Wise et al. 2025 — Elevated metal levels in U.S. honeys

Twenty elements were measured in 28 U.S. honey samples from 15 states using benchtop X-ray fluorescence (XRF), which the authors describe as the most geographically broad survey of metal contaminants in U.S. honeys reported to date. The majority of samples exceeded EU maximum residue levels for lead (0.10 µg/g) and mercury (0.01 µg/g), with the highest Pb observed in Tennessee (0.918 µg/g), Massachusetts (0.820 µg/g), and New Mexico (0.367 µg/g), and the highest Hg in Massachusetts (8.94 µg/g), Tennessee (7.04 µg/g), and New Mexico (6.92 µg/g) — 894×, 704×, and 692× the EU MRL respectively. Estimated weekly intake calculations at 300 mg honey/kg body mass/day showed that all four toxic metals (As, Pb, Cd, Hg) and aluminum exceeded JECFA provisional tolerable weekly intake (PTWI) values, with Hg EWI of 2.504 mg/kg body mass/week against a PTWI of 0.005 mg/kg (≈501× excess). The paper contains several internal inconsistencies in the Cd reporting (see Key numbers).

Key numbers

U.S. honey concentrations from Table 2 (mg metal/kg honey, equivalent to µg/g):

EWI assumes 300 mg honey/kg body mass/day (≈15.3 mL or 1.03 US tablespoons for a 70-kg adult), the dose commonly used in honey therapeutic studies (paper Methods, Estimated Weekly Intake section).

Mean ± SEM concentrations for 13 metals detected in all 28 honeys (paper Results, p. 1793):

Sodium 406.8 ± 1.58 µg/g; Calcium 234.8 ± 2.15 µg/g; Zinc 75.9 ± 12.18 µg/g; Iron 31.33 ± 7.23 µg/g; Bromine 4.82 ± 0.45 µg/g; Copper 3.61 ± 0.01 µg/g; Manganese 2.33 ± 0.37 µg/g; Selenium 0.51 ± 0.03 µg/g; Silicon 0.19 ± 0.02 µg/g; Gallium 0.14 ± 0.01 µg/g; Titanium 0.056 ± 0.039 µg/g; Germanium 0.035 ± 0.01 µg/g; Vanadium 0.021 ± 0.004 µg/g. (The Discussion section reports Sodium 406.8 ± 8.3 µg/g and Calcium 234.8 ± 11.35 µg/g — paper-internal SEM discrepancies; means are consistent across both presentations.)

Highest values by state (µg/g), from paper Results & Discussion (p. 1793):

• Pb: Tennessee 0.918, Massachusetts 0.820, New Mexico 0.367 (EU MRL = 0.10; ratios 9.18×, 8.2×, 3.67×)
• Cd: paper text gives “Tennessee 0.918, Massachusetts 0.820, Vermont 0.350” — values for TN and MA are an exact duplicate of the Pb top-two and are clearly a copy-paste editorial error in the source; Fig 2B shows the Cd y-axis ranging 0.005–0.020 µg/g, and the Table 2 Cd EWI of 0.027 mg/kg body mass/week implies a true Cd mean of ≈0.013 mg/kg honey (paper-internal contradiction — see Verification notes)
• Hg: Massachusetts 8.94, Tennessee 7.04, New Mexico 6.92 (EU MRL = 0.01; ratios 894×, 704×, 692×)
• As: Oregon 0.067, Indiana 0.065, Arkansas 0.065 (EU has no honey-specific iAs/tAs MRL)

Fig 1 element-range groupings (paper Results): Eleven metals in 0–1 µg/g range (Mg, Si, Ti, V, Cr, As, Se, Pb, Cd, Ga, Ge); four in 1–15 µg/g (Mn, Cu, Br, Hg); three in 0–300 µg/g (Al, Fe, Zn); two in 200–500 µg/g (Na, Ca). The paper reports levels of 20 elements total; thirteen of those were detected in all 28 honeys.

States sampled (n samples): Arkansas (2), Florida (2), Indiana (2), Kentucky (4), Maine (1), Maryland (1), Massachusetts (2), New Mexico (4), North Carolina (1), Oklahoma (1), Oregon (2), Tennessee (3), Texas (1), Vermont (1), West Virginia (1) — 28 samples across 15 states. (The paper Methods opening states “14 different states” in passing; Table 1 and the abstract both correctly enumerate 15.)

