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 critical review synthesizes evidence on cadmium pollution in rice and wheat across China’s rice–wheat cropping systems, integrating literature from January 2000 to June 2022 with bibliometric mapping to identify contamination patterns, health-risk metrics, uptake/transport mechanisms, and research hotspots. The authors compile reported cadmium (Cd) concentrations in rice and wheat grains across key producing provinces in the Yangtze River Basin and the southeastern Yellow River Basin, then translate these levels into exposure indicators (average daily intake and hazard quotient) to highlight where dietary Cd risk is most elevated. The paper also reviews how soil properties (especially pH and organic matter), agronomic inputs (notably phosphate fertilizers), and industrial sources (mining, smelting, wastewater irrigation, and e-waste activities) influence Cd entry into farmland and ultimately into grains. Mechanistically, it summarizes rice and wheat pathways for Cd movement from soil to roots, shoots, and grain, emphasizing transporter-mediated steps and “rate-limiting” barriers (roots and nodes in rice; root-to-shoot and xylem–phloem transfer in wheat) that can be targeted for risk reduction relevant to a heavy metal certification program.
Who was reviewed
Rather than enrolling human or animal participants, this review evaluates published studies and monitoring datasets from rice and wheat production landscapes, with an emphasis on provinces where rice–wheat systems are common (e.g., Sichuan/Chongqing through the Yangtze River Basin to Jiangsu/Zhejiang and into Shandong/Henan). The “who” in scope therefore includes (1) crop populations (rice and wheat cultivars and genotypes) grown under variable soil chemistries and management, (2) farmland soils affected by both geogenic background and anthropogenic inputs, and (3) exposed consumer populations inferred through dietary intake modeling (children 2–6 years, adolescents 7–17 years, and adults ≥18 years) using established intake-rate and body-weight references. The paper’s risk framing is explicitly food-chain oriented: Cd accumulates in edible grain, then contributes to human exposure largely through staple consumption patterns, making the evidence directly applicable to certification claims that depend on geographic sourcing, lot-level variability, and crop- and soil-specific drivers of Cd uptake.
Most important findings
Across the reviewed literature, cadmium pollution in rice and wheat is unevenly distributed, with the Yangtze River Basin (notably Hunan) repeatedly identified as a high-risk zone where grain Cd levels and non-carcinogenic risk indicators are elevated above recommended limits and HQ thresholds.
| Critical point | Details |
|---|---|
| Grain Cd frequently exceeds food-safety limits in key regions | Reported mean Cd ranges span 0.007–1.45 mg/kg in rice and 0.008–2.0 mg/kg in wheat, with exceedance patterns clustered in parts of Sichuan/Chongqing, Hunan, and the Yangtze River Delta. |
| Hunan stands out for elevated concentrations and drivers | The review attributes Hunan’s higher Cd burdens to mining/smelting, phosphate fertilizer inputs, sewage irrigation, and electronics/e-waste activities, with paddy-soil Cd in several Xiangjiang River Basin cities reported well above recommended levels. |
| Dietary risk (HQ) often exceeds 1, especially for wheat | Using an oral RfD of 1 µg/kg body weight/day, the review reports average HQ values of ~1.20 (rice) and ~1.54 (wheat), indicating non-carcinogenic concern where local grain consumption and grain Cd are both high. |
| Regional averages exceed recommended limits by large margins | The authors report that average Cd concentration exceeded the recommended limit by ~62% for rice and ~81% for wheat, highlighting routine compliance challenges in contaminated sourcing zones. |
| Mechanistic control points suggest testable interventions | In rice, uptake/partitioning involves transporters such as OsIRT1/OsNramp1 (root uptake), OsHMA3 (root vacuolar sequestration), OsHMA2 (delivery to tissues), and OsLCT1 (phloem transport), with xylem loading and phloem unloading described as key rate-limiting steps; in wheat, Cd uptake is primarily root-mediated and grain Cd depends strongly on root–shoot transfer and xylem–phloem redistribution. |
Key implications
For HMTC, cadmium pollution in rice and wheat supports tighter region- and supplier-specific controls: primary regulatory impacts center on enforcing grain Cd limits aligned to food standards and on documenting upstream contamination sources; certification requirements should mandate lot-based grain testing plus contextual soil-risk screening (pH, SOM, and known mining/fertilizer pressures) to reduce false assurance. Industry applications include sourcing away from high-HQ provinces, adopting low-Cd cultivars, and implementing agronomic mitigation (pH management, organic matter strategies, and input auditing for phosphate fertilizers). Research gaps persist in translating transporter/genotype insights into scalable procurement specs and in real-time monitoring; practical recommendations include supplier mapping, trigger-based intensified testing in hotspots, and remediation verification before certification claims.
Citation
Gao Y, Duan Z, Zhang L, Sun D, Li X. The Status and Research Progress of Cadmium Pollution in Rice- (Oryza sativa L.) and Wheat- (Triticum aestivum L.) Cropping Systems in China: A Critical Review. Toxics. 2022;10(12):794. doi:10.3390/toxics10120794
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.
