Alimohammadi et al. 2018 — Heavy metals in Tehran supermarket vegetables across two seasons

The authors measured seven heavy metal(oid)s (As, Cd, Cr, Cu, Ni, Pb, Zn) in six common Tehran supermarket vegetables — cucumber and tomato (fruit vegetables), lettuce and cabbage (leafy vegetables), potato and carrot (root vegetables) — across two seasons (summer and autumn 2016), then computed target hazard quotients (THQ), total THQ (TTHQ), and excess lifetime cancer risk (ELCR) for Tehran adult consumers. Lead exceeded Codex limits in multiple vegetable–season cells (potato, cabbage, carrot, tomato), chromium exceeded reference limits in root and leafy vegetables, and the calculated total cancer risk from As + Cd + Pb exposure was 2.26 × 10⁻⁴ — unsafe even under non-conservative assumptions.

Key numbers

• Sample design: six vegetables × 16 samples each = 96 samples total. Sampling months were August and September 2016 (summer) and October and November 2016 (autumn). Three collection trips per season. Samples sourced from Tehran’s central fruit and vegetable market.
• Sample prep: 200 g washed, air-dried, ground, oven-dried at 105 °C for 24 h; 500 mg dry digested with 10 mL concentrated HNO₃ on a hot plate; filtered through Whatman No. 42; diluted to 25 mL with deionized water (Methods §2.1).
• Detection limits (ng/L in digestate): As 1.0, Cd 2.5, Cr 4.4, Zn 2.0, Cu 0.8, Ni 2.8. Recovery 90–105 % on a reference plant material; three calibration standards inserted every ten samples; all samples in triplicate (Methods §2.2).
• Mean concentrations in summer (mg/kg fresh weight; bold = exceeds Codex/reference standard cited in source) — Table 4:
  • Cucumber: As 0.007, Cd 0.001, Cr 0.127, Cu 0.062, Ni 0.119, Pb 0.040, Zn 0.912.
  • Tomato: As 0.011, Cd 0.009, Cr 0.234, Cu 0.186, Ni 0.161, Pb 0.079, Zn 1.612.
  • Lettuce: As 0.001, Cd 0.005, Cr 0.279, Cu 0.196, Ni 0.203, Pb 0.123, Zn 1.938.
  • Cabbage: As 0.003, Cd 0.005, Cr 0.679, Cu 0.237, Ni 0.570, Pb 0.311, Zn 3.271.
  • Potato: As 0.005, Cd 0.005, Cr 0.952, Cu 0.745, Ni 0.622, Pb 0.454, Zn 4.434.
  • Carrot: As 0.003, Cd 0.003, Cr 0.678, Cu 0.462, Ni 0.462, Pb 0.307, Zn 3.860.
• Mean concentrations in autumn (mg/kg fresh weight; bold = exceeds standard) — Table 5:
  • Cucumber: As 0.001, Cd 0.005, Cr 0.222, Cu 0.186, Ni 0.148, Pb 0.098, Zn 1.343.
  • Tomato: As 0.002, Cd 0.015, Cr 0.412, Cu 0.359, Ni 0.232, Pb 0.241, Zn 2.064.
  • Lettuce: As 0.001, Cd 0.001, Cr 0.318, Cu 0.231, Ni 0.326, Pb 0.136, Zn 1.819.
  • Cabbage: As 0.003, Cd 0.003, Cr 0.708, Cu 0.306, Ni 0.639, Pb 0.304, Zn 3.541.
  • Potato: As 0.005, Cd 0.005, Cr 1.104, Cu 0.714, Ni 2.115, Pb 0.472, Zn 4.578.
  • Carrot: As 0.003, Cd 0.003, Cr 0.640, Cu 0.367, Ni 0.371, Pb 0.282, Zn 2.410.
• Codex / reference standard limits (mg/kg fresh weight) used by authors: Pb 0.1 (most vegetables) and 0.3 (lettuce, cabbage); Cd 0.05–0.2 depending on vegetable; Cr 0.5 (0.2 for lettuce); Cu 10; Ni 1.5–2; Zn 20; As 0.1 (Islam et al. 2016) (Tables 4, 5 footnotes).
• Summer Pb exceedances: cabbage 1.03×, potato 4.5×, carrot 3.0× Codex limit. Summer Cr exceedances: cabbage 1.35×, potato 1.9×, carrot 1.35× limit (Results §3.1).
• Autumn exceedances: Pb in tomato 2.4×, cabbage 1.04×, potato 4.7×, carrot 2.8×; Cr in cabbage 1.4×, carrot 1.2×, potato 1.4× (Results §3.1). Ni in potato (2.115 mg/kg) exceeded the 1.5 mg/kg reference (autumn Table 5).
• Across all vegetables and both seasons, mean metal ordering was Zn > Cr > Ni > Cu > Pb > Cd > As (Results §3.1). Mean concentrations by vegetable group decreased root > leafy > fruit; the authors note this sequence is also reported by Paltseva et al. 2018 (New Jersey) and Gorospe 2012 (San Francisco).
• Daily vegetable intakes in Tehran (kg/person/day): cucumber 0.020, tomato 0.052, lettuce 0.028, cabbage 0.0054, potato 0.059, carrot 0.0052 (Dali Bandarian zadeh 2005; cited at §3.3.1).
• Health-risk parameters: body weight 70 kg, exposure frequency 350 days/year, exposure duration 70 years, default bioavailability 1.0 for As and Cd and 0.6 for Pb (Methods §2.3, §2.4).
• Oral reference doses (mg/kg-day) and cancer slope factors (Table 2): As RfD 0.0003 CSF 1.5; Cd RfD 0.001 CSF 6.3; Pb RfD 0.00035 CSF 0.0085 (Bamuwamye 2015); Cr RfD 1.5; Cu RfD 0.04; Ni RfD 0.02; Zn RfD 0.3.
• ADD, HQ, ELCR results (Table 7):
  • As: ADD 2.0256 × 10⁻⁵ mg/kg-day; HQ 0.0675; ELCR 3.04 × 10⁻⁵.
  • Cd: ADD 2.9500 × 10⁻⁵; HQ 0.0295; ELCR 1.86 × 10⁻⁴.
  • Pb: ADD 1.2006 × 10⁻³; HQ 0.300; ELCR 6.12 × 10⁻⁶.
  • Cr: ADD 2.6047 × 10⁻³; HQ 1.76 × 10⁻³ (ELCR not computed — authors note Cr(III)/metallic Cr not classified as carcinogenic and Cr(VI) presence in vegetables is unlikely per Robson 2003).
  • Cu: ADD 1.8985 × 10⁻³; HQ 0.0475.
  • Ni: ADD 2.9136 × 10⁻³; HQ 0.146.
  • Zn: ADD 1.2911 × 10⁻²; HQ 0.0430.
• TTHQ = 0.63 (HQ < 1 for every metal; total well below 1). Cumulative cancer risk for As + Cd + Pb = 2.26 × 10⁻⁴ — exceeds the USEPA 10⁻⁴ acceptable upper bound even under non-conservative bioavailability. With Pb default 0.6 bioavailability applied, As + Cd + Pb cancer risk = 2.22 × 10⁻⁴ — still unsafe (Results §3.3, Conclusions).
• Statistical analysis: Kruskal–Wallis test with R 3.3.2 after Fligner-Killeen homogeneity test, α = 0.05 (Methods §2.2). Significant seasonal differences (Table 6): cucumber (autumn higher for Cd, Pb, Cr, Cu, Zn; summer higher for As), tomato (autumn higher for Pb, Cr, Ni, Cu; summer higher for As), lettuce (autumn higher for Pb, Cr, Cu), cabbage (autumn higher for Cr, Cu), potato (no significant seasonal differences), carrot (summer higher for Ni, Cu, Zn).

