Asadi Touranlou et al. 2025 - Health risk from heavy metals in Iranian bread, Monte Carlo analysis

This study quantifies heavy metal contamination in 248 Iranian bread samples spanning four traditional bread types (lavash, taftoon, barbari/Barbary, sangak) across 11 provinces, then applies Monte Carlo simulation to characterize non-cancer and cancer risk for children and adults. Chromium (Cr) and iron (Fe) drive the non-cancer risk model, with hazard indices (HI) above 1 for both children and adults in the source’s 95% Monte Carlo interval. Lead (Pb) and cadmium (Cd), evaluated for cancer risk only in four provinces where they were detected, fall in the source’s moderate-risk band.

Key numbers

All concentrations below are mg/kg dry weight unless noted.

Table 1 mean concentrations (n=248 total samples):

Converted mean concentrations: Cd 4 ppb; Pb 650 ppb; Cr 1,000 ppb; Hg 30 ppb; Ni 50 ppb; Al 4,980 ppb; Fe 59,240 ppb; Zn 13,640 ppb; Cu 3,080 ppb; Co 10 ppb.

Detection rates: Fe 100%, Zn 99.59% (247/248), Al 96% (238/248), Cu 91.53% (227/248), Cr 63.30% (157/248), Pb 29% (72/248), Co 18.54% (46/248), Ni 12.50% (31/248), Hg 9.67% (24/248), and Cd 8.87% (22/248). The source text says “11 PTEs” in this sentence, but the study panel and tables contain 10 measured elements.

Table 2 regulatory-comparator outcomes: Pb mean (0.65 mg/kg) exceeds the WHO/FAO comparator (0.3 mg/kg) and the INSO comparator (0.05 mg/kg). Cd mean (0.004 mg/kg) exceeds the WHO/FAO comparator (0.003 mg/kg) but is below the INSO comparator (0.03 mg/kg). Cr (1.00 mg/kg), Hg (0.03 mg/kg), Fe (59.24 mg/kg), and Al (4.98 mg/kg) exceed the WHO/FAO comparators shown by the source. Co, Ni, Zn, and Cu are below the WHO/FAO comparators shown in Table 2. The abstract and discussion summarize the exceedance set inconsistently, so this page follows Table 2 and flags the source-side inconsistency rather than harmonizing the narrative.

Bread-type Pb means (mg/kg): lavash 0.70 +/- 1.90; taftoon 0.96 +/- 2.20; barbari/Barbary 0.57 +/- 1.39; sangak 0.46 +/- 1.40. Across bread types, only Fe (p=0.025) and Zn (p=0.014) differed significantly; taftoon had the highest Fe mean (67.41 mg/kg) and sangak had the highest Zn mean (14.64 mg/kg).

Non-cancer risk: THQ/HI calculations excluded Hg, Cd, Co, Pb, and Ni because detection rates were below 30%. Mean THQ values for adults were Al 0.044 +/- 0.027, Cr 1.346 +/- 2.640, Cu 0.454 +/- 0.236, Fe 0.281 +/- 0.545, Zn 0.291 +/- 0.107, with HI 2.416 +/- 3.555. Mean THQ values for children were Al 0.062 +/- 0.038, Cr 2.880 +/- 5.572, Cu 0.959 +/- 0.499, Fe 1.151 +/- 0.595, Zn 0.615 +/- 0.227, with HI 5.670 +/- 6.933. Monte Carlo 95% HI intervals were 3.37-8.53 for children and 1.52-3.78 for adults.

Cancer risk: Cd and Pb were evaluated only in four provinces where they were detected. Mean CR values were Pb 1.54 x 10^-5 +/- 4.02 x 10^-5, Cd 5.14 x 10^-6 +/- 2.1 x 10^-5, and total CR 2.05 x 10^-5 +/- 5 x 10^-5 for adults; Pb 6.49 x 10^-6 +/- 1.7 x 10^-5, Cd 2.17 x 10^-6 +/- 8.86 x 10^-6, and total CR 8.67 x 10^-6 +/- 2.11 x 10^-5 for children. Monte Carlo 95% CR intervals were 3.47 x 10^-6 to 1.84 x 10^-5 for children and 8.37 x 10^-6 to 4.08 x 10^-5 for adults. The paper labels these as “moderate” but prints the inequality as “10^-4 < CR ⇐ 10^-6”, a reversed expression that this page treats as a source-side notation error.

