Concentration and Risk Assessment of Potentially Toxic Elements, Lead and Cadmium, in Vegetables and Cereals Consumed in Western Iran

Overview

This Iranian market-basket survey quantifies total lead (Pb) and total cadmium (Cd) in eight commodities — potato, onion, tomato, lettuce, leek, carrot, wheat, and rice — purchased from local markets, supermarkets, and grocery stores in Hamadan province, western Iran, between August 2017 and February 2018. Fifty composites per commodity (n=400 total) were microwave-digested in HNO₃/H₂O₂ and quantified by graphite-furnace atomic absorption spectrometry (Thermo Scientific CE 3300) at 217 nm (Pb) and 228.8 nm (Cd). All eight commodity means for both Pb and Cd were below the EU 1881/2006 maximum allowable concentrations (MAC) cited by the authors, but Pb exceeded the MAC in 4 % of carrot samples, 10 % of wheat samples, and 8 % of rice samples; no Cd sample in any commodity exceeded the EU MAC. Adult (70 kg, single-cohort) exposure assessment used Iranian per-capita consumption (68 g/d potato; 39 g/d onion, leek, carrot; 109 g/d tomato; 58 g/d lettuce; 322 g/d wheat; 322 g/d rice from Table 4) and yielded total Cd EDI 0.49 µg/kg bw/day (below JECFA PTDI ≈ 0.8 µg/kg bw/day), all per-commodity Cd THQ values < 1, and all per-commodity Pb MOE values > 1 (range 2.12 wheat / 2.69 rice / 42.86 potato / 133.33 onion), supporting the authors’ conclusion of no significant non-carcinogenic health risk from Pb and Cd exposure through these eight commodities for the adult population.

Key numbers

Method validation (Table 1, p. 103)

Spike recoveries (three spiking levels 0.025, 0.25, 0.5 µg/g): 95.14–106.98 %. RSD < 2 %.

Moisture content (% w/w, oven 105 °C to constant weight)

Potato 74.34; onion 89.20; tomato 94.27; lettuce 93.28; leek 90.48; carrot 86.35; wheat 11.22; rice 13.04.

Table 2 — Lead concentration in eight commodities (n=50 per commodity)

Parenthetical letters (A–D) within a column denote Duncan’s test significant-difference groups (P < 0.05); columns share their own letter alphabet.

Table 3 — Cadmium concentration in eight commodities (n=50 per commodity)

Table 4 — Adult exposure and non-carcinogenic risk (70 kg adult; per-capita consumption from ISIRI 2010 No. 12968)

Total Cd EDI sum across all eight commodities = 0.490 µg/kg bw/day (text §“Risk assessment” p. 105), below the JECFA PTDI of 0.8 µg/kg bw/day derived from the PTMI of 25 µg/kg bw/month.

Risk-assessment parameters (§“Health risk assessment”, p. 102; §“Risk assessment”, p. 105)

• Body weight (single adult cohort): 70 kg.
• RfD Cd: 1 µg/kg bw/day (USEPA, oral chronic).
• JECFA Cd PTMI: 25 µg/kg bw per month (≈ 0.8 µg/kg bw/day PTDI).
• JECFA Pb: PTWI withdrawn; dietary intake of 1.2 µg Pb/kg bw/day cited as the comparator that “would only raise adult blood pressure by 1 mm mercury (Hg),” with MOE = 1.2 / EDI; MOE > 1 → risk negligible.
• THQ formula (Eq. 2): THQ = EDI / RfD.
• TTHQ (Eq. 3): TTHQ = Σ THQ across commodities.
• MOE formula (Eq. 4): MOE = 1.2 (µg/kg bw/day) / EDI Pb.
• EU 1881/2006 MAC values cited by the authors (Tables 2–3): Pb 0.10 mg/kg ww for potato, onion, tomato, carrot; 0.30 mg/kg ww for lettuce and leek; 0.20 mg/kg ww for wheat and rice. Cd 0.10 mg/kg ww for potato, onion, tomato, carrot; 0.20 mg/kg ww for lettuce, leek, wheat, and rice.

EDI rank-order statements

The text (p. 105) states two decreasing rank-orders that are inconsistent with the EDI columns of Table 4 as published:

• Pb (text): wheat > rice > lettuce > leek > carrot > potato > onion > tomato.
• Pb (Table 4 values): wheat (0.566) > rice (0.446) > potato (0.028) > leek (0.022) > lettuce (0.018) > carrot (0.016) > tomato (0.011) > onion (0.009).
• Cd (text): rice > wheat > tomato > lettuce > leek > potato > onion > carrot.
• Cd (Table 4 values): rice (0.225) > wheat (0.212) > potato (0.021) > leek (0.008) > carrot (0.007) > lettuce (0.006) ≈ onion (0.006) > tomato (0.005).

