the quality of the mass balance for boiled vs steamed rice will be discussed. All results will be based on replicate IC-ICP-MS analysis and the absorption rates will be estimated.