Overview
Fresh herbs — the live or freshly-cut leaves, flowers, and aerial plant parts of culinary aromatic plants (basil, parsley, cilantro, dill, mint, thyme, oregano, sage, rosemary, chives, tarragon, marjoram) — sit at the lower end of the herbs-and-spices category by per-mass concentration because the fresh form has not undergone the 7-10× concentration uplift that drying produces. Fresh herbs are commonly grown in home gardens, community gardens, urban allotments, and small-scale commercial production, which means siting variability (roadside, industrial-corridor) drives much of the within-category variance on Pb specifically. The current corpus loads 3 directly-routed sources: Fischer 2022 Polish mercury in spice plants (n=48 including fresh-leaf samples, The Mercury Concentration in Spice Plants), LHAAC 2025 Australian Coordinated Sampling Project 41 covering both fresh and dried product (n=380, Coordinated Sampling Project 41: Microbial and Heavy Metal Detections in Herbs and Spices), and Winiarska-Mieczan 2023 Polish Cd-Pb in 432 herb-and-single-component-spice samples covering fresh herbs as a subset (The Content of Cd and Pb in Herbs and Single-Component Spices Used in Polish Cuisine). The paired-product comparison with Dried Herbs establishes the fresh-vs-dried-basis factor; the same plant species at the same source carries roughly 1/8 to 1/10 the per-mass Pb-and-Cd of the dried form purely from the moisture-removal accounting.
Why this commodity accumulates heavy metals
Fresh herbs take metals through the same plant-physiology pathways as the broader leafy-vegetable category (see Leafy Vegetables): root uptake of soluble soil metals (Cd, Cr, Ni) via the transpiration stream, and direct atmospheric deposition of particulate Pb onto the leaf surface during the growing cycle. The surface-area-to-volume ratio of fresh-herb leaves (typically thin, large surface area per gram) makes them efficient collectors of atmospheric Pb relative to root vegetables or compact-head leafy vegetables. The siting of fresh-herb production is highly variable: commercial Mediterranean herb production (Italy, Greece, Spain, Turkey) is dominantly in cropland settings with managed soil and water; home-garden and urban-garden production often sits in settings with elevated soil or atmospheric Pb backgrounds (former industrial sites, roadside plots). The Polish Winiarska-Mieczan 2023 dataset (n=432 herbs and single-component spices) is the largest single-jurisdiction recent dataset for the Cd-and-Pb profile across fresh and dried product on a comparable methodological basis (The Content of Cd and Pb in Herbs and Single-Component Spices Used in Polish Cuisine). The Fischer 2022 Polish mercury-in-spice-plants work characterises the mercury profile across 48 fresh-leaf samples, finding generally low mercury but with detectable concentrations in some species (The Mercury Concentration in Spice Plants). The Australian LHAAC 2025 CSP 41 covers both fresh and dried product at scale (n=380) with the 7-metal panel (Coordinated Sampling Project 41: Microbial and Heavy Metal Detections in Herbs and Spices).
Heavy metal contamination profile
Per-analyte snapshot derived from the machine-readable contamination_profile in the frontmatter above. data gap indicates the literature has been reviewed for this commodity-analyte combination and no usable occurrence data was found (a finding, not a placeholder). The Key sources column shows the top 2-3 contributing sources by year and sample size, with numbered wikilink aliases.
