Arsenic Speciation in Australian-Grown and Imported Rice on Sale in Australia: Implications for Human Health Risk

M. Azizur Rahman, Mohammad Mahmudur Rahman, Suzie M. Reichman, Richard P. Lim, Ravi Naidu

Rice is an important route of arsenic (As) exposure to human, especially the populations with rice-based diets. Human health risk of As varies greatly with rice variety and country of origin. The purpose of the present study was to determine total and speciated As in Australian grown and imported rice on sale in Australia to assess their health risk to the consumers. The total As (tAs) concentrations in Australian grown organic brown, medium grain brown, and organic white rice were 438±23, 287±03 and 283±18 µg kg-1 dry weight (d. wt.), respectively. In Bangladeshi, Indian, Pakistani, and Thai rice imported and on sale in Australia, tAs concentrations were 56±05, 92±10, 82±06 and 172±24 µg kg-1, respectively. Asian rice contained mainly inorganic As (iAs; 86-99%), while 18-26% of the tAs in Australian grown rice was dimethylarsinic acid (DMA). Relatively higher concentration of tAs in Australian grown rice than imported rice of Asian origin suggests that Australian rice may be a health risk for the consumers. It was estimated that Australian grown organic brown rice can contribute up to 98% of the FAO/WHO recommended maximum tolerable daily intake limit of iAs (2.1 µg kg-1 body wt. day-1) for Asian immigrants. However, other Australian consumers including the European immigrants unlikely to have health risk of As from rice diets due to their lower rice consumption rates than the Asian immigrants. The risk assessment showed that imported rice on sale in Australia was likely to pose lower health risk to consumers than Australian grown rice.