Tayeb and Movassaghghazani 2025 — Lead and cadmium in olive and corn oils, northern Iran
This study measured lead and cadmium in 60 commercial and traditional olive and corn oil samples from Gonbad-Kavus City in northern Iran using graphite furnace atomic absorption spectrometry (GFAAS) after microwave digestion. All samples had quantifiable Pb and Cd levels; all Pb concentrations were below the 80 µg/kg ISIRI (Iranian national) limit. Hazard Index (HI) values were below 1 for all oils, indicating no non-carcinogenic risk. However, the Margin of Exposure (MOE) for lead in traditional olive oil was below 10,000, signaling a concern for potential carcinogenic risk in that specific product type.
Key numbers
Lead concentrations (µg/kg wet weight, mean ± SD):
- Traditional corn oil: 32.40 ± 6.13 (min 24.90, max 42.40)
- Commercial corn oil: 19.27 ± 8.12 (min 9.60, max 37.00)
- Traditional olive oil: 17.48 ± 4.82 (min 7.90, max 18.70)
- Commercial olive oil: 13.27 ± 3.37 (min 7.90, max 18.70)
Cadmium concentrations (µg/kg wet weight, mean ± SD):
- Traditional corn oil: 5.77 ± 1.34 (min 3.80, max 7.75)
- Commercial corn oil: 4.48 ± 1.80 (min 2.44, max 7.40)
- Commercial olive oil: 4.14 ± 0.53 (min 2.86, max 5.30)
- Traditional olive oil: 3.50 ± 0.72 (min 2.60, max 4.66)
All Pb values below ISIRI MRL of 80 µg/kg and EU limit of 100 µg/kg (Regulation EU 2023/915). No MRL exists for Cd in vegetable oils under Iranian or EU standards.
Risk assessment (70 kg adult, daily consumption 0.147 g corn oil + 0.328 g olive oil):
- HI (Pb + Cd combined): all oils < 1 (no non-carcinogenic risk)
- MOE for Pb: traditional olive oil = 7,875 (below 10,000 threshold, concern flagged); all other oils > 10,000 (no significant carcinogenic concern)
- MOE for Cd: all oils ≥ 36,000 (no concern)
- EFSA BMDL10 values used: Pb 0.63 µg/kg bw/day, Cd 0.36 µg/kg bw/day
Traditional corn oil showed significantly higher Pb than all other types (p < 0.001). Authors attribute higher lead in traditional oils to environmental contamination and absence of industrial refining steps.
Methods
GFAAS (Varian SpectrAA-200 with GTA-110 graphite tube atomizer, deuterium background correction). Microwave digestion: 1 g sample + 6 mL HNO3 (65%) + 2 mL H2O2 (30%); 32 min total at staged wattages (500→800→1000→1300 W). Wavelengths: Pb 283.3 nm, Cd 228.8 nm. Chemical modifier: NH4H2PO4/Mg(NO3)2. Three replicates per sample. Aqueous working standards 10–60 µg/L. Statistical analysis: SPSS v24, ANOVA, Duncan’s multiple comparison test. Non-cancer risk: HQ = EDI/RfD (RfD Cd = 1 µg/kg bw; RfD Pb = 3.75 µg/kg bw). Cancer risk: MOE method per EFSA.
Implications
Certification: Pb levels in these northern Iranian oils (13–32 µg/kg) are well below Codex/EU limits (100 µg/kg) and ISIRI (80 µg/kg). Cd levels (3.5–5.8 µg/kg) are low and below any regulatory threshold. Traditional (unrefined) oils showed consistently higher Pb than commercial oils, suggesting refining reduces Pb burden. This paper provides directly usable ppb-level data for olive oil and corn oil Pb/Cd profiling.
Courses: Demonstrates that traditional/artisanal oils sourced from local stores may carry higher metal loads than commercially refined equivalents, with practical implications for supply-chain sourcing decisions.
App: Directly usable for olive-oil and corn-oil contamination profiles for Pb and Cd. Traditional corn oil Pb (mean 32.4 µg/kg = 32.4 ppb) is the highest value in this dataset.