Reviews on Inorganic Arsenic in Rice Grains: Assessment of Regional Variation, Health Risk and Mitigation Strategies

Arsenic in rice grains presents a food safety concern, with potential adverse effects to humans. Despite the presence of numerous publications on arsenic in rice grains, arsenic uptake by rice grains, regional variation, health risks and its mitigation strategies need better understanding. In this study, mechanisms of arsenic uptake in rice grains, variation of inorganic arsenic (iAs) in rice grains, and human exposure and risk were investigated for all continents. Human exposure and risk analyses were performed following the probabilistic concept to incorporate uncertainty. Rice plants primarily absorb arsenic through silicon and phosphate transport pathways, with arsenite [As(III)] and arsenate [As(V)] being the predominant forms. The iAs concentrations in rice grains vary significantly around the globe. Several Asian countries, particularly Bangladesh and China, showed elevated iAs concentrations in rice grains, averaging 121 ± 93.5 µg/kg. The highest average of cancer risk was observed in Asia (2.39 × 10⁻⁴), followed by Oceania (8.87 × 10⁻⁵) and South America (8.82 × 10⁻⁵) while Europe exhibited the lowest risk (1.59 × 10⁻⁵). Various mitigation approaches including mineral supplementation, advanced soil amendments, water management practices, biotechnological interventions and genetic modification were investigated. The advanced soil amendments showed significant reduction in iAs accumulation in rice grains (biochar: 30–72% reduction, nanoparticles: up to 90% reduction, layered double hydroxides [LDH]: 69–88% reduction). The genetic modification strategies targeting specific genes (OsHAC1;1, OsHAC1;2, OsABCC1) showed 20–75% reduction in grain arsenic accumulation. Overall, this research presents valuable insights in developing effective strategies to minimize arsenic accumulation in rice grains.