Health Risks from Heavy Metals via Consumption of Cereals and Vegetables in Isfahan Province, Iran

Overview

This Iranian market-basket survey quantifies total lead, arsenic, nickel, zinc, and copper in 70 edible-part samples of nine commodities — onion, leek, potato, lettuce, spearmint, basil, carrot, rice, and wheat — collected from wholesaler outlets and supermarkets across six urban cities of Isfahan province, central Iran. Samples were washed, oven-dried at 70 °C, dry-ashed at 550 °C for 8 h, dissolved in 2 M HCl, and quantified on a PerkinElmer Optima 7300 DV ICP-OES; concentrations are reported on a fresh-weight basis as 95 % upper confidence limits on the means (Pro UCL v4.00.02). The 95 % UCL lead (Pb) concentrations in carrot (0.8 mg/kg), leek (0.76 mg/kg), lettuce (0.79 mg/kg), spearmint (1.71 mg/kg), and basil (1.55 mg/kg) exceeded the 0.3 mg/kg WHO/FAO permissible limit cited by the authors; rice arsenic (As) (0.25 mg/kg) exceeded the 0.15 mg/kg Iranian Institute of Standards and Industrial Research (ISIRI) limit cited by the authors; all nickel (Ni), Zn, and Cu values fell below the cited WHO/FAO permissible limits. USEPA-style multi-cohort exposure and risk assessment across 10 receptor groups (children <6 girls/boys; 7–14 girls/boys; 14–18 girls/boys; adult women/men 18–54; >55 women/men) yielded total non-carcinogenic hazard quotients > 1 for both As and Pb across all age groups, and total carcinogenic risk for As slightly > 1×10⁻⁴ for all age groups, with wheat contributing 75–80 % of total As intake and 75–79 % of total Ni and Zn intake.

Key numbers

95 % upper confidence limits on mean fresh-weight concentrations (mg/kg) by commodity and metal (Table 2, p. 24):

Commodity	n	Ni	Zn	Cu	Pb	As
Basil	8	1.44	31.92	17.29	1.55	N.D.
Carrot	8	0.76	13.5	8.9	0.8	N.D.
Leek	8	0.86	28.15	49.09	0.76	N.D.
Lettuce	8	1.11	26.25	12.27	0.79	N.D.
Onion	8	0.72	22.03	10.76	0.25	0.85
Potato	8	0.27	15.28	5.17	0.1	N.D.
Spearmint	8	1.65	28.94	20.33	1.71	N.D.
Rice	6	0.27	53.56	0.85	0.25	0.25
Wheat	8	0.91	30.53	5.68	N.D.	0.25

Reference values cited by the authors for benchmark comparison (Results and Discussion, p. 8):

WHO/FAO permissible limits cited for Pb, Zn, Cu, and Ni: 0.3, 99.40, 73.30, and 67.9 mg/kg, respectively.
ISIRI permissible limit for As cited at 0.15 mg/kg (Institute of Standards and Industrial Research of Iran 2010, p. 9).
Pb exceedances of the 0.3 mg/kg WHO/FAO limit: carrot (0.8), leek (0.76), lettuce (0.79), spearmint (1.71), basil (1.55) mg/kg.
As exceedance of the 0.15 mg/kg ISIRI limit: rice (0.25 mg/kg).
Ni, Zn, and Cu in all nine commodities below the respective WHO/FAO limits.

Oral reference doses and slope factors used (Methods, p. 7):

RfD (mg/kg/day): Ni 0.02, As 0.0003, Pb 0.00035 (USEPA 2003, 2007).
Cancer slope factor (mg/kg/day)⁻¹: As 1.5, Pb 8.5×10⁻³ (USEPA 2005).

