Bioavailability of arsenic from rice: significance of rice genotypes

Shofiqul Islam a, b, c, M. M. Rahman b, c, L. Duan b, c, M.R. Islam a and R. Naidu b, c

a Department of Soil Science, Bangladesh Agricultural University, Bangladesh

b Global Centre for Environmental Remediation (GCER), University of Newcastle, Australia

c Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Australia

shofiqul.islam@uon.edu.au

Bioaccumulation of arsenic in rice grain from paddy soils and contaminated- irrigation water poses a significant health risk to humans. Inorganic arsenic is classified as a human carcinogen and chronic exposure of this can cause fatal damage to kidney, brain, heart, bladder and lungs of millions of people who rely on rice as a staple food. Therefore, assessing the bioavailability of arsenic from rice is crucial for understanding human exposure and to reduce the risk of arsenic-related diseases. In this study, an in vivo assay using swine was used to measure the bioavailability of arsenic from cooked rice of twelve genotypes grown in arsenic-contaminated field sites in Bangladesh. The average arsenic concentrations in each rice genotypes ranged from 108 ± 4 µg/kg to 580 ± 6 µg/kg. The speciation results indicate that inorganic arsenic contents varied from 73 to 99% depending on the varieties. In swine assay, different swine groups were administered with different arsenic species orally, by intravenous i.e. injection and fed cooked rice and finally blood arsenic levels were analyzed by ICP-MS (Agilent technologies) immediately after collection and arsenic bioavailability from rice was calculated by pharmacokinetic analysis. This study demonstrates that rice genotypic characters influenced arsenic bioavailability in rice grain grown in arsenic-contaminated areas and the bioavailability varied between 25% and 94%. Results indicate that arsenic in salt tolerant rice genotypes Binadhan-10 (25%) as well as brown rice genotypes Kheali Boro (35%) and Local Boro (40%) has lower bioavailability compared to other rice genotypes. Most commonly cultivated and consumed variety (BRRI dhan28) has arsenic bioavailability of 70%, which pose significant risk to consumers. Calculation of maximum tolerable daily intake based on bioavailable portion from rice was higher than those calculated based on inorganic and organic arsenic concentration. Thus, arsenic bioavailability from rice is cultivar dependent and can vary due to chemical form of arsenic. So, both genotypic characters and speciation plays an important role in arsenic bioavailability from rice.

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