Fischer and Brodziak-Dopierała 2022 — Mercury in Polish spice plants: commercial vs. home-grown

This Medical University of Silesia study measured total mercury (tHg) in 48 dried leafy-spice samples comprising four species — peppermint (Mentha piperita), common basil (Ocimum basilicum), lovage (Levisticum officinale), and parsley (Petroselinum crispum) — comparing commercially purchased Polish products (n=28; 24 non-organic and 4 producer-certified organic) with plants grown by consumers in home gardens at five locations in southern Poland (n=20). Detection was by cold-vapour AAS on an AMA 254 direct mercury analyzer. All samples were below the EU maximum level of 0.03 mg/kg (30 µg/kg) for mercury in deciduous spice plants. Self-cultivated plants had statistically significantly higher Hg concentrations than commercial products (p < 0.001), while producer-labelled organic vs. non-organic commercial products showed no significant difference. Among home-grown samples, location influenced Hg level, with plants from Płoki (Małopolskie voivodeship, near a coal-fired power plant and closed hard-coal mine) showing the highest concentrations across species.

Key numbers

All concentrations in µg/kg dry weight, total mercury.

All samples combined (n=48):

• Range: 1.20–17.35 µg/kg
• Mean ± SD: 6.95 ± 3.70 µg/kg
• Median (Q1–Q3): 6.17 (4.58–8.83) µg/kg

By species (Table 2):

• Peppermint (n=10): mean 9.39 ± 5.83 µg/kg; median 9.58 (Q1–Q3 2.40–14.18) µg/kg
• Parsley (n=12): mean 6.72 ± 2.39 µg/kg; median 6.40 (Q1–Q3 5.83–7.64) µg/kg
• Basil (n=15): mean 6.19 ± 2.08 µg/kg; median 5.52 (Q1–Q3 4.72–7.24) µg/kg
• Lovage (n=11): mean 6.02 ± 3.67 µg/kg; median 5.27 (Q1–Q3 3.08–8.27) µg/kg
• Species differences not statistically significant (Kruskal–Wallis p = 0.2968)

By product type (Table 2):

• Commercial products (n=28): mean 5.15 ± 2.58 µg/kg; median 4.99 (Q1–Q3 3.23–6.54) µg/kg
• Home-grown (n=20): mean 9.47 ± 3.58 µg/kg; median 8.70 (Q1–Q3 6.38–11.55) µg/kg
• Difference statistically significant (Mann–Whitney U p < 0.001; reported p = 0.00003)

Commercial sub-comparison (Table 2):

• Non-organic (n=24): mean 5.20 ± 2.64 µg/kg; median 4.99 (Q1–Q3 3.65–6.19) µg/kg
• Producer-certified organic (n=4): mean 4.88 ± 2.56 µg/kg; median 4.91 (Q1–Q3 2.69–7.07) µg/kg
• Difference not statistically significant (p = 0.97381)

Per-species means within each product type (text §3):

• Commercial: parsley 6.03, basil 5.43, lovage 3.23, peppermint 2.40 µg/kg
• Home-grown: peppermint 14.18, lovage 8.27, parsley 7.62, basil 6.00 µg/kg
• Within-species commercial-vs-home-grown differences were statistically significant only for lovage and peppermint

By growing location, home-grown only (text §3 + Figure 3):

• Highest median across species: Płoki (Małopolskie, near coal-fired power plant and closed hard-coal mine), median ≈ 12.90 µg/kg across all four species
• Lowest median across species: Jemielnica (Opolskie, rural, no major industrial sources)
• Rural Jastrząb (Śląskie) was comparable to urban Katowice/Mysłowice and lower than rural Płoki, indicating that rural-vs-urban location does not predict Hg burden on its own
• Highest individual location-species values at Płoki: parsley 12.19 µg/kg (the maximum parsley value in the home-grown set, range 5.76–12.19 µg/kg)
• Home-grown sample range overall: 4.98–17.35 µg/kg (text §4)

EU regulatory context:

• Commission Regulation (EU) 2018/73 (amending Annexes II and III of Reg. (EC) 396/2005): maximum mercury residue level in leafy spice plants (deciduous herbs) = 0.03 mg/kg = 30 µg/kg
• All 48 samples were below the limit (observed maximum 17.35 µg/kg in a home-grown peppermint sample)

Estimated daily intake (EDI), authors’ calculation (text §4):

• Assumed consumption 0.7 g/day spices and herbs (Polish average; Kowalska 2021); adult body weight 70 kg
• Home-grown: EDI = 9.47 µg/kg × 0.7 g/day ÷ 70 kg ≈ 9.47 × 10⁻⁵ mg Hg/kg bw/day
• Commercial: EDI = 5.15 µg/kg × 0.7 g/day ÷ 70 kg ≈ 5.15 × 10⁻⁵ mg Hg/kg bw/day
• Both values are below the JECFA PTWI for inorganic mercury (4 µg/kg bw/week, equivalent to ≈ 5.7 × 10⁻⁴ mg/kg bw/day); authors conclude Polish dietary spice consumption does not constitute a mercury risk

Methods (brief)

Direct mercury analyzer AMA 254 (Altec, Praha, Czech Republic): catalytic combustion thermal-decomposition cold-vapour atomic absorption at 253.65 nm with O₂ carrier gas (purity ≥ 99.5%, inlet 200–250 kPa; stage times 120, 140, 60 s). LOD 0.01 ngHg/g (i.e. 0.01 µg/kg). Method covers total Hg regardless of speciation. Each spice sample was prepared as three ~50 mg replicate weighings on a RADWAG analytical balance (Radom, Poland); final reported value is the arithmetic mean of three measurements. Home-grown plant material was air-dried at room temperature in a shaded room, then ground in a porcelain mortar; commercial products were ground identically. Method validation used the INCT-MPH-2 Mixed Polish Herbs reference material (Institute of Nuclear Chemistry and Technology, Warsaw): six replicate determinations gave 0.0166 ± 0.0001 mg/kg with 92.22% recovery against the certified value. Statistical analysis used Statistica 13.3 (StatSoft, Kraków): Shapiro–Wilk normality testing, Mann–Whitney U (two groups), Kruskal–Wallis (more than two groups), p < 0.05 two-tailed.