See Verification notes — Table 4 numerics are internally consistent (EDI = C × FIR / bw recomputes verbatim from the table’s own consumption and concentration values); the text rank-orders are typographic, not data, errors.

Exceedance summary (counts derived from Tables 2–3 percentages)

• Pb above EU MAC: carrot 2/50 (4 %), wheat 5/50 (10 %), rice 4/50 (8 %); zero in potato, onion, tomato, lettuce, leek.
• Cd above EU MAC: zero in every commodity.

Methods (brief)

Study design. Cross-sectional market-basket survey of eight commodities across Hamadan province, western Iran (capital Hamadan, lat 33°33′–35°48′ N, long 47°45′–49°36′ E), August 2017 – February 2018. Fifty composites per commodity, each composite 2.5 kg, with a 1 kg subsample processed for analysis. n=400 total composites; measurements in triplicate per composite.

Sample preparation. Each composite washed with distilled water, sliced, oven-dried at 75 °C (Memmert GmbH, Schwabach, Germany), finely powdered in a mixer. 0.5 g of dried powder + 3:1 (v/v) HNO₃ (65 %) / H₂O₂ (35 %) digested in a Teflon vessel by a five-step microwave program (1.5 min 240 W → 2.5 min 100 W → 1.5 min 240 W → 4 min 300 W → 4 min 600 W). 10 mL deionised water added; filtered through 0.45 µm membranes. Moisture content determined separately on a second aliquot dried at 105 °C to constant weight (expressed % w/w).

Containers. Acid-washed per a previously published in-group protocol (Heshmati et al. 2017, ref [24]).

Instrumentation. Graphite-furnace atomic absorption spectrophotometer (CE 3300, Thermo Scientific, Waltham, MA) with hollow-cathode lamps at 217 nm (Pb) and 228.8 nm (Cd).

Calibration & QC. External calibration over 2.5–1000 µg/L (Cd Y = 0.21345X + 0.0118, r² 0.9972; Pb Y = 0.06541X + 0.03456, r² 0.9987). LOD = 3σ_blank/slope, LOQ = 10σ_blank/slope (Cd LOD 0.220 / LOQ 0.682 µg/kg; Pb LOD 0.350 / LOQ 1.090 µg/kg). Recovery validation at 0.025, 0.25, 0.5 µg/g spike levels across both vegetable and cereal matrices yielded 95.14–106.98 % recovery, RSD < 2 %. No certified reference material (CRM) reported; recovery is the sole accuracy control.

Speciation. Total Pb and total Cd only. No arsenic or mercury panel; no Pb or Cd species fractionation.

Reporting basis. Both wet-weight and dry-weight means are tabulated (Tables 2, 3, columns 4–5); risk-assessment EDIs (Table 4) use wet-weight mean concentrations and Iranian per-capita raw-commodity consumption figures (FIR, g/day) from Institute of Standards and Industrial Research of Iran (ISIRI) Standard No. 12968 (2010). All vegetables are treated as raw/as-consumed; wheat and rice as bulk grain.

Risk-assessment formulas. EDI (µg/kg bw/day) = C_mean (mg/kg ww) × FIR (g/day) / bw (kg), with implicit unit handling that yields µg/kg/day (recomputed verbatim from Table 4 inputs). THQ = EDI / RfD; TTHQ = Σ THQ across commodities; MOE = 1.2 (µg/kg bw/day) / EDI Pb. RfD Cd = 1 µg/kg bw/day (USEPA, oral chronic). bw = 70 kg, single adult cohort.

Statistics. SPSS v16.0 (SPSS Inc., Chicago, IL). One-sample t-test for comparison of analyte means to EU MAC values. One-way ANOVA with Duncan post-hoc test for between-commodity comparisons. α = 0.05.

Geographic context. Hamadan province population ~1,758,268; area 19,545.82 km². Authors describe the regional climate as cold winters and mild summers, citing Sadeghi et al. 2017 for the rainfall-altitude distribution. The paper does not investigate contamination pathway (soil, irrigation water, fertilizer, post-harvest handling, packaging) for any exceedance.

