Shavali-gilani et al. 2025 — Heavy metals in canned tomato paste, olives, and pickled cucumbers, Iran
This Iranian study surveyed eight metals (Cd, Cu, As, Fe, Pb, Zn, Hg, Sn) in 49 samples of canned pickled cucumbers, tomato paste, and olives collected from Tehran markets, using AAS-flame and graphite furnace for most analytes and ICP-MS for mercury and tin. All three product types contained detectable lead at average concentrations above the Codex Alimentarius permissible limit of 0.10 mg/kg for canned products; mercury was not detected in any sample. Tin was detected in all canned goods, with tomato paste showing the highest Sn level (0.41 mg/kg), but all values remained far below the EU maximum of 200 mg/kg and Codex 150–250 mg/kg. The study highlights lead as the key canning-associated contaminant in these products.
Key numbers
All concentrations in mg/kg wet weight (as consumed). ND = not detected.
| Metal | Canned pickled cucumbers | Canned tomato paste | Canned olives | Codex limit |
|---|---|---|---|---|
| Pb | 0.22 ± 0.08 | 0.19 ± 0.07 | 0.19 ± 0.04 | 0.10 mg/kg (canned products) |
| Cd | ND | 0.008 ± 0.005 | 0.005 ± 0.001 | 0.05 mg/kg (fruiting vegetables) |
| As | ND | 0.0005 ± 0.0004 | ND | — |
| Fe | ND | 0.48 ± 0.4 | ND | — |
| Sn | 0.11 ± 0.05 | 0.41 ± 0.21 (reported as 0.4 ± 0.2 in table) | 0.32 ± 0.17 | 200 mg/kg (EU); 150–250 mg/kg (Codex) |
| Zn | ND | 0.0071 ± 0.007 | ND | — |
| Hg | ND | ND | ND | — |
| Cu | ND | 0.16 ± 0.1 | ND | — |
Key findings:
- Lead exceeded the Codex limit (0.10 mg/kg) in all three product types; no statistically significant difference in lead levels among the three products (Kruskal-Wallis, P > 0.05).
- Cadmium was significantly higher in tomato paste than in olives and pickles (P < 0.05), but below the Codex fruiting-vegetable limit of 0.05 mg/kg.
- Sn was detected in all products; concentrations are well below regulatory maxima but confirm migration from tinplate cans. Sn species (inorganic vs organotin) were not determined; the ICP-MS method measures total Sn.
- Mercury was not detected in any sample (LOD 0.5 µg/kg, LOQ 1.8 µg/kg).
- Pickled cucumber: only Pb and Sn were detected; Cd, Cu, As, Fe, Zn, Hg all below LOD.
Method LOD/LOQ (ICP-MS): Hg LOD 0.5 µg/kg, LOQ 1.8 µg/kg; Sn LOD 1.4 µg/kg, LOQ 4.6 µg/kg. Method LOD/LOQ (GFAAS): Cd LOD 0.09 µg/kg, LOQ 0.3 µg/kg; As LOD 0.8 µg/kg, LOQ 3.0 µg/kg; Pb LOD 0.7 µg/kg, LOQ 2.3 µg/kg.
Methods (brief)
49 samples from 5 most popular brands at Tehran stores. Sample homogenized, then 1 g digested in 50 mL H2O2 (30%)/HNO3 (65%) 1:1 v/v on hot plate until clear; filtered through 0.45 µm; 170 µL phosphoric acid added. Cu, Fe, Zn by flame AAS; Cd, As, Pb by graphite furnace AAS (GFAAS, Shimadzu AA-6300); Hg and Sn by ICP-MS (Agilent 7500-Ce). All analyses in triplicate. Recovery rates: Cd 93.8%, As 97.3%, Pb 92.7%, Hg 95.0%, Sn 99.2%. Speciation not performed; Hg reported as total Hg (tHg); Sn reported as total Sn (inorganic Sn assumed by context but organotin species not excluded). No speciation of arsenic; the As values therefore represent total As (tAs), not inorganic arsenic (iAs).
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Implications
Certification: Lead consistently above the Codex 0.10 mg/kg canned-product limit in all three Iranian product types is relevant to import screening and product-category certification criteria. The Sn levels, while far below regulatory maxima, confirm tinplate migration even in low-acid products like olives and pickled cucumbers. Total Sn values for these matrices provide baseline reference for HMT&C Sn analyte coverage in canned vegetable categories.
Courses: Illustrates the packaging-source contamination pathway: Pb and Sn contamination is attributable primarily to can construction, not raw ingredient quality. The absence of Hg in any sample (despite previous Iranian studies finding Hg in pickled cucumbers) reflects wastewater irrigation source variation.
App: For risk scoring of canned tomato paste, olives, and pickled cucumbers: Pb is the primary concern; Sn levels are currently well below actionable limits; Hg is not a material concern in these matrices based on this dataset.