Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was reviewed?
This comprehensive review examined the accumulation of arsenic and cadmium in rice and explored current mitigation strategies, with a focus on implications for food safety and heavy metal certification programs. The review synthesized recent findings on the biogeochemical processes controlling arsenic (As) and cadmium (Cd) bioavailability in paddy soils, the molecular mechanisms of uptake, translocation, and detoxification in rice plants, and practical approaches for reducing their concentrations in rice grain. Particular emphasis was placed on similarities and differences between As and Cd dynamics, the impact of soil and water management, genetic factors, and the challenges of simultaneously reducing both elements in rice. The review also identified significant knowledge gaps in environmental, genetic, and management aspects that affect As and Cd accumulation in rice.
Who was reviewed?
The review encompassed a wide array of original research and global data, including field and laboratory studies, large-scale surveys, and genetic investigations. Populations consuming rice as a staple food—especially in Asia—were a primary focus due to their heightened risk of exposure. The reviewed body of work included studies on various rice cultivars, paddy soil types, and environmental conditions across multiple continents, with detailed data from China, Bangladesh, Japan, and other high rice-consuming regions. Research also covered diverse management practices, genetic lines, and geographical variations in rice grain As and Cd content, representing both the scientific and regulatory communities concerned with food safety and heavy metal exposure.
Most important findings
| Critical Points | Details |
|---|---|
| As and Cd transfer from soil to rice grain | Both elements have high potential for transfer, but Cd transfer ratios are one to two orders of magnitude higher than As. Rice is a major dietary source of both elements for many populations. |
| Impact of soil conditions and water management | Flooding decreases Cd but increases As in grain; draining has the opposite effect. Soil pH is a major driver for Cd, while redox potential is more influential for As. |
| Genotype and environmental interactions | Grain As and Cd concentrations vary by up to three orders of magnitude, influenced by rice genotype and growing conditions. Genetic variation in key transporter genes (e.g., OsHMA3, OsNRAMP5 for Cd; Lsi1/Lsi2 for As) explains significant differences in accumulation. |
| Mechanisms of uptake and translocation | As(III) enters via silicon transporters, Cd via Mn transporters. Detoxification involves complexation with phytochelatins and vacuolar sequestration, governed by specific genes. |
| Mitigation strategies | Two main approaches: reduce bioavailability in soil (e.g., liming, Fe/Mn amendments, water management) or decrease plant uptake/translocation (genetic selection, breeding, gene editing). |
| Simultaneous mitigation challenge | Opposing responses to water management and soil amendments complicate efforts to reduce both As and Cd together. |
| Health and regulatory insights | Current international maximum limits for Cd in rice may not sufficiently protect populations with high rice consumption. Inorganic As is a class I carcinogen, and rice can contribute more to As intake than water in some regions. |
| Knowledge gaps | Lack of reliable soil tests for risk prediction, unknown causal genes for many QTLs, and insufficient understanding of gene-environment interactions limit progress in risk management. |
Key implications
For heavy metal certification programs, this review highlights the crucial need to account for both environmental and genetic factors influencing As and Cd in rice grain. Certification standards should reflect regional dietary exposure, genotype-specific accumulation, and the complex interplay between water management and soil chemistry. Simultaneous reduction of As and Cd remains highly challenging, requiring tailored, multi-pronged mitigation strategies. The findings underscore that current regulatory limits may not be stringent enough for high rice-consuming populations, and that certification programs should advocate for improved risk assessment, environmental monitoring, and the deployment of low-accumulating rice cultivars where feasible.
Citation
Zhao F-J, Wang P. Arsenic and cadmium accumulation in rice and mitigation strategies. Plant Soil. 2020;446:1–21. https://doi.org/10.1007/s11104-019-04374-6
Arsenic is a naturally occurring metalloid that ranks first on the ATSDR toxic substances list. Inorganic arsenic contaminates water, rice and consumer products, and exposure is linked to cardiovascular disease, cognitive deficits, low birth weight and cancer. HMTC’s stringent certification applies ALARA principles to protect vulnerable populations.
Cadmium is a persistent heavy metal that accumulates in kidneys and bones. Dietary sources include cereals, cocoa, shellfish and vegetables, while smokers and industrial workers receive higher exposures. Studies link cadmium to kidney dysfunction, bone fractures and cancer.
Heavy metals are high-density elements that accumulate in the body and environment, disrupting biological processes. Lead, cadmium, arsenic, mercury, nickel, tin, aluminum, and chromium are of greatest concern due to persistence, bioaccumulation, and health risks, making them central to the HMTC program’s safety standards.
