Zafarzadeh & Shahryari 2025 — Heavy metals in Sari rice, north Iran
This study assessed Pb, Cd, Cu, and Zn contamination in commercially sold rice from Sari (Mazandaran Province, northern Iran), a major national rice-production hub. All 144 samples exceeded the Iranian/international Pb safety limit of 0.2 mg/kg; the Pb non-carcinogenic hazard quotient (HQ > 1) indicated significant risk for both children and adults. Spatial analysis identified a coastal Pb hotspot in northern Sari near the Caspian Sea (up to 9.88 mg/kg) versus much lower concentrations in southern areas (0.38 mg/kg), attributable to tourism-related activities and wastewater irrigation.
Key numbers
Mean ± SD concentrations in rice (mg/kg):
- Pb: 2.77 ± 2.14 mg/kg (2,770 ± 2,140 ppb) — ALL 144 samples exceeded 0.2 mg/kg limit
- Cd: < 0.0001 mg/kg (below detection limit)
- Cu: 3.95 ± 2.11 mg/kg
- Zn: 11.73 ± 5.62 mg/kg
Spatial Pb range: 0.38 mg/kg (southern Sari) to 9.88 mg/kg (northern coastal region near Caspian Sea)
Risk assessment:
- HQ (Pb) > 1 for both adults and children: significant non-carcinogenic risk
- Other metals: acceptable carcinogenic and non-carcinogenic risk levels
- ILCR (total cancer risk) for Pb: exceeds acceptable range
Method: Metrohm 797 VA Computrace polarographic trace analyzer (stripping voltammetry).
Contamination patterns by direction:
- North (coastal): Pb hotspot — highway traffic, tourism, wastewater irrigation
- East: Zn/Cu elevation — fertilizer use
- Urban centers: multiple metals
Methods (brief)
Polarographic trace analysis using Metrohm 797 VA Computrace (stripping voltammetry), not ICP-MS. Three brands (H, Sh, B), each 48 samples from 16 mills. Samples collected June–September 2022. Risk assessment used HQ, ILCR, and THQ methodology per US EPA/Iran EPA standards; reference doses per national and international guidelines. ADI approach also applied. Spatial mapping performed across four cardinal directions of Sari city.
Implications
Certification: This is a striking finding — 100% exceedance of Pb limits in 144 commercial rice samples from a major Iranian rice production region. Mean Pb of 2,770 ppb is approximately 14-fold above the 200 ppb Codex limit for polished rice (Codex Stan 193). This study is strong evidence for geographic source variability as a major driver of rice Pb contamination. Iranian rice origin should be a flag in supply chain sourcing.
Courses: Excellent case study on spatial variation of heavy metals in rice; the coastal/inland gradient driven by Caspian Sea proximity and tourism-related wastewater illustrates anthropogenic contamination mechanisms clearly.
App: Geographic breakdown directly relevant to the app’s risk-by-origin model. Rice from northern Iran (Mazandaran) would carry a high-Pb flag in sourcing assessment.
Microbiome: Not addressed.