Methods (brief)

Benchtop XRF (Epsilon 4, Malvern Panalytical, Marlborough, MA) with 15-W X-ray tube at 50 kV maximum and 300 µA, 7.5-minute collection per sample. Honey samples were placed undigested and unhomogenized in 30-mm XRF cups covered with 4-µm polypropylene film. Quantification used Epsilon 4 software deconvolution (gaussian + polynomial background) and calibration against phantom samples doped with known metal concentrations across a thickness/mass range; Compton scattering peak normalization corrected for sample mass and thickness variation. Reported in µg/g, the standard ICP-MS unit. ArcGIS Pro 3.2.2 used for state-level mapping with zip-code-centered coordinates.

The EWI formula reported by the authors is: EWI = (daily honey consumption × metal concentration / body mass) × 7, with daily honey consumption of 300 mg/kg body mass per day and adult body mass of 70 kg (yielding ≈21 g honey/day). The Table 2 EWI values are internally consistent with the stated formula for As, Pb, and Cd if the Cd “US Honey Mean” is read as 0.013 rather than the printed 0.132 (see Verification notes); the Hg EWI of 2.504 mg/kg/week is high but lower than a strict formula application to the stated Hg mean of 3.710 mg/kg would predict.

Method limitations stated or implied by the paper: XRF does not speciate arsenic, so the reported values are total As (tAs), not iAs. XRF is less sensitive for Hg than ICP-MS; the unusually high Hg values (up to 8.94 µg/g) are notable and would benefit from independent ICP-MS verification, which the authors do not provide. The paper does not report method-specific LODs/LOQs, recovery percentages, or analytical replicates per sample. No certified reference material results are reported in the main text. Citizen-science benchtop-XRF validation citations are provided for related applications (toenails, soil, blood) but not for honey specifically.

Implications

Certification: U.S. honey has no federal maximum contaminant levels for metals; the EU maximum residue level for Pb in honey (Commission Regulation 2023/915) is 0.10 µg/g and for Hg (Commission Regulation 2018/73 amending Reg. EC 396/2005) is 0.01 µg/g. The majority of samples in this study exceed both. This is directly relevant to the HMT&C analyte panel for honey, if honey or honey-containing products fall within program scope: the literature demonstrates that commercial small-batch U.S. honey frequently fails EU standards for Pb and Hg. The arsenic values here are total As (tAs); a speciation study would be needed to determine the inorganic As (iAs) fraction relevant to the HMT&C iAs threshold.

Courses: The XRF methodology illustrates a non-destructive, no-digestion screening approach that enables broad geographic survey but cannot differentiate metal species. The contrast between the high estimated weekly intakes and typical honey consumption patterns (most adults do not consume 15 mL/day as a therapeutic dose) demonstrates how exposure scenario assumptions dominate health-risk calculations. The paper’s several internal arithmetic inconsistencies (Cd state values, Cd mean vs Cd EWI, SEM discrepancies between Results and Discussion) make it a useful teaching case for source-level quality criticism within evidence synthesis.

App: State-level variation suggests honey from Tennessee, Massachusetts, and New Mexico carries higher risk for Pb and Hg, with smaller-magnitude elevations across most sampled states. The absence of US federal regulatory limits for metals in honey means the app should cite the EU MRLs as comparison benchmarks rather than domestic regulatory exceedances. Total As at mean 0.060 µg/g is at the low end of the food-matrix arsenic range; the iAs fraction is unknown from XRF measurement.

Wiki pages this source may touch

• honey
• lead
• cadmium
• arsenic-total
• mercury-total
• aluminum
• copper
• manganese
• zinc
• iron
• eu2023-contaminants-maximum-levels
• eu-reg-2018-73-mercury-compounds-mrls

Verification notes

Merge-enhance pass 2026-05-20 (Claude Opus 4.7, autonomous ingest cycle; existing page updated: 2026-05-13 predated the 2026-05-14 schema cutoff):

