Dghaim et al. 2015 — Heavy metals in traditional herbs consumed in the UAE

This peer-reviewed primary study from Zayed University (Dubai) measured cadmium, lead, copper, iron, and zinc in 81 samples of seven traditional herbs purchased from 13 authenticated Dubai-municipality-approved shops and supermarkets. All concentrations are expressed on a dry-weight basis after fresh samples were air-dried at room temperature and powdered. Microwave-assisted digestion followed US-EPA Method 3052 (HNO3/HCl/H2O2 in a CEM MARS microwave system); metals were quantified by AAS (Varian AA240FS). The headline finding is that 64% of all samples exceeded the WHO/FAO permissible limit (PL) for lead in medicinal herbs (10 mg/kg dry weight), and 29% of cadmium-analyzed samples exceeded the WHO/FAO PL for cadmium (0.3 mg/kg). Lead contamination was particularly high in sage (100% of samples above PL), thyme (91%), basil (90%), and oregano (90%), with individual maxima of 16-23 mg/kg. Cadmium exceedances were most prevalent in basil (80%) and sage (66%). The paper does not measure arsenic or mercury.

Key numbers

Cadmium (Cd) — concentration range (mg/kg dry weight, Table 2; ”**” = below Method Quantification Limit of 0.1 mg/kg):

• All herbs combined: <0.1 to 1.11 mg/kg
• Mint: ND (Cd not detected in any of 13 samples; 0/13 above PL of 0.3)
• Parsley: <0.1 to 0.21 ± 0.07 mg/kg (0/13 above PL)
• Chamomile: <0.1 to 0.82 ± 0.02 mg/kg (5/9 = 55% above PL)
• Basil: 0.13 ± 0.01 to 1.11 ± 0.07 mg/kg (8/10 = 80% above PL)
• Sage: <0.1 to 0.88 ± 0.08 mg/kg (6/9 = 66% above PL)
• Oregano: <0.1 to 0.35 ± 0.02 mg/kg (1/11 = 9% above PL)
• Thyme: <0.1 to 0.63 ± 0.07 mg/kg (3/11 = 27% above PL)
• Overall: 29% of all Cd-analyzed samples above WHO/FAO PL of 0.3 mg/kg

Lead (Pb) — concentration range (mg/kg dry weight, Table 2; ”**” = below MQL of 1 mg/kg):

• All herbs combined: <1.0 to 23.52 mg/kg
• Mint: 1.44 ± 0.67 to 9.24 ± 1.02 mg/kg (0/13 above PL of 10)
• Parsley: <1.0 to 12.83 ± 0.97 mg/kg (6/13 = 46% above PL)
• Chamomile: 5.37 ± 1.25 to 11.40 ± 1.32 mg/kg (4/9 = 44% above PL)
• Basil: 9.01 ± 0.28 to 16.15 ± 2.53 mg/kg (9/10 = 90% above PL)
• Sage: 12.66 ± 1.54 to 21.76 ± 1.33 mg/kg (10/10 = 100% above PL)
• Oregano: 9.39 ± 1.77 to 18.06 ± 2.32 mg/kg (10/11 = 90% above PL)
• Thyme: 9.07 ± 0.34 to 23.52 ± 1.68 mg/kg (11/12 = 91% above PL)
• Overall: 64% of all samples above WHO/FAO PL of 10 mg/kg

Note: The WHO/FAO permissible limit of 10 mg/kg for Pb in medicinal herbs is far above EU 1881/2006 limits (3 mg/kg for dried herbs at the time of publication, with subsequent tightening under EU 2023/915). The high exceedance rates against the WHO/FAO PL should be read with that regulatory contrast in mind.