Total non-carcinogenic hazard quotient (THQ; sum across nine commodities) by metal, quoted from the Total Risk prose (pp. 12–13):

Pb: cumulative risk of Pb 4.8–5.8 across the children cohorts and 2.2–3.0 across the adult cohorts (p. 13); all groups > 1. Figure 1 shows boys 7–14 as the tallest Pb bar.
As: total risk of As 4.2–4.5 across the children cohorts and 3.8–10.1 across the adult cohorts (p. 12); all groups > 1. Figure 1 shows boys 7–14 as the tallest As bar.
Ni: total health hazard < 1.0 for all age groups (p. 13), Figure 1 range approximately 0.1–0.55.
Rice-only Pb HQ (Figure 1 contributions, p. 11 prose): 1.1 for girls 7–14 and 1.3 for boys 7–14.

Total cancer risk by metal and receptor group (Total Risk prose, p. 13 and Figure 2):

Pb: total cancer risk for all age groups in the acceptable 10⁻⁶ to 10⁻⁴ band; for children <6 and 14–18 cohorts, total Pb cancer risk < 1×10⁻⁶; for other age groups total Pb cancer risk > 1×10⁻⁶ (p. 13). Figure 2 reads the highest Pb total cancer risk near 3×10⁻⁶.
As: total combined cancer risk 1×10⁻⁴ for children and 1.3×10⁻⁴ to 8.4×10⁻⁴ for adults (p. 13). The authors note this is “slightly higher than an acceptable risk (10⁻⁶–10⁻⁴)“. For several receptor groups (girls/boys 7–14, girls 14–18, average women/men, >55 women/men) the As cancer risk from wheat consumption alone exceeded 1×10⁻⁴ (p. 12).

Receptor-group exposure ranking and dominant pathways (Daily Intakes section, pp. 9–11):

Wheat is the main route for Zn intake in all receptor groups, contributing approximately 75–79 % of total daily dietary Zn.
Wheat is the main route for Ni intake in all receptor groups, contributing approximately 75–79 % of total daily dietary Ni.
Wheat contributes approximately 75–80 % of total daily dietary As intake; rice ≈ 15 %; onion ≈ 5–9 %.
Daily Zn ranking (children): wheat > rice > potato > lettuce > onion > basil > spearmint > carrot > leek.
Daily Zn ranking (adults): wheat > rice > potato > lettuce > leek > onion > spearmint > carrot > basil.
Children: rice and lettuce are main contributors to total Pb intake.

Dietary intake comparisons (Daily Intakes section, pp. 9–10):

Adult Pb dietary intake from cereals + vegetables less than the FAO/WHO 1991 tolerable daily Pb intake of 3.57 µg/kg bw/day (cited).
Children Ni dietary intake less than the ATSDR 2000 reference dose of 0.017 mg/kg bw/day.
As intake less than the WHO/FAO 2011 provisional tolerable daily intake of 3 µg/kg bw/day.
Total Cu intake higher than the NRC 2001 RDA but less than the tolerable upper intake level (3–10 mg/day across receptor groups).
Vegetables alone supply approximately 19.5 %, 53.6 %, 47.6 %, 39 %, and 53.6 % of the Zn RDA for children <6, 7–14 years, girls 14–18, and male and female adults, respectively (NRC 2001).

Exposure parameters used (Table 1, pp. 22–23):

Exposure duration: children <6 = 4 y; 7–14 = 7 y; 14–18 = 4 y; adults 18–54 = 27 y; >55 = 15 y.
Exposure frequency: 365 d/y across all cohorts.
Bodyweight (kg): children <6 girls 17.5 / boys 18.7; 7–14 girls 35 / boys 29; 14–18 girls 56 / boys 59.1; adults women 61 / men 76.4; >55 women 60.6 / men 65.1.
Ingestion rate, children <6 vs adult (g/d): rice 27 vs 110; wheat 151.9 vs 531.51; potato 35 vs 123.29; onion 2.9 vs 19.2; carrot 2.9 vs 8; leek 1 vs 19.9; lettuce 7.3 vs 29.3; spearmint 2 vs 9; basil 2 vs 9.
Adult Zn RDA = 11 mg/d (men), 8 mg/d (women); Cu RDA = 0.9 mg/d (NRC 2001).