Methods (brief)

Six vegetable types (Lactuca sativa, Brassica oleracea var. capitata, Solanum lycopersicum, Cucumis sativus, Solanum tuberosum, Daucus carota subsp. sativus) at n = 16 each were collected over four months (August–November 2016) from Tehran’s central fruit and vegetable market — the sole supplier of supermarkets in Tehran — across three collection trips per season. Samples (200 g per replicate) were washed, separated, air-dried, ground in a mixer, then oven-dried at 105 °C for 24 h to obtain dry weight. 500 mg dry sample was digested with 10 mL concentrated HNO₃ on a hot plate, filtered (Whatman No. 42), and diluted to 25 mL in deionized water. Total elemental concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn were measured by ICP-OES (Spectro ARCOS-ICP-OES) using a multi-element standard calibration curve, with detection limits in the 0.8–4.4 ng/L digestate range and recovery 90–105 % on a reference plant material. Three calibration standards were inserted every ten samples and all samples were analyzed in triplicate. Concentrations were reported on dry-weight basis and converted to fresh-weight using gravimetric moisture content (Table 1; 81.7–96.4 %). Statistical analyses used the non-parametric Kruskal–Wallis test (after Fligner-Killeen homogeneity testing) in R 3.3.2 at α = 0.05. No speciation was performed: As is reported as total elemental arsenic and Cr as total chromium. Carcinogenic risk for As, Cd, Pb used the LADD × CSF formulation with USEPA default bioavailability (1.0 for As/Cd, 0.6 for Pb). Non-carcinogenic risk used ADD ÷ RfD and was summed across metals to compute TTHQ.