• Removed invalid wikilinks. Prior revision referenced [[regulations/eu-2023-915]], [[metals/tAs]], and [[metals/tHg]]. None of these slugs exist in the current taxonomy (see docs/gpt-collaboration/taxonomy-snapshot.md). The EU 2023/915 reference is now [[regulations/eu2023-contaminants-maximum-levels]] (the umbrella regulation page); the Hg honey MRL of 0.01 mg/kg is set under Commission Regulation (EU) 2018/73 amending Annexes II and III to Reg. EC 396/2005, and the matching slug [[regulations/eu-reg-2018-73-mercury-compounds-mrls]] is now linked. tAs and tHg metal references corrected to [[metals/arsenic-total]] and [[metals/mercury-total]].
• Removed Ni from metals: frontmatter. The prior revision listed Ni; the paper does not measure Ni. Per the paper’s own Fig 1 grouping, the 20 elements reported are Mg, Si, Ti, V, Cr, As, Se, Pb, Cd, Ga, Ge (Fig 1A), Mn, Cu, Br, Hg (1B), Al, Fe, Zn (1C), and Na, Ca (1D). Ni is not in the panel.
• Flagged paper-internal Cd values as a copy-paste editorial error. Paper Results & Discussion (p. 1793) states “The three highest levels of Cd were observed in honeys from Tennessee (0.918 µg/g), Massachusetts (0.820 µg/g), and Vermont (0.350 µg/g)” — TN and MA values are exact mirrors of the Pb top-two stated in the immediately preceding sentence. Fig 2B shows Cd y-axis from 0.005 to 0.020 µg/g, which is incompatible with values approaching 1 µg/g. The corrected page reports the paper’s stated values verbatim but flags them as a clear source-internal copy-paste error, as required for faithful reporting of a defective primary source.
• Flagged Cd mean / EWI inconsistency. Table 2 reports Cd “US Honey Mean” of 0.132 mg/kg honey and Cd Weekly Metal Consumption of 0.027 mg/kg body mass/week. Applying the paper’s stated EWI formula (300 mg honey/kg body mass/day × concentration × 7 days, with the kg-conversion absorbed appropriately) to a Cd mean of 0.132 gives an EWI of ≈0.277 mg/kg/week — ten times the printed Cd EWI. The printed Cd EWI of 0.027 is consistent with a true Cd mean of ≈0.013 mg/kg, which matches Fig 1A and Fig 2B. The Table 2 Cd US Honey Mean of 0.132 appears to be a unit/decimal error in the source. The wiki reports both values verbatim and notes the discrepancy.
• Removed the previous Hg “discrepancy” note about 3.710 µg/g vs 2.504 mg/kg body mass. Those quantities are not contradictory: 3.710 mg/kg honey is a concentration in the matrix; 2.504 mg/kg body mass/week is a normalized weekly intake derived from concentration, daily honey dose, and body mass. The prior note misread the table headers. Replaced with a Methods-section observation that the Hg EWI is lower than a strict formula application to the stated Hg mean would predict (a separate, smaller paper-internal arithmetic inconsistency).
• Sample population breakdown corrected to Table 1. Prior sample_population summarized “20 wildflower, 2 tupelo, plus individual samples of sourwood, peach flower, star thistle, Russian olive, blackberry/blueberry, and turnip” — this matches the paper abstract but Table 1 actually lists 19 wildflower entries plus a “Desert flower” (NM) that the abstract omits. The corrected sample_population enumerates the Table 1 floral-source labels by state and flags the abstract-vs-Table-1 inconsistency.
• Updated ## Wiki pages this source may touch to include all metals with reported means in the paper (Al, Cu, Mn, Zn, Fe in addition to the previously listed Pb/Cd/As/Hg) and both relevant regulation pages. Renamed section heading from ## Wiki pages updated on ingest (legacy) to ## Wiki pages this source may touch (current convention).
• Tightened the Key numbers section into a unified Table 2 view (toxic + essential metals together with EWI and PTWI ratios) plus a separate full mean ± SEM block for the 13 metals detected in all 28 honeys, replacing the prior less-structured narrative listing.
• Added Methods detail on the EWI formula, body-mass assumption, ArcGIS mapping version, and Compton scattering normalization, all from the source.
• Preserved cite_key, raw_handle, raw_path, license, evidence_tier, doi, sample_n, and ingredient/product/matrix/jurisdiction frontmatter. No new ingredient, product, or regulation pages proposed; all referenced slugs exist in the current taxonomy.

Page history

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