Methods (brief)

Sample collection. Seventy edible-part composite samples from nine commodities (onion, leek, potato, lettuce, spearmint, basil, carrot, rice, wheat) were collected from wholesaler outlets and supermarkets in six urban cities of Isfahan province, central Iran (Isfahan, Najabad, Shahinshahr, Zarinshahar, Falvarjan, Dorcheh — author spellings as published). Three subsamples were collected from different outlets for the same plant. Per-commodity counts: 8 composites for all commodities except rice (6 composites). Sampling year is not stated in the published text. The paper does not state whether samples were drawn within one growing season or across multiple seasons, and does not state composite mass or subsample protocols beyond the three-subsample-per-plant statement.

Sample preparation. Vegetable samples were washed several times with tap water and final-rinsed with distilled water. Samples were oven-dried at 70 °C to constant weight. Dry samples were combusted at 550 °C for 8 h. The resulting ash was dissolved in 2 M HCl (Chapman and Pratt 1961 cited for the dry-ashing protocol). The paper does not state explicit digest volumes, dilution factors, or moisture-content conversion factors.

Instrumentation. Total Ni, Zn, Cu, Pb, and As in the digest solution were determined by inductively-coupled plasma optical emission spectrometry on a PerkinElmer Optima 7300 DV ICP-OES (USA). The paper does not state ICP-OES wavelengths, certified reference materials, method detection limits beyond the qualitative “N.D.” indicator in Table 2, recovery values, or replicate-precision statistics.

Statistical analysis. Concentrations reported as 95 % upper confidence limits on the means of the per-commodity composite samples, computed in Pro UCL version 4.00.02. Descriptive statistics other than the 95 % UCL means are not published. Inferential tests and inter-commodity statistical comparisons are not reported.

Exposure and risk assessment. Daily intake of each metal was computed via the USEPA 1989 ingestion equation Intake = (C × IR × FI × EF × ED)/(BW × AT) where C is contaminant concentration in food (mg/g), IR is ingestion rate (g/d), FI is fraction ingested from contaminated source (set to 0.5 in this study to account for un-modeled water, soil-ingestion, and inhalation pathways), EF is exposure frequency (d/y), ED is exposure duration (y), BW is bodyweight (kg), and AT is averaging time (365 × ED for non-carcinogenic, 365 × 70 for cancer assessment). Non-carcinogenic hazard quotient (HQ) was computed as HQ = intake / RfD using USEPA RfDs 0.02 (Ni), 0.0003 (As), 0.00035 (Pb) mg/kg/day. Total non-carcinogenic risk was computed as sum HQ_i across the nine commodities (USEPA 2007 cumulative-risk framework). Cancer risk was computed as Risk = CDI × SF using cancer slope factors of 1.5 (As) and 8.5×10⁻³ (Pb) (mg/kg/day)⁻¹ from USEPA 2005. Ten receptor cohorts were modelled: children <6 (girls / boys); children 7–14 (girls / boys); teenagers 14–18 (girls / boys); average adults 18–54 (women / men); old adults >55 (women / men). Exposure-parameter sources are Yeganeh et al. 2012 (exposure duration, frequency, rice/wheat/potato ingestion rates), USEPA 1997 (bodyweights), Chavoshi et al. 2011 (onion/carrot/leek/lettuce/spearmint/basil ingestion rates), and NRC 2001 (RDA Zn and Cu). Vegetable Zn and Cu daily intakes compared against NRC 2001 RDA tabulated in Table 1.

Speciation. ICP-OES quantifies total elemental concentrations; no As speciation (no inorganic arsenic (iAs)/total arsenic (tAs) separation), no mercury (Hg) measurement, no chromium (Cr) speciation. The metals: field uses tAs for total arsenic, Pb for total lead, Ni, Zn, Cu abbreviation vocabulary.