Implications

This source contributes Iranian market-basket occurrence data for total Pb and total Cd in eight bulk vegetable and cereal commodities sampled across one western Iranian province (Hamadan), plus an adult-only single-cohort exposure assessment using ISIRI 2010 per-capita consumption values. Its principal contributions to the wiki evidence pool:

• Bulk vegetable Pb occurrence (mg/kg ww and mg/kg dw) for six produce commodities in an Iranian regional market context: potato 0.029 / 0.110, onion 0.016 / 0.138, tomato 0.007 / 0.118, lettuce 0.022 / 0.319, leek 0.040 / 0.388, carrot 0.029 / 0.202. Leek and lettuce sit at or near the EU 0.30 mg/kg ww leafy-vegetable Pb MAC on a wet basis; on a dry basis lettuce 0.319 and leek 0.388 exceed the corresponding 0.30 mg/kg figure but the regulation is expressed in wet weight, so the wet-basis comparison is the operative one. Useful as central-tendency Iranian-market occurrence data for downstream pooling.
• Bulk grain Pb occurrence: wheat 0.123 mg/kg ww (10 % MAC exceedance at 0.20 mg/kg) and rice 0.097 mg/kg ww (8 % MAC exceedance). Adds Iranian-market occurrence data to the bulk-grain Pb evidence pool alongside other regional Iranian surveys (Tabriz, Shahre Rey, Isfahan, Kermanshah cited in the paper’s discussion).
• Bulk vegetable Cd occurrence (mg/kg ww and mg/kg dw): potato 0.022 / 0.088, onion 0.011 / 0.106, tomato 0.003 / 0.060, lettuce 0.007 / 0.108, leek 0.015 / 0.155, carrot 0.013 / 0.094. All below EU MAC on the wet basis; useful as low-to-moderate-end Cd occurrence values.
• Bulk grain Cd occurrence: wheat 0.046 mg/kg ww, rice 0.049 mg/kg ww; both below the EU 0.20 mg/kg ww MAC and below the contemporaneous Kermanshah-province Pirsaheb et al. 2016 wheat figure (0.41 mg/kg dw) cited in the discussion.
• Carrot, wheat, and rice MAC exceedance rates at the sample level (4 %, 10 %, 8 % respectively) document that despite below-MAC commodity means, a non-trivial fraction of sampled lots exceed the regulatory ceiling — useful evidence for downstream Part 9 synthesis of within-commodity Pb variability and for product-page Levers framing.
• Adult exposure parameter set: documents Iranian per-capita raw-commodity consumption (FIR) values from ISIRI Standard No. 12968 (2010) and the resulting EDIs at 70 kg body weight for one ranking of bulk vegetables and cereals; demonstrates that even with wheat and rice each contributing 322 g/day, the total Cd EDI of 0.49 µg/kg bw/day stays below the JECFA 0.8 µg/kg bw/day PTDI.
• Methodological reference point: GF-AAS LOD 0.220 µg/kg (Cd) and 0.350 µg/kg (Pb) with microwave digestion and HNO₃/H₂O₂; no CRM-anchored accuracy validation. The absence of CRM validation is the primary contributor to B-tier evidence grading.

Sample size is moderate (50 composites per commodity, triplicate measurements). The single-province sampling footprint, single-year window (August 2017 – February 2018), 70-kg adult-only exposure cohort, and lack of CRM-anchored accuracy validation limit the paper’s standalone authority; pools with other Iranian and regional vegetable/cereal surveys rather than anchoring any standalone characterisation. The paper does not measure arsenic (As), Hg, nickel (Ni), aluminum (Al), or tin (Sn); it does not investigate Pb or Cd contamination pathway; and the EDI rank-order statements in the text contradict the EDI values printed in Table 4 (see Key numbers and Verification notes).

Related evidence

• Lead
• Cadmium
• Potatoes
• Onions
• Tomato
• Lettuce
• Carrot
• Wheat
• Rice
• Vegetables
• Cereals
• Leafy Vegetables
• Root vegetables
• Non-root vegetables
• Root and Tuber Vegetables
• Non-Root Vegetables
• Leafy / Green Vegetables, Other
• Rice (white, brown, wild — bulk grain)
• Other grain products (oat, millet, quinoa, barley)
• Commission Regulation (EC) No 1881/2006 setting maximum levels for certain contaminants in foodstuffs
• JECFA — Provisional Tolerable Monthly Intake for Cadmium, 25 µg/kg b.w./month
• JECFA — Lead Provisional Tolerable Weekly Intake (Withdrawn 2010)
• EPA IRIS — Cadmium Oral Reference Doses

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