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Rice is the leading staple food for more than half of the world's population, and approximately 160 million hectares of agricultural area worldwide are under rice cultivation. Therefore, it is essential to fulfil the global demand for rice while maintaining food safety. Rice acts as a sink for potentially toxic metals such as arsenic (As), selenium (Se), cadmium (Cd), lead (Pb), zinc (Zn), manganese (Mn), nickel (Ni), and chromium (Cr) in paddy soil-rice systems due to the natural and anthropogenic sources of these metals that have developed in the last few decades. This review summarizes the sources and basic chemical behaviours of these trace elements in the soil system and their contamination status, uptake, translocation, and accumulation mechanisms in paddy soil-rice systems in major rice-growing countries. Several human health threats are significantly associated with these toxic and potentially toxic metals not only due to their presence in the environment (i.e., the soil, water, and air) but also due to the uptake and translocation of these metals via different transporters. Elevated concentrations of these metals are toxic to plants, animals, and even humans that consume them regularly, and the uniform deposition of metals causes a severe risk of bioaccumulation. Furthermore, the contamination of rice in the global rice trade makes this a critical problem of worldwide concern. Therefore, the global consumption of contaminated rice causes severe human health effects that require rapid action. Finally, this review also summarizes the available management/remediation measures and future research directions for addressing this critical issue.

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Arsenic (As) is toxic for humans, animals, and plants, whereas selenium (Se) is considered as an essential trace element and can cause toxicity during episodic elevated exposure.Interaction between As and Se is a critical factor for a detailed systematic understanding of the transportation, environmental fate, and associated toxicological effects of these metalloids in biological systems. Arsenic and Se induce cytotoxicity and genotoxicity through the generation of reactive oxidation species (ROS). Compared to arsenite (As III ), the methylated arsenicals, including methylarsonous acid (MAs III ) and dimethylarsinous acids (DMAs III ) exhibit more cytotoxic and genotoxic potentials to inhibit more potent enzymes and activate AP˗1 protein, which is a critical marker for genetic stability.Methylated As III and associated metabolites are well-known potential carcinogens that induce toxicity by blocking Se metabolism pathway. Low concentrations of Se compounds under reducing conditions inhibit the DNA repairing process and constraint the binding of zinc finger protein to DNA and ultimately cause the release of zinc from the motif of the zinc finger. Imbalance of Se compounds can lead to the generation of ROS, which can inhibit or decrease genomic stability. Arsenic and Se nexus also affect cellular signaling through activation of the transcription factors such as NFҡB and AP-1. In a nutshell, this review highlights As and Se sources in the environment, their uptake in soil-plant system, interactions between these metals and associated toxicity in major biological compartments, which may assist in addressing the hazardous impacts associated with As and Se contamination. Last but not the lease, this review also summarizes the available remedial measures and future research directions to cope with this critical issue.

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