Copper (Cu): all-herb range 1.44-156.24 mg/kg; max by herb (mint 12.32, parsley 13.29, chamomile 12.99, basil 18.87, sage 156.24, oregano 41.64, thyme 13.16 mg/kg); 12% of all samples above the Chinese PL of 20 mg/kg (no WHO/FAO PL established for Cu in herbs); one sage sample above the Singapore PL of 150 mg/kg. Per-herb Cu exceedances vs Chinese PL 20 mg/kg (Table 2): mint 0% (0/13), parsley 0% (0/13), chamomile 66% (6/9), basil 0% (0/10), sage 18% (2/11), oregano 18% (2/11), thyme 0% (0/12).

Zinc (Zn): all-herb range 12.65-146.67 mg/kg; max by herb (mint 52.97, parsley 50.10, chamomile 38.93, basil 112.19, sage 58.78, oregano 37.28, thyme 146.67 mg/kg); 19% of samples above the WHO/FAO PL of 50 mg/kg. Exceedances by herb: mint 7% (1/13), parsley 7% (1/13), chamomile 0%, basil 50% (5/10), sage 36% (4/11), oregano 0%, thyme 38% (5/13).

Iron (Fe): all-herb range 81.25-1,101.22 mg/kg; max by herb (mint 821.01, parsley 605.50, chamomile 581.30, basil 1,101.23, sage 799.31, oregano 420.52, thyme 764.51 mg/kg). No WHO PL established for Fe in herbs.

Methods (brief)

Sample preparation: 81 herb samples (7 species; local and imported, fresh and dried) purchased from 13 authenticated shops/supermarkets approved by Dubai municipality. Fresh samples air-dried at room temperature; all samples powdered, sieved, and stored in plastic bags. Three subsamples averaged per source.

Digestion: US-EPA Method 3052 microwave-assisted digestion. 0.5 g sample weighed into a MARSXpress digestion vessel; 0.5 mL 37% HCl (Suprapur, Merck), 9.0 mL 69% HNO3 (Suprapur, Merck), and 1 mL 30% H2O2 (Sigma-Aldrich) added; digested in a CEM MARS microwave system. Digestate filtered, transferred to 25 mL volumetric flask, diluted with 0.2% HNO3.

Quantitation: AAS (Varian AA240FS, Australia). Multi-element standards prepared from 1,000 mg/L stock solutions (Fluka TraceCert Ultra, Sigma-Aldrich) in 5% HNO3. Calibration linear, r = 0.995. Glassware/digestion vessels soaked in 20% HNO3 and rinsed with ultrapure water (Millipore Elix Advantage). Method Quantification Limits: 0.1 mg/kg for Cd; 1 mg/kg for Pb. Concentrations expressed as mean ± SD of three subsamples (mg/kg dry weight). Replicate analysis and calibration checks reported as QC.

Limitations and scope: small per-herb n (9-13 samples); only total metals measured, with no speciation for As (not measured) or Hg (not measured); single market (Dubai), mix of local and imported product with origin not separately reported within each herb type; no breakdown of fresh vs dried within each herb type even though both were purchased; 2015 data; the paper benchmarks against the WHO/FAO 10 mg/kg PL for Pb and 0.3 mg/kg PL for Cd in medicinal herbs (drawn from WHO Quality Control Methods for Medicinal Plant Materials and WHO Guidelines for Assessing Quality of Herbal Medicines), which are higher than EU food limits for the dried-herb matrix.

Implications

• Certification: this study contributes UAE-market occurrence evidence for Pb and Cd in dried culinary/medicinal herbs (sage, oregano, thyme, basil, chamomile, parsley, mint). It does not measure As or Hg. Per-herb upper bounds in this dataset reach 21-23 mg/kg dry weight for Pb in sage and thyme — values that exceed the EU 1881/2006 dried-herb limit (3 mg/kg) by roughly an order of magnitude, even though they sit below or near the WHO/FAO medicinal-herb PL of 10 mg/kg invoked by the authors. High-Pb herbs in this dataset: sage, oregano, basil, thyme. High-Cd herbs: basil, sage, chamomile.
• Courses: an illustrative case for geographic sourcing effects on herb contamination. The pattern of high Pb in Mediterranean-origin herbs (sage, oregano, basil, thyme) sold through a Middle East retail channel is teachable material for sourcing modules covering origin-region risk and supply-chain due diligence.
• App: per-herb dry-weight Pb ranges from this dataset (sage 12.66-21.76; thyme 9.07-23.52; basil 9.01-16.15; oregano 9.39-18.06 mg/kg dry weight) can contribute to the ingredient contamination_profile blocks for these species once Part 9 synthesis runs; the paper provides one A-tier occurrence dataset for the UAE retail channel.

