Abstract

Rice productivity and grain quality are threatened by the dual challenges of arsenic (As) and
other toxic metals contamination and climate change. This study presents the impacts of elevated
CO2 (eCO2), eO3, and eTemp on trace and toxic elements transformation (for As), mobilization
and accumulation in paddy soils and rice. Future climate scenarios promote soil bio-geochemical
shifts that enhance microbes mediated bio-transformations of As by methylation and thiolation,
thereby increasing its mobility. Simultaneously, climate change combined with As toxicity
disrupts rice physiology, altering As uptake, translocation, and accumulation patterns.
Consequently, rice grains show elevated total and inorganic As, coupled with a depletion of
essential nutrients such as iron, zinc, and key sugar metabolites. Among the toxic metals; Cd
showed significant increase across all rice tissues under elevated climatic factors. Whereas,
accumulation of Cr and Pb generally declined, with exception to Cr in grain this increased under
eCO2. In general, elevated climatic conditions reduced trace nutrient concentrations in grains,
except for Se, which increased by ~32% under eTemp, and Mo increased by ~6% under eO3. The
effects of elevated climatic factors were more pronounced (>30% reduction) for Fe, Co, Se, Mo,
and Ni, than Mn, Cu, and Zn (~10% reduction). The rice grown in high As containing soil leads
to major imbalances in organic acids, phytosterols, and fatty acids in grains, resulting in yield
reductions of up to 40%. These effects are projected to exacerbate hidden hunger and increase
cancer risks across several Asian countries by 2050 with ~700 cases per 100,000 individuals.
Overall, these findings demonstrated that elevated climatic factors can substantially alter the
accumulation and interaction patterns of trace and toxic elements in rice grains, posing potential
risks to grain quality and food safety under future climate change scenarios.