Arsenic contents, speciation and bioaccessibility in rice grains from China: Regional and variety differences.

As the staple food for Asian countries and with its ability in arsenic accumulation, rice consumption becomes a dominant pathway for As exposure to humans. Here, we collected 108 rice samples from local markets and online sources in 13 major rice-producing regions in China, and determined As contents, speciation and bioaccessibility in the samples. Total As contents were 25-327 μg kg (averaging 120), showing regional differences, with Hunan province being greater than other provinces at 180 vs 110. In rice grains, inorganic As was the dominant species, being 39.9-88.5 (61.1 %), but all being within the Chinese standard at 200 μg kg. Based on the modified physiologically-based extraction test (MPEBT), arsenic bioaccessibility in rice samples was 20.1-82.2 (52.3 %) in the gastric phase and 47.2-113 (81.2 %) in the intestinal phase. Strong positive correlation between total As and bioaccessible As suggested bioaccessible As was content-dependent. Based on the intestinal phase, the rice samples from northern region had lower As bioaccessibility than other regions (59.2 vs 83.2 %), and Japonica variety had lower As bioaccessibility than Indica variety (71.1 vs 83.1 %). This study suggests that rice from markets in China is safe, with their As contents and bioaccessibility showing regional and variety differences.