Provenance notes

Open-access article distributed under the Creative Commons Attribution License (CC BY) per the title page. Hindawi publication; article ID 973878. PDF retrieved via the manual-fetch Kimi sweep into raw/Manual Fetch Kimi /condiment_papers/05_PB_Vanilla_Spices/. Source DOI 10.1155/2015/973878 confirmed against article header.

The source paper carries a minor internal inconsistency: Table 1 lists 81 total samples (mint 13, parsley 13, basil 11, sage 11, oregano 11, thyme 13, chamomile 9), but Table 2’s percentage-above-PL denominators differ slightly for some herbs (e.g., basil 8/10 and 9/10 for Cd and Pb, sage 6/9 for Cd vs 10/10 for Pb, thyme 11/12 for Pb). The Section 3.1 text states “78 herb samples analyzed for cadmium.” Per-cell denominators from Table 2 are preserved verbatim here; the discrepancy is in the source.

Verification notes

• 2026-05-28 merge-enhance (Claude Opus 4.7, autonomous v2.0 manual-fetch skill). EXISTING path: DOI grep against wiki/sources/ matched this same page (dghaim2015-heavy-metals-uae-herbs.md, DOI 10.1155/2015/973878). Prior page dated updated: 2026-05-14, flagged advisory in data/evidence/routing_malformed.csv for missing optional routing-input fields. Full PDF re-read end-to-end (6 pages, single-file; tables 1 and 2 re-verified).
• Preserved from prior page: cite_key (dghaim2015-heavy-metals-uae-herbs), license (CC BY — verified against title-page copyright statement), near_duplicates (empty), source_type (peer-reviewed), evidence_tier (A), sample_n (81), publication, authors.
• raw_handle updated from legacy manual-fetch-kimi (folder placeholder, not a unique handle) to MFK_determination-of-heavy-metals-concentration-in-tra per current MFK_-prefix convention used by sibling Manual Fetch Kimi sources (aldayel2018, abdolahpour2023, etc.).
• raw_path corrected from "raw/Manual Fetch Kimi/condiment_papers/05_PB_Vanilla_Spices/Determination of Heavy Metals Concentration in Traditional Herbs .pdf" (missing trailing space in parent directory name and truncated filename) to the actual path with the trailing-space convention preserved and the full filename ...Commonly Consumed in the United Ara.pdf.
• raw_sha256 added: 62cc1c5e953dadcfa4340f54b1658e0c2aed19350b1ab8ce069977f3ea209c4e (computed locally from the PDF).
• access_url added: https://doi.org/10.1155/2015/973878 (DOI canonical resolver).
• no_doi_assigned: false added to match the current source-page schema (DOI is present).
• metals: expanded from [Pb, Cd] to [Pb, Cd, Cu, Fe, Zn]. The paper measures and reports all five elements with full ranges and exceedance statistics; restricting to Pb/Cd omitted the Cu, Fe, and Zn occurrence data that the paper carries. As and Hg are NOT added because the paper does not measure them.
• ingredients: expanded to include [[ingredients/sage]], which was missing from the prior page despite sage being one of the seven herbs measured (and the highest Pb herb, 100% above PL). Also added [[ingredients/dried-herbs]] as the broad-matrix umbrella since all samples are reported on dry-weight basis. Per-species slugs (basil, sage, oregano, mint, thyme, chamomile) do not currently exist as wiki ingredient pages; per CLAUDE.md Part 10 + the skill’s no-new-ingredient-pages rule, those slugs are left in the frontmatter so the auto-stub script can pick them up at freq-2.
• matrices: corrected from [herbs, dry-weight] to [herbs, dried-herbs]. dry-weight is a basis, not a matrix; the dry-weight basis is documented in prose. dried-herbs matches the corpus-established matrix vocabulary used by sibling herb-spice sources (cicero2022, kowalska2021, lhaac2025-csp41).
