Teferi et al. 2026 — Heavy metal contamination and health risks in honey from Kellem Wollega Zone, Ethiopia

Honey samples from three districts in the Kellem Wollega Zone of western Ethiopia were analyzed for seven metals (Cu, Fe, Mn, Ni, Zn, Cd, Pb) by ICP-OES after wet acid digestion. Cadmium concentrations (1.38–2.30 mg/kg) and lead concentrations (18.00–21.42 mg/kg) far exceeded the EU maximum limit for Cd in honey (0.05 mg/kg per Regulation (EU) 2023/915) and the Codex Alimentarius maximum for Pb (0.1 mg/kg). Non-carcinogenic hazard indices remained below 1.0 across all sites, indicating no immediate chronic toxic risk at typical honey consumption rates, but cumulative carcinogenic risk values (1.32 × 10⁻³ at Dambi Dollo) exceeded the 1 × 10⁻⁴ benchmark, with nickel as the dominant contributor to total cancer risk. The study is the first to provide a baseline heavy-metal dataset for honey from this zone, identifying artisanal gold mining in Anafilo and agricultural chemical use as primary contamination drivers.

Key numbers

All concentrations in mg/kg wet weight, mean ± SD, n = 3 composite samples (one per district; each composite from five apiary subsamples). Source: Table 4, p. 7.

Reported concentration order across the study: Zn > Fe > Pb > Mn > Cu > Ni > Cd (paper abstract; site-by-site rankings: Cu, Fe, Mn, Ni, Cd rank Dambi Dollo > Gawo Kebe > Anafilo; Zn ranks Anafilo > Gawo Kebe > Dambi Dollo; Pb ranks Anafilo > Gawo Kebe > Dambi Dollo).

Pb levels showed no statistically significant difference across sites (p > 0.05, one-way ANOVA); all other metals showed significant site differences (p < 0.05, Tukey HSD).

Method LOQ (ICP-OES, mg/L; Table 2 p. 5): Cu 0.057, Fe 7.157, Mn 0.185, Ni 0.114, Cd 0.327, Zn 3.735, Pb 1.576. Spike recovery rates 89.09–114.82%; replicate %RSD 0.12–1.35%.

Health risk (adult, IR = 5.5 g/day, BW = 67 kg, ED = 70 yr; Table 6 p. 11):

• Hazard Index (HI): Dambi Dollo 8.10 × 10⁻¹, Gawo Kebe 7.94 × 10⁻¹, Anafilo 7.86 × 10⁻¹ (all < 1; non-carcinogenic risk not significant)
• Total Cancer Risk (∑TCR): Dambi Dollo 1.32 × 10⁻³, Gawo Kebe 1.21 × 10⁻³, Anafilo 9.08 × 10⁻⁴ (Dambi Dollo and Gawo Kebe exceed the 1 × 10⁻³ threshold and fall in the NYSDOH “high” risk category; Anafilo is in the “moderate” range but still above the 1 × 10⁻⁴ regulatory benchmark)
• Ni dominates carcinogenic risk at all sites (TCR range 8.50 × 10⁻⁴ to 1.23 × 10⁻³); Cd secondary (4.29 × 10⁻⁵ to 7.18 × 10⁻⁵); Pb contributes primarily to non-carcinogenic hazard (THQ 0.422–0.506) rather than cancer risk (TCR 1.27 × 10⁻⁵ to 1.50 × 10⁻⁵)

Methods (brief)

Fifteen honey subsamples were collected from five apiary points per district (five-point cluster sampling design) and composited into three samples for analysis. Samples were stored at 4 °C and gently liquefied in a 4 °C water bath prior to digestion. Wet acid digestion used HNO₃ (65–68%) and HClO₄ (70%) at 2:1.5 v/v (UNI-CHEM, Mumbai, India), 0.5 g sample with 3.5 mL acid mixture, in a Kjeldahl block at 160–240 °C (240 °C optimum) under reflux for 2 h 45 min. Digests were filtered through Whatman No. 41 paper, diluted to 100 mL with deionized water, then diluted 1:10 before ICP-OES measurement. ICP-OES instrument: PerkinElmer Optima 8000 (1500 W RF, 10 L/min plasma gas, 0.7 L/min nebulizer, three replicates per sample, Table 1 p. 4). Method validation by spike recovery and replicate %RSD (Table 3 p. 5–6); calibration with certified multi-element standard (Buck Scientific PuroGraphic, 1000 mg L⁻¹ in 2% HNO₃). The study measured only Cu, Fe, Mn, Ni, Zn, Cd, and Pb; no arsenic, mercury, or tin measurement and no speciation. All reported values are total metal.

Implications

Certification: Pb at 18.00–21.42 mg/kg and Cd at 1.38–2.30 mg/kg are 180–214× and 28–46× above the Codex Pb limit (0.1 mg/kg) and EU 2023/915 Cd limit (0.05 mg/kg) for honey, respectively. The paper provides important geographic-range data showing African artisanal-mining-impacted regions as extreme honey contamination hotspots; values from this corpus should not be pooled with low-contamination-region distributions without site-stratification.

Courses: Demonstrates the biomonitoring utility of honey for regional environmental contamination assessment. The divergence between non-carcinogenic risk (HI below 1 at all three sites under standard 5.5 g/day intake) and carcinogenic risk (∑TCR above the 1 × 10⁻⁴ benchmark at all three sites) illustrates why USEPA-style risk frameworks with hazard quotients and cancer-slope-factor multiplications yield different conclusions for the same contamination level.

App: The extreme Pb and Cd values reported here are outliers at the high end of the global honey distribution; representing them as typical for “honey” without a geographic qualifier (artisanal-mining-impacted region, Ethiopia) would misstate background risk substantially.

Wiki pages updated on ingest

• honey
• lead
• cadmium
• nickel
• eu-2023-915-cadmium

Verification notes

Merge-enhance pass 2026-05-20 (Claude Opus 4.7, autonomous ingest cycle):

• Corrected transposed Table 4 values. Prior revision (2026-05-13) had the seven-metal × three-site table rotated by one column: the Dambi Dollo column held Gawo Kebe’s values, the Gawo Kebe column held Anafilo’s values, and the Anafilo column held Dambi Dollo’s values. Verified each cell against Table 4 (p. 7) of the source PDF; values now match the paper. Re-checked against the paper’s prose rankings on p. 9 (“Cu, Fe, Mn, Ni, and Cd ranked Dambi Dollo > Gawo Kebe > Anafilo; Zn, Anafilo > Gawo Kebe > Dambi Dollo; and Pb, Anafilo > Gawo Kebe > Dambi Dollo”). The corrected table is now internally consistent with the paper’s reported rankings.
• Corrected truncated raw_path. Prior raw_path ended at “Associated Health Ris.pdf”; actual file name is “Associated Health Risks in Honey from Kellem Wollega Zone, Ethiopia.pdf”. Fixed.
• Corrected regulation wikilink. Prior [[regulations/eu-2023-915]] is not a valid slug; the wiki page is [[regulations/eu-2023-915-cadmium]]. Fixed.
• Expanded Methods (brief) with instrument vendor/model (PerkinElmer Optima 8000), digestion parameters, calibration standard (Buck Scientific PuroGraphic), and filter (Whatman No. 41) per the verification-checklist Exception 2 for scientific-method vendor naming. Speciation status (none performed; all values are total metal) made explicit.
• Expanded Key numbers with Ni and Cd TCR ranges, Pb THQ range, and source-citation page numbers for the audit trail.
• Preserved cite_key, raw_handle, license, frontmatter slugs (all in taxonomy snapshot), and the overall page structure.

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.