Study limitations: small group sizes (notably n=4 organic commercial samples; n=20 home-grown samples spread across five locations and four species, leaving only one replicate per species per location); restricted to four species and southern-Poland growing locations; commercial-product origin not characterised beyond “popular Polish-market producers”; no speciation (total Hg only); single-season harvest (June, mid-growing-season) so seasonal accumulation effects reported in cited prior work were not captured.

Implications

Certification: Contributes occurrence data for leafy culinary herbs (peppermint, basil, lovage, parsley) and for the commercial-vs-home-grown comparison, in a Polish/EU regulatory context. Across this dataset, total Hg in dried leafy herbs sat well below the EU 30 µg/kg residue limit, with the observed maximum (17.35 µg/kg, home-grown peppermint) at approximately 58% of the limit. The commercial-vs-home-grown gap (mean 5.15 vs 9.47 µg/kg) is the principal occurrence finding for supplier-context purposes; the producer-labelled “organic” vs. non-organic commercial subset showed no statistically significant Hg difference within this study’s small organic subsample (n=4).

Courses: Adds an example for course material on the relationship between certification labelling and contamination outcome: within this study’s commercial subset, the producer-labelled “organic” subsample (n=4) did not differ statistically significantly in Hg content from non-organic commercial products (n=24). Adds a worked EDI calculation (authors’ method) for spice intake at Polish per-capita consumption (0.7 g/day).

App: Provides total-Hg occurrence values for four leafy herb species in Polish/EU supply context. Cultivation-origin metadata (commercial vs. home-grown, near vs. far from coal-fired industrial point sources) is informative for app-side scoring of provenance categories where reported.

Verification notes

2026-05-29 merge-enhance pass (v2.0 skill): re-read PDF cover-to-cover including all tables.

• Corrected broken regulation wikilink: [[regulations/eu-reg-2018-73-mercury-herbs]] → [[regulations/eu-reg-2018-73-mercury-compounds-mrls]] (the existing regulation page slug).
• Corrected misattribution of the 12.90 µg/kg figure: prior page text “Płoki … e.g., peppermint up to 12.90 µg/kg” implied 12.90 was a peppermint-specific value. Per paper page 5, “Hg concentration was the highest for all plants (12.90 µg/kg)” — this is the location median across all four species at Płoki (visible in Figure 3), not a peppermint-specific value. The peppermint maximum at any location is captured by the home-grown peppermint mean of 14.18 µg/kg (text §3) and the overall range maximum of 17.35 µg/kg.
• Removed fresh-herbs from matrices:: all 48 samples (both commercial and home-grown) were measured as dried plant material (home-grown samples were air-dried at room temperature before grinding and analysis, paper page 3). dried-herbs and spices better describe what was measured; fresh-herbs is retained as an ingredients: wikilink because the home-grown subset documents fresh-grown supply that was then dried for the analysis.
• Added [[ingredients/parsley]] to ingredients:: parsley has a dedicated wiki ingredient page and this paper provides species-specific parsley data (n=12, mean 6.72 µg/kg overall and 12.19 µg/kg maximum at Płoki).
• Populated sampling_locations: from Table 1 (Katowice, Mysłowice, Jastrząb in Śląskie voivodeship; Płoki in Małopolskie; Jemielnica in Opolskie).
• Trimmed Part 2 wiki/HMTc-firewall slips in ## Implications: removed an HMTc operational directive (“brands sourcing fresh herbs from contract growers in industrially contaminated regions should include Hg testing in their QC protocols”); removed a synthesis claim (“a recurring theme in heavy-metals literature”); reframed consumer-risk wording as neutral occurrence-data contribution per Part 2.
• Paper-internal labelling discrepancy noted, not flagged as a wiki error: paper page 8 reports “For the tested cultivated plants, the EDI value was 0.0000515 mg/kg/day, and in the group of commercial products it was 0.0000947 mg/kg/day” — but the underlying means (Table 2: cultivated 9.47 µg/kg, commercial 5.15 µg/kg) imply the reverse assignment, and EDI = concentration × intake / bw confirms cultivated → 0.0000947 and commercial → 0.0000515. The wiki page assigns EDI values to the group that matches each group’s reported mean; the paper text has the two labels switched.
• Paper-internal location-naming discrepancy noted: Table 1 lists five collection points (Katowice, Mysłowice, Jastrząb, Płoki, Jemielnica), but Figure 3 plots a slightly different five-name set (Dąbrówka Mała, Mysłowice, Płoki, Poraj, Jemielnica). Treated as the paper’s own inconsistency; not amended on the wiki page.

Wiki pages updated on ingest

• herbs-and-spices
• dried-herbs
• fresh-herbs
• parsley
• mercury
• eu-reg-2018-73-mercury-compounds-mrls

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.