Implications

• Certification (HMTc): Adds Iranian retail-market occurrence rows for tAs, Cd, Cr, Cu, Ni, Pb, and Zn across six common vegetables, with seasonal sub-strata. Particularly informative for Pb on root and leafy vegetables (multiple ×3–5 Codex exceedances) and Cr on the same. The Cr column is total chromium per the source’s own framing — not Cr(VI) — and should not be pooled with Cr(VI) evidence.
• Courses: Suitable case study for two methodology points relevant to brand QA and supply-chain audiences: (1) how seasonal sourcing geography affects market-basket metal loads even within a single municipality, and (2) why Pb and Cr drive cancer-risk and exceedance signals on root vegetables while As/Cd remain low in the same matrix.
• App: Contributes occurrence data points to cucumber, tomato, lettuce, cabbage, potatoes, and carrot for Pb, Cd, tAs, Cr, Cu, Ni, and Zn on fresh-weight basis.

Wiki pages this source may touch

• vegetables
• leafy-vegetables
• root-vegetables
• non-root-vegetables
• cucumber
• tomato
• lettuce
• cabbage
• potatoes
• carrot
• arsenic-total
• cadmium
• chromium
• copper
• nickel
• lead
• zinc
• eu-1881-2006-contaminants-superseded
• codex-cadmium-mls

Verification notes

• Identity checks (DOI, raw_handle, cite-key surname/year) returned no existing wiki page; this is a fresh ingest.
• Speciation: As reported by authors as total elemental arsenic (no iAs/tAs split), so this page routes As as tAs. Cr reported as total chromium, with explicit acknowledgement in §2.4 that Cr(VI) presence in vegetables is unlikely (Robson 2003) and ELCR was not computed for Cr; routed as Cr (total), not chromium-hexavalent.
• Paper-internal anomaly noted but does not block ingest: Table 3 (max/min/SD of metals, mg/kg) reports values for Cr, Cu, Ni, Pb, Zn that are inconsistent with the per-vegetable per-season means in Tables 4 and 5 — e.g., Table 3 lists Cr max as 0.151 mg/kg while Tables 4–5 report Cr means up to 1.104 mg/kg (potato, autumn). The SDs in Table 3 (e.g., Cr 0.312, Ni 0.799, Zn 1.233) are consistent with Tables 4–5 spreads, so the SD row appears correct while Max/Min appear typeset incorrectly. Tables 4 and 5 are used as the primary numeric anchor for this page; Table 3 is not relied on.
• Brand firewall: no brands were named in the source. Methods names the instrument vendor (Spectro ARCOS-ICP-OES) and reagent supplier (Merck, Frankfurt) — preserved under the Exception 2 scientific-reproducibility carve-out.
• Wiki/HMTc firewall: no synthesis claims, no HMTc threshold proposals, no consumer advisory language carried over from the source.
• products: [] is intentional. This is raw fresh produce (not packaged formats); no product-page slug applies. Routing-malformed advisory for the missing products array is expected and does not indicate a defect.
• Slug choices: paper categorizes tomato and cucumber as “fruits” (botanically fruit vegetables); routed via non-root-vegetables umbrella plus the specific tomato and cucumber slugs. Potato routed as potatoes (plural form is the canonical ingredient slug).
• Audit subagent (2026-06-01) flagged [[ingredients/non-root-vegetables]] as an invented slug not in the taxonomy snapshot — verified against docs/gpt-collaboration/taxonomy-snapshot.md line 40 and wiki/ingredients/non-root-vegetables.md; both confirm the slug exists. False positive; no change applied.
• Audit subagent (2026-06-01) recommended rewording the “consistent with Paltseva 2018 and Gorospe 2012 patterns reported elsewhere” parenthetical for unambiguous attribution; reworded to make clear the comparison is the source’s own framing (PDF p. 4 §3.1) and not a wiki-side cross-source synthesis.
• Audit subagent (2026-06-01) noted that the Ni-in-potato autumn 2.115 mg/kg exceedance call is faithful to Table 5 (bolded cell, 1.5 mg/kg parenthetical limit) but is the wiki’s inference from the table rather than direct §3.1 prose. Acceptable as-is per subagent; no change applied.

Page history

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