Sensitivity analysis: Cr concentration drove 45.8% of HI variance in children and 44.7% in adults. Fe was second (17.6% children, 17.4% adults). For cancer risk, Pb concentration dominated (32.2% children, 36.8% adults), followed by Cd (29.3% children, 31.8% adults).

Methods (brief)

The study analyzed 248 bread samples collected from 11 Iranian provinces during winter 2020. Bread types were lavash (n=69), taftoon (n=45), barbari/Barbary (n=70), and sangak (n=64). Samples were kept at 4 deg C, prepared as 10 g bread portions, dried at 100 deg C to constant weight, homogenized, and passed through a 2 mm sieve.

Element analysis used ICP-OES (Spectro Arcos, model 76004555, Germany) following EPA 3050B. Acids, reagents, and standard solutions were from Merck. The authors report LODs in supplemental Table S1, calibration curve r > 0.99 for each element, triplicate analysis, recovery rates of 80.5%-100.6%, and control standards every 10 samples. Concentrations were reported in mg/kg dry weight.

Risk assessment used EDI, THQ, HI, and CR equations. The RfDs used by the source were Cd 0.001, Ni 0.02, Cu 0.04, Cr 0.003, Fe 0.7, Zn 0.3, Al 0.7, Hg 0.0004, Co 0.0004, and Pb 0.0035 mg/kg-day. Cancer risk used Cd slope factor 0.38 and Pb slope factor 0.0085. Non-detects were assigned zero. Monte Carlo modeling used Crystal Ball v11.1.34190 with 10,000 iterations at 95% confidence; metal concentrations and bread-consumption rates were modeled as lognormal distributions, exposure frequency and exposure duration as uniform, body weight as normal, and averaging time as uniform.

The study measures total metals throughout. Arsenic was not in the analyte panel. Mercury is total Hg rather than methylmercury, and chromium is total Cr rather than Cr-VI.

Implications

Standards work: This source contributes Iran-market finished-bread occurrence evidence for Pb, Cd, Cr, tHg, Al, Ni, Co, Cu, Fe, and Zn, with product-form detail for lavash, taftoon, barbari/Barbary, and sangak. It is most useful as a jurisdiction-specific bread-and-baked-goods source rather than as a general wheat-flour source, because the measured matrix is finished bread and the authors discuss possible production and baking-surface contributions.

Courses: The paper is useful for teaching probabilistic risk assessment and the consequences of detection-rate decisions. The authors excluded Hg, Cd, Co, Pb, and Ni from THQ/HI because each was detected in less than 30% of samples, while assigning non-detects to zero in the broader calculations; both choices affect the resulting risk estimates.

App: The page can support occurrence-context displays for Iranian bread products, with clear labels for dry-weight basis, province-level sampling, and the distinction between total Cr/tHg and any species-specific analyte.

Wiki pages this source may touch

• aluminum
• cadmium
• chromium
• cobalt
• copper
• iron
• lead
• mercury-total
• nickel
• zinc
• wheat
• non-rice-grains
• bread
• bread-and-baked-goods

Verification notes

• Merge-enhanced 2026-05-18 from the full manual-fetch PDF path and SHA-256 recorded in frontmatter.
• Corrected the overall Zn mean to Table 1’s 13.64 +/- 4.94 mg/kg; the abstract and Table 2 print 13.6 +/- 44.94, which conflicts with Table 1 and with the bread-type distribution.
• Corrected the regulatory-comparator summary to follow Table 2: Cd exceeds the source’s WHO/FAO comparator but remains below the INSO comparator; the source’s abstract, results, discussion, and conclusion describe the exceedance set inconsistently.
• Replaced older HMTc-threshold and cross-source-comparison phrasing with source-only implications for standards work, courses, and app context.
• Identity-check note: this page is the Scientific Reports 2025 national Iranian-bread study (n=248, no arsenic analyte); it is distinct from the local page asaditouranlou2025-bread-wheat-mashhad, which covers a different Asadi Touranlou et al. 2025 bread/flour study.
• Fresh-context audit (Codex, 2026-05-18) returned REVISE with two prose concerns; generalized the software name in the opening paragraph and moved the companion-study disambiguation from the main summary to verification notes.
• Strict brand-firewall check: no consumer brands are named; instrument, reagent, and software vendor names are retained only as Methods details under the Part 12 scientific-method exception.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.