Reference values used by the authors. WHO/FAO permissible limits for Pb (0.3), Zn (99.40), Cu (73.30), Ni (67.9) mg/kg (citation attribution as published — the paper cites these as WHO/FAO limits without specifying the underlying document; FAO/WHO 1991 Codex Alimentarius Vol. XII Supplement 4 and FAO/WHO 2001 / 2011 Codex Food Additives and Contaminants documents are cited in the References). ISIRI 12968 (Institute of Standards and Industrial Research of Iran 2010) cited for the 0.15 mg/kg As limit. FAO/WHO 1991 tolerable daily Pb intake of 3.57 µg/kg bw/day cited. ATSDR 2000 Ni reference 0.017 mg/kg bw/day cited. WHO/FAO 2011 provisional tolerable daily As intake of 3 µg/kg bw/day cited. USEPA 1989, 1997, 1998, 1999, 2003, 2005, 2007 cited for the risk-assessment framework, exposure parameters, RfDs, and slope factors.

Implications

This source contributes Iranian market-basket occurrence data for total Pb, total As, Ni, Zn, and Cu in nine cereal and vegetable commodities purchased from wholesalers and supermarkets in six urban cities of Isfahan province, central Iran, with USEPA-style multi-cohort exposure and risk assessment across ten receptor groups. Principal contributions to the wiki evidence pool:

A Pb 95 % UCL signal exceeding the 0.3 mg/kg WHO/FAO permissible limit cited by the authors in five of nine commodities — carrot (0.8 mg/kg), leek (0.76 mg/kg), lettuce (0.79 mg/kg), spearmint (1.71 mg/kg), and basil (1.55 mg/kg) — and a Pb signal in rice at 0.25 mg/kg (below the cited limit). The 95 % UCL basis means these are upper-bound estimates of the mean, not per-sample maxima.
A total As (tAs) 95 % UCL signal of 0.25 mg/kg in both rice and wheat (above the 0.15 mg/kg ISIRI Iranian standard cited by the authors) and 0.85 mg/kg in onion, with non-detects in basil, carrot, leek, lettuce, potato, and spearmint. No speciation was performed; the dataset cannot distinguish iAs from organic arsenic, which limits its applicability to the iAs-focused regulatory thresholds typical of rice-as-grain frameworks.
A Ni, Zn, and Cu signal in all nine commodities below the WHO/FAO permissible limits cited by the authors. The Cu value of 49.09 mg/kg in leek is the highest single per-commodity value in the dataset and is well below the cited 73.30 mg/kg WHO/FAO Cu limit but is high relative to typical Cu concentrations in non-allium vegetables.
A multi-cohort total non-carcinogenic hazard assessment with THQ > 1 for both As and Pb across all ten receptor cohorts (highest Pb THQ in 7–14 year-old children at 4.8–5.8; highest As THQ in 7–14 year-old children at 10–11). The authors interpret this as a population-level health risk signal.
A total combined As cancer risk of 1×10⁻⁴ for children and 1.3×10⁻⁴ to 8.4×10⁻⁴ for adults (p. 13), exceeding the upper bound of the authors’ cited acceptable 10⁻⁶ to 10⁻⁴ band. Wheat consumption alone drove As cancer risk > 1×10⁻⁴ for the majority of adult cohorts. The authors interpret this as a possible cancer risk to local consumers; the wheat-dominance of As intake is consistent with the high per-capita wheat ingestion in Iranian dietary patterns (151.9 g/d for children <6 and 531.51 g/d for adults per the cited Yeganeh 2012 figures).
A small-panel (n=70 composites, 6 cities, no sampling year), peer-reviewed (Taylor & Francis) dataset with no certified-reference-material recovery values, no method detection limits beyond qualitative N.D., no As speciation, no per-sample raw data, and a 95 % UCL-only summary statistic. The B-tier classification reflects these limitations; the source should pool with other Iranian market-basket surveys for occurrence-distribution purposes rather than anchor any standalone characterisation.
Companion to wiki/sources/salehi2013-iran-isfahan-lenjanat-vegetables-cd-pb (Cd and Pb in Lenjanat agricultural soils and vegetables) and wiki/sources/moradi2015-iran-isfahan-soil-crops-metals (heavy metals in Isfahan industrial-site soils and crops) for Isfahan-province occurrence pooling.

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