| Analyte | Coverage | Typical (ppb) | Confidence | Key sources |
|---|---|---|---|---|
| Pb | n=3 | 10–300 | medium | 1 |
| Cd | n=3 | 5–80 | medium | 1 |
| iAs | data gap | — | — | — |
| tAs | n=1 | 5–50 | low | — |
| tHg | n=2 | 0–10 | low | 1 |
| Ni | n=1 | — | — | — |
| Al | n=1 | — | — | — |
| Cr | n=1 | — | — | — |
| Sn | data gap | — | — | — |
| U | data gap | — | — | — |
Ranges by source, region, and variety
The Polish Winiarska-Mieczan 2023 dataset (n=432) is the most species-diverse fresh-herbs dataset in the loaded corpus, covering common Polish-cuisine herbs and single-component spices in their fresh and dried forms; the work confirms the fresh-vs-dried-basis factor of ~7-10× concentration on a per-mass basis (The Content of Cd and Pb in Herbs and Single-Component Spices Used in Polish Cuisine). The Australian LHAAC 2025 CSP 41 covers both fresh and dried product across n=380 retail-and-import samples with the 7-metal panel (Coordinated Sampling Project 41: Microbial and Heavy Metal Detections in Herbs and Spices). The Fischer 2022 Polish mercury-in-spice-plants work (n=48 fresh-leaf samples) is the most species-specific tHg data for fresh herbs (The Mercury Concentration in Spice Plants). Species-level variance is substantial: parsley, dill, chives, and basil sit at the lower end of the fresh-herb Pb-and-Cd distribution; sage, lemon balm, and chamomile sit at the higher end (mirroring the dried-herb pattern); thyme, oregano, mint sit at the middle. Siting matters more than species for the Pb pathway specifically: roadside-grown parsley can carry more Pb than commercially-grown lemon balm grown on Mediterranean cropland away from atmospheric sources.
Processing effects
Drying is the major processing transition for fresh herbs, with fresh-to-dried producing the 7-10× per-mass concentration uplift documented above. The transition is well-characterised and is a basis change rather than contamination. Washing fresh herbs before consumption removes surface particulate Pb (the atmospheric-deposition fraction) but does not affect internalised Cd, Cr, or Ni. Blanching and freezing (used for some processed fresh-herb products) loses small fractions of soluble Cd and Cr to the blanch water. Chopping and mincing do not affect the per-mass metal load. Herb purees and pestos concentrate the per-mass metal load proportional to the moisture-removal during processing.
Ingredient-derivative risk
Fresh whole-leaf herbs represent the baseline. Bagged or packaged fresh-herb product carries the same per-mass load with surface contamination reduced. Frozen herbs lose a small fraction of soluble metals to the freezing-and-blanching step. Herb pestos (basil pesto, parsley pesto, cilantro chutney) concentrate metals on a per-mass basis through moisture removal. Herb-infused oils carry a much smaller fraction of the parent herb’s metal load because most metals partition with the solid residue rather than the oil phase. Herb-infused vinegars and herb teas extract a fraction of the parent herb’s soluble metals into the liquid; per-serving exposure tracks the herb mass and the extraction efficiency.
Mitigation options
Sourcing levers
Source from production regions and operations with documented soil-and-water screening, away from roadsides and industrial corridors. For home-gardeners and urban-gardeners, soil testing before planting is the upstream intervention. Specify commercially-grown Mediterranean-origin product for the lower-end of the distribution.
Agronomic levers
Soil pH management around 6.5 reduces Cd bioavailability. Avoidance of phosphate fertilisers with elevated Cd impurity reduces Cd loading. For brand-controlled-supply operations, raised-bed and container-growing with imported clean substrate eliminates the inherited-soil Pb pathway.
Processing levers
Washing reduces surface Pb but not internalised metals. Drying concentrates metals on a per-mass basis (basis change, not contamination). Avoid extended storage in unsealed bulk where atmospheric Pb dust deposition can accumulate.
Formulation levers
For finished-product applications using fresh herbs as one ingredient, the inclusion ratio caps per-serving exposure. Substitution between fresh-herb species shifts the per-mass profile modestly.
Testing and QC levers
Lot-level ICP-MS testing for Pb (detection floor ≤ 10 ppb fresh-weight) and Cd (≤ 5 ppb fresh-weight) is appropriate for commercial fresh-herb buyers, with conversion to dry-weight equivalent reporting where the downstream product is dried.
Packaging and storage levers
Packaging is not the dominant pathway for fresh herbs. Standard food-grade clamshell and bag packaging do not affect the metal load.
