Overview
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.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |