Rice genotype's responses to arsenic stress and cancer risk: The effects of integrated birnessite-modified rice hull biochar-water management applications

The health risks associated with ingestion of arsenic (As) via consumption of rice are a global concern. This study investigated the effects of integrated biochar (BC)-water management approaches to As stress and to associated health risks in rice. Rice cultivars, Jayanthi and Ishikari, were grown, irrigated with As-containing water (1 mg L⁻¹), under the following treatments: (1) birnessite-modified rice hull biochar (Mn-RBC)-flooded water management, (2) Mn-RBC-intermittent water management, (3) conventional flooded water management, and (4) intermittent water management. Rice yield in both rice varieties increased by 10%–34% under Mn-RBC-flooded and Mn-RBC-intermittent treatments compared to the conventional flooded treatment. In most cases, inorganic As concentration in rice roots, shoots, husks, and unpolished grains in both rice varieties was significantly (p ≤ 0.05) lowered by 20%–81%, 6%–81%, 30%–75%, and 18%–44%, respectively, under Mn-RBC-flooded, Mn-RBC-intermittent, and intermittent treatments over flooded treatment. Incremental lifetime cancer risks associated with consumption of both rice varieties were also lowered from 18% to 44% under Mn-RBC-flooded, Mn-RBC-intermittent, and intermittent treatments compared to flooded treatment. Overall, the integrated Mn-RBC-intermittent approach can be applied to As-endemic areas to produce safer rice grains and reduce the incremental lifetime cancer risk through rice consumption.