Xie et al. 2026 — Co-occurrence of selenium and toxic elements in Chinese selenium-enriched rice
Xie and colleagues measured arsenic (tAs) and cadmium (Cd) alongside selenium (Se) in 54 commercial selenium-enriched rice samples sourced from 14 provinces across China, finding that the premium nutritional positioning of Se-enriched rice does not preclude co-contamination with toxic elements. Arithmetic mean concentrations were 0.11 mg/kg (110 ppb) for total As and 0.08 mg/kg (80 ppb) for Cd, measured by HDXRF spectrometry. A Monte Carlo-based health risk assessment found overall risk from As and Cd intake via Se-enriched rice to be within acceptable bounds under average consumption, but highlighted that Se bioaccessibility (median 7.0 µg/kg, overall 14.6 ± 8.7%) varied substantially by region, with southern China showing the highest bioaccessible Se (29.0 µg/kg). The study is notable for combining speciation-naive total-element analysis with in vitro digestion (PBET model) for Se, without speciation of As into inorganic and organic fractions.
Key numbers
- n = 54 commercial Se-enriched rice samples, 14 provinces (northeast, northwest, southwest, south, central, and east China)
- Total As, arithmetic mean: 0.11 mg/kg (110 ppb), wet weight (assumed polished rice, dry-weight basis not specified; Shapiro-Wilk normality confirmed, p > 0.05)
- Total Cd, arithmetic mean: 0.08 mg/kg (80 ppb)
- Se total concentration: regional variation reported; highest in southern China
- Bioaccessible Se (PBET model), median: 7.0 µg/kg; highest region (northeast) mean: 20.0 ± 9.9%; lowest region (eastern) mean: 8.4 ± 4.7%
- As speciation: not performed; values are total arsenic only
- Chinese national standard for Cd in rice: 0.2 mg/kg (GB 2762-2017); Codex standard: 0.4 mg/kg
- Spatial distribution mapped using ArcGIS 10.0
Methods (brief)
HDXRF (high-definition X-ray fluorescence) spectrometry for total As and Cd in rice grain. Se bioaccessibility assessed by PBET in vitro digestion. Statistical analysis in SPSS 21.0 and Origin 2022; normal distribution confirmed for As, Cd, and Se by Shapiro-Wilk; Kruskal-Wallis H used for bioaccessible Se (non-normal). LOD/LOQ not stated in extracted text. Note: As values are total arsenic; the study does not speciate inorganic from organic arsenic, making direct comparison to iAs-specific regulatory thresholds (e.g., EU Reg. 2023/915 for rice) inappropriate without a conversion factor.
Implications
Certification: Se-enriched rice is a niche but growing product category marketed as nutritionally enhanced; the co-occurrence of tAs at 110 ppb mean and Cd at 80 ppb means that Se fortification does not create a clean-metal profile. These concentrations are below Chinese regulatory caps but at levels relevant to HMT&C threshold discussion for rice-based products.
Courses: Useful case study for explaining that nutritional fortification does not eliminate heavy metal risk; the “health halo” of selenium-enriched products needs qualification.
App: tAs 110 ppb mean and Cd 80 ppb mean for commercial selenium-enriched polished rice from China. Note: total As, not iAs; app risk scoring for iAs should apply a conservative fraction (typically 0.5–0.7 for polished white rice from Asia without speciation data).