• jurisdictions: corrected from [UAE] to [AE] per ISO-3166 two-letter convention used across the corpus.
• sample_population expanded to include per-herb n breakdown (mint 13, parsley 13, basil 11, sage 11, oregano 11, thyme 13, chamomile 9) per Table 1, plus the 13-shop sourcing detail and dry-weight basis explicitly.
• Legacy heading ## Wiki pages updated on ingest removed. Replaced by the standard ## Verification notes + ## Provenance notes structure per current Part 6 / v2.0 template; downstream wiki pages this source routes to are derived from frontmatter by the routing layer, not maintained as a body-list.
• Section structure aligned to current v2.0 template: intro paragraph, Key numbers, Methods (brief), Implications, Provenance notes, Verification notes. Numerical content preserved with per-herb ranges and PL-exceedance percentages expanded to include the SD values from Table 2.
• Numerical fidelity re-verified against the PDF tables. Spot-checks: Cd overall 29% (text and Table 2 footer); Pb overall 64% (text and Table 2 footer); Cu overall 12% (Section 3.3); Zn overall 19% (Section 3.4); per-herb max values cross-verified against Table 2 ranges and Section 3.1-3.5 narrative. Sage Pb 100% (10/10) preserved as in Table 2 despite Table 1 reporting sage n=11 (source-internal denominator discrepancy noted in Provenance notes; not a wiki-side error).
• Part 12 brand firewall: no brand names appear in source-page body. Method-section vendors (Suprapur/Merck, Sigma-Aldrich, Fluka TraceCert Ultra, Varian AA240FS, CEM MARS, Millipore Elix Advantage) are scientific-method vendors and are PERMITTED per the 2026-05-17 strict-reading Exception 2 (instrument/reagent/reference-material naming is scientific reproducibility, not brand attribution to contamination values).
• Part 2 wiki/HMTc firewall: Implications section describes what the paper contributes (occurrence dataset, high-risk-herb pattern); it does not propose HMTc thresholds, does not synthesize across other literature, and does not issue consumer risk advisories. The contrast with EU 1881/2006 is stated as regulatory context, not as a threshold proposal.
• 2026-05-28 fresh-context audit subagent (general-purpose) verdict: PROMOTE. All five checks ✅ except two ⚠️ notes:
  • ⚠️ Check 1: per-herb Cu exceedance percentages (chamomile 66%, sage 18%, oregano 18% vs Chinese PL 20 mg/kg) from PDF page 4 §3.3 + Table 2 were absent from Key numbers. Verified against source — APPLIED: full per-herb Cu breakdown added to the Cu paragraph in Key numbers.
  • ⚠️ Check 1: minor source-internal discrepancy on mint Fe max (Table 2 “821.02 ± 17.83” vs Section 3.5 narrative “821.01”). Wiki cites the narrative value (821.01). Defensible per audit. No change; the source-internal denominator/value discrepancies are already flagged in Provenance notes generally; documenting this specific Fe instance here.
  • ⚠️ Check 2: per-species ingredient slugs (basil, sage, oregano, thyme, mint, chamomile) not in current taxonomy snapshot. Already explicitly flagged in Verification notes above per the audit-prompt Check 2 carve-out for snapshot-missing-but-disclosed slugs; auto-stub freq-2 mechanism handles promotion. No change.
  • ⚠️ Check 5: “illustrative case for geographic sourcing effects” under Courses bullet flagged as borderline-synthesis. Re-reviewed — the bullet describes one paper’s teaching utility, not a cross-paper consensus claim; acceptable per audit’s own note. No change.

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.