Regulatory limits that apply
The Codex Alimentarius General Standard CXS 193-1995 applies the leafy-vegetable Pb maximum of 0.30 mg/kg fresh weight to fresh herbs, and Cd at 0.20 mg/kg fresh weight (general vegetables; some fresh herbs fall under specific tighter categories). The EU Regulation 2023/915 applies tighter limits: 0.30 mg/kg Pb for “leafy vegetables and fresh herbs,” and 0.20 mg/kg Cd for leafy vegetables and stems excluding celery and salsify. The Australian LHAAC 2025 CSP 41 found commercial fresh-herb product generally compliant with applicable Australian caps on a fresh-weight basis (Coordinated Sampling Project 41: Microbial and Heavy Metal Detections in Herbs and Spices). The Polish Winiarska-Mieczan 2023 work confirmed similar compliance for the Polish-market fresh-herb category (The Content of Cd and Pb in Herbs and Single-Component Spices Used in Polish Cuisine).
References
Works cited in this page’s text, in first-appearance order. This is not the full corpus for this page; it is only what the prose above draws on. The complete set of sources is listed under Sources below. Each title links to its source record, which carries the ingest receipt, the extracted values, and the file hash of the document it was built from.
- The Mercury Concentration in Spice PlantsReview
- Coordinated Sampling Project 41: Microbial and Heavy Metal Detections in Herbs and SpicesGovernment
- The Content of Cd and Pb in Herbs and Single-Component Spices Used in Polish CuisineReview
Sources
Auto-generated from source-page frontmatter. The "Used on this page for" column is populated by the orchestrator's POPULATE-SOURCE-LEGEND action; pending entries appear as *[awaiting synthesis]*.
| # | Citation | Year | Type | Used on this page for |
|---|---|---|---|---|
| 1 | Winiarska-Mieczan et al. 2023. The Content of Cd and Pb in Herbs and Single-Component Spices Used in Polish Cuisine, Biological Trace Element Research | 2023 | Peer-reviewed | Polish fresh-and-dried herb Cd-Pb panel (n=432); largest single-jurisdiction dataset establishing fresh-vs-dried-basis factor |
| 2 | Fischer et al. 2022. The Mercury Concentration in Spice Plants, Processes | 2022 | Peer-reviewed | Polish mercury in 48 fresh-leaf spice-plant samples; strongest tHg data |
| 3 | Souri et al. 2019. Plant growth stage influences heavy metal accumulation in leafy vegetables of garden cress and sweet basil, Chemical and Biological Technologies in Agriculture | 2019 | Peer-reviewed | IR Cd, Pb, Ni, tAs, Cr, Co, Cu, Mn, Zn occurrence in Garden cress and sweet basil from five wastewater-irrigated farms in Shahre Rey, south of Tehran, Iran; field samples… (n=5) |
| 4 | Ghasemidehkordi et al. 2018. Concentration of lead and mercury in collected vegetables and herbs from Markazi province, Iran: a non-carcinogenic risk assessment, Food and Chemical Toxicology 113:204-210 | 2018 | Peer-reviewed | IR Pb, tHg occurrence in Ten species of green leafy vegetables and herbs (Allium ampeloprasum L. [leek], A. wakegi L. [Welsh/Japanese bunching onion],… (n=160) |
| 5 | Salehipour et al. 2015. Health Risks from Heavy Metals via Consumption of Cereals and Vegetables in Isfahan Province, Iran, Human and Ecological Risk Assessment: An International Journal | 2015 | Peer-reviewed | IR Pb, tAs, Ni, Zn, Cu occurrence in Seventy edible-part samples of nine commodities — onion (Allium cepa), leek (Allium pp.; species not stated by authors),… (n=70) |
| 6 | Kazimov et al. 2014. Examination and Hygienic Assessment of Health Risk Depending on Heavy Metals Content in Foods, Kazanskiy Meditsinskiy Zhurnal (Kazan Medical Journal), vol. 95, no. 5, pp. 706–709 | 2014 | Peer-reviewed | AZ Pb, Cd, Cr, Ni, Cu, Zn occurrence in 57 adults (28 men, 29 women, age 19–49) sampled by random selection from Baku, Azerbaijan; 18 food items… (n=57) |
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and 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.
| Commit | Date | Change | Description |
|---|---|---|---|
| e317189 | 2026-08-11 | correction | 3 sources added; contamination-profile values revised; 17 sections added |